 Section 1 of the Advance of Science. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. The Advance of Science in the Last Half Century by Th Huxley, 1889. The most obvious and the most distinctive features of the history of civilization during the last 50 years is the wonderful increase of industrial production by the application of machinery, the improvement of old technical processes, and the invention of new ones, accompanied by an even more remarkable development of old and new means of locomotion and intercommunication. By this rapid and vast multiplication of the commodities and conveniences of existence, the general standard of comfort has been raised, the ravages of pestilence and famine have been checked, and the natural obstacles which time and space offered to mutual intercourse have been reduced in a manner and to an extent unknown to former ages. The diminution or removal of local ignorance and prejudice, the creation of common interests among the most widely separated peoples, and the strengthening of the forces of the organization of the Commonwealth against those of political or social anarchy, thus affected, have exerted an influence on the present and future fortunes of mankind, the full significance of which may be divined but cannot as yet be estimated at its full value. This revolution, for it is nothing less, in the political and social aspects of modern civilization, has been preceded, accompanied, and in great measure caused by a less obvious but no less marvelous increase of natural knowledge, and especially of that part of it which is known as physical science. In consequence of the application of scientific method to the investigation of the phenomena of the material world. Not that the growth of physical science is an exclusive prerogative of the Victorian age, its present strength and volume merely indicate the highest level of a stream which took its rise alongside of the primal fonts of philosophy, literature, and art in ancient Greece, and after being dammed up for a thousand years once more began to flow three centuries ago. It may be doubted if even hinted justice, as free from fulsome panadryric as from capsious depreciation, has ever yet been dealt out to the sages of antiquity, who, for eight centuries from the time of tales to that of gallon, toiled at the foundations of physical science. But, without entering into the discussion of that large question, it is certain that the labors of these early workers in the field of natural knowledge were brought to a standstill by the decay and disruption of the Roman Empire, the consequent disorganization of society, and the diversion of men's thoughts from subliminary matters to the problems of the supernatural world suggested by Christian dogma in the Middle Ages. And notwithstanding sporadic attempts to recall men to the investigation of nature here and there, it was not until the fifteenth and sixteenth centuries that physical science made a new start, founding itself at first altogether upon that which had been done by the Greeks. Indeed, it must be admitted that the men of the Renaissance, those standing on the shoulders of the old philosophers, were a long time before they saw as much as their forerunners had done. The first serious attempts to carry further the unfinished work of Archimedes, Hipparchus, and Ptolemy, of Aristotle and of Galen, naturally enough arose among the astronomers and the physicians. For the imperious necessity of seeking some remedy for the physical ills of life had ensured the preservation of more or less of the wisdom of Hippocrates and his successors. And by a happy conjunction of circumstances, the Jewish and Arabian physicians and philosophers escaped many of the influences which, at that time, blighted natural knowledge in the Christian world. On the other hand, the superstitious hopes and fears which afforded countenance to astrology and to alchemy also sheltered astronomy in the germs of chemistry. Whether for this or for some better reason, the founders of the schools of the Middle Ages included astronomy, along with geometry, arithmetic, and music, as one of the four branches of advanced education. And in this respect, it is only just to them to observe that they were far in advance of those who sit in their seats. The school men considered no one to be properly educated unless you were acquainted with, at any rate, one branch of physical science. We have not, even yet, reached that stage of enlightenment. In the early decades of the 17th century, the men of the Renaissance could show that they had already put out to good interest the treasure bequeathed to them by the Greeks. They had produced the astronomical system of Copernicus with Kepler's great additions, the astronomical discoveries and the physical investigations of Galileo, the mechanics of Stevenus, and the de-magnet of Gilbert, the anatomy of the great French and Italian schools, and the physiology of Harvey, in Italy which had succeeded Greece in the hegamy of the scientific world, the Académie d'Alincie and sundry other associations for the investigation of nature, the models of all subsequent academies and scientific societies had been founded, while the literary skill and biting wit of Galileo had made the great scientific questions of the day not only intelligible but attractive to the general public. In our own country, Francis Bacon had a say to sum up the past of physical science and to indicate the path which it must follow if its great destinies were to be fulfilled. And though the attempt was just such a magnificent failure as might have been expected from a man of great endowments who was so singularly devoid of scientific insight that he could not understand the value of the work already achieved by the true insturators of physical science, yet the majestic eloquence and the fervid medicinations of one who was conspicuous alike by the greatness of his rise and the depth of his fall through the attention of all the world to the new birth of time. But it is not easy to discover satisfactory evidence that the novum organum had any direct beneficial influence on the advancement of natural knowledge. No delusion is greater than the notion that method and industry can make up for lack of mother wit, either in science or in practical life, and it is strange that with his knowledge of mankind Bacon should have dreamed that his or any other be it NVND CNTS would level men's wits and leave little scope for that inborn capacity which is called genius. As a matter of fact Bacon's via has proved hopelessly impracticable, while the anticipation of nature by the invention of hypotheses based on incomplete inductions which he specifically condemns has proved itself to be a most efficient indeed an indispensable instrument of scientific progress. Finally that transcendental alchemy the super inducement of new forms on matter which Bacon declares to be the supreme aim of science has been wholly ignored by those who have created the physical knowledge of the present day. Even the eloquent advocacy of the chancellor brought no unmixed good to physical science. It was natural enough that the man who in his better moments took all knowledge for his patrimony but in his worse sold that birthright for the mess of potage of court favor and professional success for pomp and show should be led to attach an undue value to the practical advantages which he foresaw as Roger Bacon and indeed Seneca had foreseen long before his time must follow in the train of the advancement of natural knowledge. The burden of Bacon's pleadings for science is the gathering of fruit, the importance of winning solid material advantages by the investigation of nature and the desirableness of limiting the application of scientific methods of inquiry to that field. Bacon's younger contemporary Hobbes casting aside the prudent reserve of his predecessor in regard to those matters about which the crown or the church might have something to say extended scientific methods of inquiry to the phenomena of mind and the problems of social organization while at the same time he indicated the boundary between the province of real and that of imaginary knowledge. The principles of philosophy and the Leviathan embody a coherent system of purely scientific thought in language which is a model of clear and vigorous English style. At the same time in France a man of far greater scientific capacity than either Bacon or Hobbes, Rene Descartes, not only in his immortal discord de la method and elsewhere went down to the foundations of scientific certainty but in his princete de philosophie indicated where the goal of physical science really lay. However Descartes was an eminent mathematician and it would seem that the bent of his mind led him to overestimate the value of deductive reasoning from general principles as much as Bacon had underestimated it. The progress of physical science has been affected neither by Baconians nor by Cartesians as such but by men like Galileo and Harvey Boyle and Newton who would have done their work just as well if neither Bacon nor Descartes had ever propounded their views respecting the manner in which scientific investigation should be pursued. The progress of science during the first century after Bacon's death by means verified his sanguine prediction of the fruits which it would yield. Four though the revived and renewed study of nature had spread and grown to an extent which surpassed reasonable expectation the practical results the good to men's estate where at first by no means apparent. Sixty years after Bacon's death Newton had crowned the long labors of the astronomers and the physicist by coordinating the phenomena of solar motion throughout the visible universe into one vast system but the principia helped no man to either wealth or comfort. Descartes, Newton and Leibniz had opened up new worlds to the mathematician but the acquisitions of their genius enriched only man's ideal estate. Descartes had laid the foundations of rational cosmogony and of physiological psychology. Boyle had produced models of experimentation in various branches of physics and chemistry. Pascal and Torricelli had weighed the air. Malpighi and Gru, Ray and Willoughby had done work of no less importance in the biological sciences but weaving and spinning were carried on with the old appliances. Nobody could travel faster by sea or by land than at any previous time in the world's history and King George could send a message from London to York no faster than King John might have done. Metals were worked from their oars by immemorial rule of thumb and the centre of the iron trade of these islands was still among the oak forests of Sussex. The utmost skill of our mechanitions did not get beyond the production of a coarse watch. The middle of the 18th century is illustrated by a host of great names in science English, French, German and Italian especially in the fields of chemistry, geology and biology but this deepening and broadening of natural knowledge produced next to no immediate practical benefits. Even if at this time Francis Bacon could have returned to the scene of his greatness and of his littleness he must have regarded the philosophic world which praised and disregarded his precepts with great disfavor. If ghosts are consistent he would have said these people are all wasting their time just as Gilbert and Kepler and Galileo and my worthy physician Harvey did in my day. Where are the fruits of the restoration of science which I promised? This accumulation of bare knowledge is all very well but quiabono. Not one of these people is doing what I told him to do and seeking that secret of the cause of forms which will enable men to deal at will with matter and super induce new natures upon old foundations. But a little later that growth of knowledge beyond imaginable utilitarian ends which is the condition precedent of its practical utility began to produce some effect upon practical life and the operation of that part of nature we call human beings began to create not new natures in bacon sense but a new nature the existence of which is dependent upon men's efforts which is subservient to their wants and which would disappear if man's shaping and guiding hand were withdrawn. Every mechanical artifice every chemically pure substance employed in manufacture every abnormally fertile race of plants or rapidly growing plants is part of the new nature created by science without it the most densely populated regions of modern Europe and America must retain their primitive sparsely inhabited agricultural or pastoral condition it is the foundation of our wealth and the condition of our safety from submergence by another flood of barbarous hordes it is the bond which unites into a solid political whole it secures us from the recurrence of the pestilences and famines of former times it is the source of endless comforts and conveniences which are not mere luxuries but conduced to physical and moral well-being during the last 50 years this new birth of time this new nature be gotten by science upon fact has pressed itself daily and hourly upon our attention and has worked miracles which have provided the whole fashion of our lives what wonder then if these astonishing fruits of the tree of knowledge are too often regarded by both friends and enemies as the be all and end all of science what wonder if some eulogize and others revile the new philosophy for its utilitarian ends and its merely material triumphs in truth the new philosophy deserves neither the praise of its eulogists nor the blame of its slanderers as I have pointed out its disciples were guided by no search after practical fruits during the great period of its growth and it reached adolescence without being stimulated by any rewards of that nature the bear enumeration of the names of the men who were the great lights of science in the latter part of the 18th and the first decade of the 19th century of Herschel of Laplace of Young of Fresnel of Orsted of Cavendish of Lavossier of Davie of Lamarck of Cuvier of Jussieu of Dickendall of Werner and of Hutton suffices to indicate the strength of physical science in the age immediately preceding that of which I have to treat but of which of these great men can it be said that their labors were directed to practical ends I do not call to mind even an invention of practical utility which we owe to any of them except the safety lamp of Davie Werner certainly paid attention to mining and I have not forgotten James Watt but though some of the most important of the improvements by which Watt converted the steam engine invented long before his time into the obedient slave of man were suggested and guided by his acquaintance with scientific principles his skill as a practical mechanition and the efficiency of Bolton's workmen had quite as much to do with the realization of his projects in fact the history of physical science teaches and we cannot too carefully take the lesson to heart that the practical advantages attainable through its agency never have been and never will be sufficiently attractive to men inspired by the inborn genius of the interpreter of nature to give them courage to undergo the toils and make the sacrifices which that calling requires from its votaries that which stirs their pulses is the love of knowledge and the joy of the discovery of the causes of things sung by the old poets the supreme delight of extending the realm of law and order ever farther towards the unattainable goals of the infinitely great and the infinitely small between which our little race of life is run in the course of this work the physical philosopher sometimes intentionally much more often unintentionally lights upon something which proves to be of practical value great is the rejoicing of those who are benefited thereby and for the moment science is the Diana of all the craftsmen but even while the cries of jubilation resound and this flotsam and jetsam of the tide of investigation is being turned into the wages of workmen and the wealth of capitalists the crest of the wave of scientific investigation is far away on its course over the illimitable ocean of the unknown far be it for me to depreciate the value of the gifts of science to practical life or to cast a doubt upon the propriety of the course of action of those who follow science in the hope of finding wealth alongside truth or even wealth alone such a profession is as respectable as any other and quite as little do I desire to ignore the fact that if industry owes a heavy debt to science it has largely repaid the loan by the important aid which it has in its turn rendered to the advancement of science in considering the causes which hindered the progress of physical knowledge in the schools of Athens and of Alexandria it has often struck me that where the Greeks did wonders was in just those branches of science such as geometry astronomy and anatomy which are susceptible a very considerable development of any or any but the simplest appliances it is a curious speculation to think what would have become of modern physical science if glass and alcohol had not been easily obtainable and if the gradual perfection of mechanical skill for industrial ends had not enabled investigators to obtain at comparatively little cost microscopes telescopes and all the exquisitely delicate apparatus for determining weight and measure and for estimating the lapse of time with exactness which they now command if science has rendered the colossal development of modern industry possible beyond a doubt industry has done no less for modern physics and chemistry and for a great deal of modern biology and as captains of industries have at last begun to be aware that the condition of success in that warfare under the terms of peace which is known as industrial competition lies in the discipline of the troops and the use of arms of precision just as much as it does in the warfare which is called war their demand for that discipline which is technical education is reacting upon science in a manner which will assuredly stimulate its future growth to an incalculable extent it has become obvious that the interest of science and of industry are identical that science cannot make a step forward without sooner or later with new channels for industry and on the other hand that every advance of industry facilitates those experimental investigations upon which the growth of science depends we may hope that at last the weary misunderstanding between the practical men who profess to despise science and the high and dry philosophers who profess to despise practical results is at an end nevertheless that which is true of the infancy of physical science in the Greek world that which is true of its adolescence in the 17th and 18th centuries remains true of its ripe age in these latter days of the 19th century the great steps in its progress have been made, are made and will be made by men who seek knowledge simply because they crave for it they have their weaknesses their follies, their vanities and their rivalries like the rest of the world that impede their usefulness this chief end redeems them Fresnel, after a brilliant career of discovery in some of the most difficult regions of physical mathematical science died at 39 years of age the following passage of a letter from him to Young written in November 1824 quoted by Weewel so aptly illustrates the spirit which animates the scientific inquirer that I may cite it for a long time that sensibility or that vanity which people call love of glory is much blunted in me I labor much less to catch the suffrages of the public than to obtain an inward approval which has always been the mental reward of my efforts without doubt I have often wanted the spur of vanity to excite me to pursue my researches in moments of disgust and discouragement but all the compliments which I have received from M. M. Arago Dilaplas or Bayat never gave me so much pleasure as the discovery of a theoretical truth or the confirmation of a calculation by experiment nothing great in science has ever been done by men whatever their powers in whom the divine a flattest of the truth seeker was wanting men of moderate capacity have done great things because it animated them and men of great natural gifts have failed absolutely or relatively because they lack this one thing needful to anyone who knows the business of investigation practically Bacon's notion of establishing a company of investigators to work for fruits as if the pursuit of knowledge were a kind of mining operation and only required well-directed picks and shovels seems very strange memorable example of the research that was applied to the discovery of new truths this is one of the most distinguished of living French savants of the corporate chemical work of the old Académie des Sciences in science as an art and as I believe in every other sphere of human activity there may be wisdom in a multitude of counselors but it is only in one or two of them and in scientific inquiry at any rate it is to that one or two that we must look for light and guidance Newton said that he made his discoveries by intending his mind on the subject no doubt truly but to equal his success one must have the mind which he intended forty lesser men might have intended their minds till they cracked without any like result it would be idle either to affirm or to deny that the last half century has produced men of science of the caliber of Newton it is sufficient that it can show a few capacities of the first rank competent not only to deal profitably with the inheritance bequeathed by their scientific forefathers but to pass on to their successors physical truths of a higher order than any yet reached by the human race and if they have succeeded as Newton succeeded it is because they have sought truth as he sought it with no other object than the finding it I am conscious that in undertaking to give even the briefest sketch of the progress of physical science in all its branches during the last half century I may be thought to have exhibited more courage than discretion and perhaps more presumption than either so far as physical science is concerned the days of admirable critons have long been over and the most indefagable of hard workers may think he has done well if he has mastered one of its minor subdivisions nevertheless it is possible for anyone who has familiarized himself with the operations of science in one department to comprehend the significance and even to form a general estimate of the value of the achievements of specialists in other departments nor is there any lack either of guidance or of aids to ignorance by a happy chance the first edition of Weywell's History of Inductive Sciences was published in 1837 and it affords a very useful view of the state of things at the commencement of the Victorian Epic as to subsequent events there are numerous excellent summaries of the progress of various branches of science especially up to 1881 which was the jubilee year of the British Association and with respect to the biological sciences with some parts of which my studies have familiarized me my personal experience nearly coincides with the preceding half century I may hope therefore that my chance of escaping serious errors is as good as that of anyone else who might have been persuaded to undertake the somewhat perilous enterprise in which I find myself engaged there is yet another prefatory remark which it seems desirable I should make it is that I think it proper to confine myself to the work done without saying anything about the doers of it meddling with questions of merit and priority is a thorny business at the best of times and unless in case of necessity altogether undesirable when one is dealing with contemporaries no such necessity lies upon me and I shall therefore mention no names of living men lest, perchance, I should incur the reproof which the Israelites who struggled with one another in the field addressed to Moses who made thee a prince and a judge over us physical science is one and indivisible although for practical purposes it is convenient to mark it out into the primary regions of physics chemistry and biology and to subdivide these into subordinate provinces yet the method of investigation and the ultimate object of the physical inquirer are everywhere the same the object is the discovery of the rational order which pervades the universe the method consists of observation and experiment which is observation under artificial conditions for the determination of the facts of nature of inductive and deductive reasoning for the discovery of their mutual relations and connection the various branches of physical science differ in the extent to which at any given moment of their history observation on the one hand or radiosination on the other is their more obvious feature but in no other way and nothing can be more incorrect than the assumption one sometimes meets with that physics has one method chemistry another and biology a third all physical science starts from certain postulates one of them is the objective existence of a material world it is assumed that the phenomena which are comprehended under this name have a substratum of extended impenetrable mobile substance which exhibits the quality known as inertia and is termed matter I am aware that this proposition may be challenged it may be said for example that on the hypothesis of Boskovich matter has no extension being reduced to mathematical points serving as centers of forces but as the forces of the various centers are conceived to limit one another's action in such a manner that an area around each center has an individuality of its own extension comes back in the form of that area again a very eminent mathematician and physicist the late clerk Maxwell has declared that impenetrability is not essential to our notions of matter and that two atoms may conceivably occupy the same space I am loath to dispute any dictum of a philosopher as remarkable for the subtlety of his intellect as for his vast knowledge but the assertion that one in the same point or area of space can have different conceivably opposite attributes appears to me to violate the principle of contradiction which is the foundation not only of physical science but of logic in general it means that A cannot be not A another postulate is the universality of the law of causation that nothing happens without a cause that is a necessary precedent condition and that the state of the physical universe at any given moment is the consequence of its state at any preceding moment another is that any of the rules or so-called laws of nature by which the relation of phenomena is truly defined is true for all time the validity of these postulates is a problem of metaphysics they are neither self-evident nor are they strictly speaking demonstrable the justification of their employment as axioms of physical philosophy lies in the circumstance that expectations logically based upon them are verified or at any rate not contradicted whenever they can be tested by experience physical science therefore rests unverified or uncontradicted hypotheses being the case it is not surprising that a great condition of its progress has been the invention of verifiable hypotheses it is a favorite popular delusion that the scientific inquirer is under a sort of moral obligation to abstain from going beyond that generalization of observed facts which is absurdly called baconian induction but anyone who is practically acquainted with scientific work is aware that those who refuse to go beyond fact rarely get as far as fact and anyone who has studied the history of science knows that almost every great step therein has been made by the anticipation of nature that is by the invention of hypotheses which though verifiable often had very little foundation to start with and not infrequently in spite of a long career of usefulness turned out to be wholly erroneous in the long run the geocentric system of astronomy with its eccentrics and its epicycles was an hypothesis utterly at variance with fact which nevertheless did great things for the advancement of astronomical knowledge Kepler was the wildest of guessers Newton's corpuscular theory of light was of much temporary use in optics though nobody now believes in it and the undilatory theory which has superseded the corpuscular theory and has proved one of the most fertile of instruments of research is based on the hypothesis of the existence of an aether the properties of which are defined in propositions some of which to ordinary apprehension seem physical antimonies it sounds paradoxical to say that the attainment of scientific truth has been effected to a great extent by the help of scientific errors but the subject matter of physical science is furnished by observation which cannot extend beyond the limits of our faculties while even within those limits we cannot be certain that any observation is absolutely exact and exhaustive hence it follows that any given generalization from observation may be true within the limits of our powers of observation at a given time and yet turn out to be untrue when those powers of observation are directly or indirectly enlarged or to put the matter in another way a doctrine which is untrue absolutely may to a very great extent be susceptible of an interpretation in accordance with the truth at a certain period in the history of astronomical science the assumption that the planets move in circles was true enough to serve the purpose of correlating such observations as were then possible after Kepler the assumption that they move in ellipses became true enough in regard to the state of observational astronomy at that time we say still that the orbits of the planets are ellipses because for all ordinary purposes that is a sufficiently near approximation to the truth but as a matter of fact the center of gravity of a planet describes neither an ellipse or any other simple curve but an immensely complicated undulating line it may fairly be doubted whether any generalization or hypothesis based upon physical data is absolutely true in the sense that a mathematical proposition is so but if its errors can become apparent only outside the limits of practicable observation it may be just as usefully adopted for one of the symbols of that algebra by which we interpret nature as if it were absolutely true end of section 1 this has been a LibriVox recording all LibriVox recordings are in the public domain section 2 of the advance of science in the last half century by T.H. Huxley the development of every branch of physical knowledge presents three stages which in their logical relation are successive the first is the determination of the sensible character and order of the phenomena this is natural history in the original sense of the term and here nothing but observation and experiment avail us the second is the determination of the constant relations of the phenomena thus defined and their expressions in rules or laws the third is the explication of these particular laws by deduction from the most general laws of matter and motion the last two stages constitute natural philosophy in its original sense in this region the invention of verifiable hypotheses is not only permissible but is one of the conditions of progress historically no branch of science has followed this order of growth but from the dawn of exact knowledge to the present day observation experiment and speculation have gone hand in hand and whenever science has halted or strayed from the right path it has been either because its votaries have been content with the mere unverified or unverifiable speculation and this is the commonest case because observation and experiment are hard work while speculation is amusing or it has been because the accumulation of details of observation has for a time excluded speculation the progress of physical science since the revival of learning is largely due to the fact that men have gradually learned to lay aside the consideration of unverifiable hypotheses to guide observation and experiment by verifiable hypotheses and to consider the latter not as ideal truths the real entities of an intelligible world behind phenomena is a symbolic language by the aid of which nature can be interpreted in terms apprehensible by our intellect and if physical science during the last 50 years has attained dimensions beyond all former precedents and can exhibit achievements of greater importance than any former such period can show it is because able men animated by the true scientific spirit carefully trained in the method of science and having at their disposal immensely improved appliances have devoted themselves to the enlargement of the boundaries of natural knowledge in greater number than during any previous half century of the world's history I have said that our epic can produce achievements in physical science of greater moment that any other has to show, advisedly and I think that there are three great products of our time which justify the assertion one of these is that doctrine concerning the constitution of matter which for want of a better name I will call molecular the second is the doctrine of conservation of energy the third is the doctrine of evolution each of these was foreshadowed more or less distinctly in former periods of the history of science and so far is either from being the outcome of purely inductive reasoning that it would be hard to overrate the influence of metaphysical and even of theological considerations upon the development of all three the peculiar merit of our epic is that it has shown how these hypotheses connect a vast number of seemingly independent partial generalizations that it has given them that precision of expression which is necessary for their exact verification and that it has practically proved their value as guides to the discovery of new truth all three doctrines are intimately connected and each is applicable to the whole physical cosmos but as might have been expected from the nature of the case the first two grew mainly out of the consideration of physical chemical phenomena while the third in great measure owes its rehabilitation if not its origin to the study of biological phenomena in the early decades of this century a number of important truths applicable in part to matter in general and in part to particular forms of matter had been ascertained by the synthesis and chemists the laws of motion of visible and tangible or molar matter had been worked out to a great degree of refinement and embodied in the branches of science known as mechanics hydrostatics and pneumatics these laws had been shown to hold good so far as they could be checked by observation and experiment throughout the universe on the assumption that all such masses of matter possessed inertia and were susceptible of acquiring motion in two ways firstly by impact or impulse from without and secondly by the operation of certain hypothetical causes of motion termed forces which were usually supposed to be resident in the particles of the masses themselves and to operate at a distance in such a way as to tend to draw any two such masses together or to separate them more widely with respect to the ultimate constitution of these masses the same two antagonistic opinions which had existed since the time of Democritus and of Aristotle were still face to face according to one matter was discontinuous and consisted of minute indivisible particles or atoms separated by a universal vacuum according to the other it was continuous and the finest distinguishable or imaginable particles were scattered through the attenuated general substance of the plenum a rough analogy to the latter case would be afforded by granules of ice diffused through water to the former such granules diffused through absolutely empty space in the latter part of the 18th century the chemist had arrived at several very important generalizations respecting those properties of matter with which they were especially concerned however plainly ponderable matter seem to be originated and destroyed in their operations they prove that as mass or body it remained indestructible and ingenerable and that so far it varied only in its perceptibility by our senses the course of investigation further proved that a certain number of the chemically separable kinds of matter were unalterable by any known means except in so far as they might be made to change their state from solid to fluid or vice versa unless they were brought into contact with other kinds of matter and that the properties of these matter were always the same whatever their origin all other bodies were found to consist of two or more of these which thus took the place of the four elements of the ancient philosophers further it was proved that in forming chemical compounds bodies always unite in a definite proportion by weight or in simple multiples of that proportion and that if any one body were taken as a standard every other could have a number as its proportional combining weight it was on this foundation of fact that Dalton based his re-establishment of the old atomic hypothesis on a new empirical foundation it is obvious that if elementary matter consists of indestructible and indivisible particles each of which constantly preserves the same weight relatively to all the others compounds formed by the aggregation of two, three, four or more such particles must exemplify the rule of combination in definite proportions deduced from observation in the meanwhile the gradual reception of the undulatory theory of light necessitated the assumption of the existence of an ether filling all space but whether this ether was to be regarded as a strictly material and continuous substance was an undecided point and hence the revived atomism escaped strangling in its birth for it is clear that if the ether is admitted to be a continuous material substance democratic atomism is at an end and Cartesian continuity takes its place the real value of the new atomic hypothesis however did not lie in the two points which democratis and his followers would have considered essential namely the indivisibility of the atoms and the presence of an inter-atomic vacuum but in the assumption that to the extent to which our means of analysis take us material bodies consist of definite minute masses each of which so far as physical and chemical processes of division go may be regarded as a unit having a practically permanent individuality just as a man is the unit of sociology without reference to the actual fact of his divisibility so such a minute mass is the unit of physical chemical science that smallest material particle after any given circumstances acts as a whole molecule would be the more appropriate name for such a particle unfortunately chemists employ this term in a special sense as a name for an aggregation of their smallest particles for which they retain the designation of atoms the doctrine of specific heat originated in the 18th century it means that the same mass of a body under the same circumstances always requires the same quantity to raise it to a given temperature but that equal masses of different bodies require different quantities ultimately it was found that the quantities of heat required to raise equal masses of the more perfect gases through equal ranges of temperature were inversely proportional to their combining weights thus a definite relation was established between the hypothetical units and heat the phenomena of electrolytic decomposition showed that there was a like-close relation between these units and electricity the quantity of electricity generated by the combination of any two units is sufficient to separate any other two which are susceptible of such decomposition the phenomena of isomorphism showed a relation between the units and crystalline forms certain units are thus able to replace others in a crystalline body without altering its form and others are not again the laws of the effect of pressure and heat on gaseous bodies the fact that they combine indefinite proportions by volume and that such proportion bears a simple relation to their combining weights all harmonized with a Daltonian hypothesis and led to the bold speculation known as the law of Avogadro that all gaseous bodies under the same physical conditions contain the same number of units in the form in which it was first enunciated this hypothesis was incorrect perhaps it is not exactly true in any form but it is hardly too much to say that chemistry and molecular physics would never have advanced to their present condition unless it had been assumed to be true another immense service rendered by Dalton as a corollary of the new atomic doctrine was the creation of a system of symbolic notation that made the nature of chemical compounds and processes easily intelligible and easy of recollection but by its very form suggested new lines of inquiry the atomic notation was as serviceable to chemistry as the binomial nomenclature and the classificatory schematism of Linnaeus were to zoology and botany side by side with these advances arose in another which also has a close parallel of biological science if the unit of a compound is made up by the aggregation of elementary units the notion that these must have some sort of definite arrangement inevitably suggest itself and such phenomena as double decomposition pointed not only to the existence of a molecular architecture but to the possibility of modifying a molecular fabric without destroying it by taking out some of the component units and replacing them by others the class of neutral salts for example includes a great number of bodies in many ways similar in which the basic molecules or the acid molecules may be replaced by other basic and other acid molecules without altering the neutrality of the salt just as a cube of bricks remains a cube so long as any brick that is taken out is replaced by another of the same shape and dimensions whatever its weight or other properties may be facts of this kind give rise to the conception of types of molecular structure just as the recognition of the unity and diversity of the structure of the species of plants and animals gave rise to the notion of biological types the notation of chemistry enabled these ideas to be represented with precision and they acquired an immense importance when the improvement of methods of analysis which took place about the beginning of our period enabled the composition of the so cold organic bodies to be determined with rapidity and precision at present more organic analyses are made in a single day than were accomplished before libix time in a whole year a large proportion of these compounds contain not more than three or four elements of which carbon is the chief but their number is very great and the diversity of their physical and chemical properties is astonishing the ascertainment of the proportion of each element in these compounds affords little or no help towards accounting for their diversities widely different bodies being often very similar or even identical in that respect and in the last case that of isomeric compounds the appeal to diversity of arrangement of the identical component units was the only obvious way out of the difficulty here again hypothesis proved to be of great value not only was the search for evidence of diversity of molecular structure successful but the study of the process of taking two pieces led to the discovery of the way to put together and vast numbers of compounds some of them previously known only as products of the living economy have thus been artificially constructed chemical work at the present day is to a large extent synthetic or creative that is to say the chemist determines theoretically that certain non-existent compounds ought to be available and he proceeds to produce them it is largely because the chemical theory and practice of our epic have passed into this deductive and synthetic stage that they are entitled to the name of the new chemistry which they commonly receive but this new chemistry has grown up by the help of hypothesis such as those of Dalton and of Avogadro and that the singular conception of bonds invented to collocate the facts of valency or atomicity the first of time to make its way while the second fell into oblivion for many years after it was propounded for lack of empirical justification as for the third it may be doubted if anyone regards it as more than a temporary contrivance but some of these hypotheses have done yet further service combining them with the mechanical theory of heat and the doctrine of the conservation of energy which are also products of our time arrived at an entirely new conception of the nature of gaseous bodies and of the relation of the physical chemical units of matter to the different forms of energy the conduct of gases under varying pressure and temperature their diffusability their relation to radiant heat and to light the evolution of heat when bodies combine the absorption of heat when they are dissociated and a host of other molecular phenomena have been shown to be deducible to chemical and statical principles which apply to molar motion and rest and the tendency of physical chemical science is clearly towards the reduction of the problems of the world of the infinitely little as it already has reduced those of the infinitely great world to questions of mechanics in the meantime the primitive atomic theory which has served as the scaffolding for the edifice of modern physics and chemistry has been quietly dismissed I cannot discover that any contemporary physicist or chemist believes in the real indivisibility of atoms or in an interatomic matterless vacuum. Atoms appear to be used as mere names for physical chemical units which have not yet been subdivided and molecules for physical chemical units which are aggregates of the former and these individualized particles are supposed to move in an endless ocean of a vastly more subtle matter the ether if this ether is a continuous substance therefore we have got back from the hypothesis of Dalton to that of Descartes but there is much reason to believe that science is going to make a still further journey and inform if not altogether in substance to return to the point of view of Aristotle. The greater number of the so-called elementary bodies now known had been discovered before the commencement of our epic and it had become apparent that they were by no means truly similar or dissimilar but that some of them at any rate constituted groups the several members of which were as much like one another as they were unlike the rest chlorine, iodine, bromine and fluorine thus formed a very distinct group sulfur and selenium another boron and silicon another potassium sodium and lithium another and so on. In some cases the atomic weights of such allied bodies were nearly the same and could be arranged in series with like differences between the several terms. In fact the elements afforded indications that they were susceptible of a classification in natural groups such as those into which animals and plants fall. Recently this subject has been taken up afresh with a result which may be stated roughly in the following terms. If the 65 or 68 recognized elements are arranged in the order of their atomic weights from hydrogen the lightest as unity to uranium the heaviest as 240 the series does not exhibit one continuous progressive modification in the physical and chemical characters of its several terms but breaks up into a number of sections in each of which the several terms present analogies with the corresponding terms of the other series. Thus the whole series does not run A, B, D, E, F, G, H, I, K, etc. but A, B, C, D A, B, C, D alpha, beta, gamma, delta etc. So that it is said to express a periodic law of recurrent similarities. Or the relation may be expressed in another way. In each section of the series the atomic weight is greater than in the preceding section so that if W is the atomic weight of any element in the first segment W plus X will represent the atomic weight of any element in the next and W plus X plus Y the atomic weight of any element in the next and so on. Therefore the sections may be represented as parallel series the corresponding terms of which have analogous properties Each successive series starting with a body the atomic weight of which is greater than that of any in the in the following fashion column 1 D, C, B, A W column 2 D, C, B, A W plus X column 3 delta, gamma, beta, alpha W plus X plus Y This is the conception with which biologists are very familiar animal implant groups constantly appearing as series of parallel modifications of similar and yet different primary forms In the living world, facts of this kind are now understood to mean evolution from a common prototype It is difficult to imagine that in the not living world they are devoid of significance Is it not possible, nay probable that they may mean the evolution of our elements from a primary undifferentiated form of matter 50 years ago such a suggestion would have been scouted as a revival of the dreams of the alchemists At present it may be said to be the burning question of physical chemical science In fact, the so called vortex ring hypothesis is a very serious and remarkable attempt to deal with material units from a point of view which is consistent with the doctrine of evolution It supposes the ether to be a uniform substance and that the elementary units are, broadly speaking, permanent whirlpools or vortices of this ether, the properties of which depend on their actual and potential modes of motion It is curious and highly interesting to remark that this hypothesis reminds us not only of the speculations of Descartes, but of those of Aristotle The resemblance of the vortex rings to the tourbillons of Descartes is little more than nominal but the correspondence between the relative notion of a distinction between primary and derivative matter is, to a certain extent, real For this ethereal earth stuff of the modern corresponds very closely with the perhotile of Aristotle and the materia prima of his medieval followers While matter differentiated into our elements is the equivalent of the first stage of progress towards the hecheitile, or finished matter of the ancient philosophy If the material units of the existing order of nature are specialized portions of a relatively homogeneous materia prima which were originated under conditions that have long ceased to exist and which remained unchanged and unchangeable under all conditions whether natural or artificial hitherto known to us It follows that the speculation that they may be indefinitely altered or that new units may be generated under conditions yet to be discovered is perfectly legitimate Theoretically at any rate the transmutability of the elements is a verifiable scientific hypothesis and such inquiries as those which have been set afoot into the possible dissociative action of the great heat of the sun upon our elements are not only legitimate but are likely to yield results which, whether affirmative or negative will be of great importance The idea that atoms are absolutely in generable and immutable in the manufactured articles stands on the same sort of foundation as the idea that biological species are manufactured articles stood 30 years ago and the supposed constancy of the elementary atoms during the enormous lapse of time measured by the existence of our universe is of no more weight against the possibility of change in them in the infinity of antecedent time than the constancy of species in Egypt since the days of Ramses is evidence of their immutability during all past epics of the Earth's history It seems safe to prophesy that the hypothesis of the evolution of the elements from a primitive matter will in future play no less apart in the history of science than the atomic hypothesis which, to begin with had no greater if so great an empirical foundation It may perhaps occur to the reader that the boasted progress of physical science does not come too much The present conceptions of the fundamental nature of matter are expressible in terms employed more than 2000 years ago by the old master of those that know Such a criticism, however, would involve forgetfulness of the fact that the connotation of these terms in the mind of the modern is almost infinitely different from that which they possessed in the mind of the ancient philosopher In antiquity they meant little more than vague speculation In the present day they indicate definite physical conceptions, susceptible of mathematical treatment and giving rise to innumerable deductions the value of which can be experimentally tested The old notions produced little more than floods of dialectics The new are powerful aids towards the increase of solid knowledge Every day observation shows that of the bodies which compose the material world some are in motion and some are appear to be at rest Of the bodies in motion some, like the sun and stars exhibit a constant movement regular in amount and direction for which no external cause appears Others, as stones and smoke seem also to move of themselves when external impediments are taken away But these appear to tend to move in opposite directions The bodies we call heavy such as stones downwards and the bodies we call light such as smoke and steam upwards And as we further notice that the earth below our feet is made up of heavy matter while the air above our heads is extremely light matter it is easy to regard this fact as evidence that the lower region is the place to which heavy things tend their proper place in short while the upper region is the proper place of light things And to generalize the facts observed by saying that bodies are the proper places All these seem to be natural motions dependent on the inherent faculties or tendencies of bodies themselves But there are other motions which are artificial or violent as when a stone is thrown from the hand or is knocked by another stone in motion In such cases as these for example when a stone is cast from the hand the distance traveled by the stone appears to depend partly on its weight and partly upon the exertion of the thrower So that the weight of the stone remaining the same it looks as if the mode of power communicated to it were measured by the distance to which the stone travels as if in other words the power needed to send it a hundred yards was twice as great as that needed to send it fifty yards These apparently obvious conclusions from the everyday appearances of rest and motion fairly represent the state of opinion upon the subject which prevailed in ancient Greeks and remained a dominant until the age of Galileo The publication of the Principia of Newton in 1686 and 7 marks the epic at which the progress of mechanical physics had affected a complete revolution of thought on these subjects By this time it had been made clear that the old generalizations were either incomplete or totally erroneous that a body once set in motion will continue to move in a straight line of inconceivable time or distance unless it is interfered with that any change of motion is proportional to the force which causes it and takes place in the direction in which that force is exerted and that when a body in motion acts as a cause of motion on another the latter gains as much as the former loses and vice versa It is to be noted however that while in contradistinction to the ancient idea of the inherent tendency to motion of bodies the absence of any such spontaneous power of motion was accepted as a physical axiom by the moderns the old conception virtually maintained itself in a new shape For in spite of Newton's well known warning against the absurdity of supposing that one body can act on another at a distance through a vacuum the ultimate particles of matter were generally assumed to be the seats of perennial causes of motion termed attractive and repulsive forces in virtue of which any two such particles without any external impression of motion or intermediate material agent were supposed to tend to approach or remove from one another and this view of the duality of the causes of motion is very widely held at the present day Another important result of investigation attained in the 17th century was the proof and quantitative estimation of physical inertia in the old philosophy a curious conjunction of ethical and physical prejudices had led to the notion that there was something ethically bad and physically obstructive about matter Aristotle attributes all irregularities in apparent distiliologies in nature to the disobedience or sluggish yielding of matter to the shaping and guiding influence of those reasons and causes which were hypothesized in his ideal forms In modern science the conception of inertia or the resistance to change of matter is complex In part it contains a corollary from the law of causation a body cannot change its state in respect of rest or motion without a sufficient cause but in part it contains generalizations from experience One of these is that there is no such sufficient cause resident in any body and that therefore it will rest or continue in motion as no external cause of change acts upon it The other is that the effect which the impact of a body in motion produces upon the body on which it impinges depends other things being alike on the relation of a certain quality of each which is called mass Given a cause of motion of a certain value the amount of motion measured by distance traveled in a certain time which it will produce in a given quantity of matter say a cubic inch is not always the same but depends on what that matter is a cubic inch of iron will go faster than a cubic inch of gold hence it appears that since equal amounts of motion have X hypothesis been produced the amount of motion in a body does not depend on its speed alone but on some property of the body To this the name of mass has been given and since it seems reasonable to suppose quantity of matter moving slowly possesses as much motion as a small quantity moving faster mass has been held to express quantity of matter It is further demonstrable that at any given time in place the relative mass of any two bodies is expressed by the ratio of their weights When all of these great truths respecting molar motion or the movements of visible and tangible masses had been shown to hold good not only of terrestrial bodies but of all those which constitute the visible universe and the movements of the macrocosm had thus been expressed by a general mechanical theory there remained a vast number of phenomena such as those of light, heat electricity, magnetism and those of the physical and chemical changes which do not involve molar motion Newton's corpuscular theory of light was an attempt to deal with one great theory of these phenomena on mechanical principles and it maintained its ground until at the beginning of the 19th century the undulatory theory proved itself to be a much better working hypothesis heat up to that time and indeed much later was regarded as an imponderable substance, caloric as a thing which was absorbed by bodies when they were warmed and was given out as they cooled and which moreover was capable of entering into a sort of chemical system and so becoming latent Rumford and Davey had given a great blow to this view of heat by proving that the quantity of heat which two portions of the same body could be made to give out by rubbing them together was practically illimitable. This result brought philosophers face to face with the contradiction of supposing that a finite body could contain an infinite quantity of another body but it was not until 1843 that clear and unquestionable experimental proof was given of the fact that there is a definite relation between mechanical work and heat that so much work always gives rise under the same conditions to so much heat and so much heat to so much mechanical work thus originated the mechanical theory of heat which became the starting point of the modern doctrine of the conservation of energy molar motion had appeared to be destroyed by friction it was proved that no destruction took place but that an exact equivalent of the energy of the lost molar motion appears as that of the molecular motion or motion of the smallest particles of a body which constitutes heat the loss of the masses is the gain of their particles before 1843 however the doctrine of conservation of energy had been approached Bacon's chief contribution to positive science is the happy guess for the context shows that it was little more that heat may be a mode of motion Descartes affirmed the quantity of motion in the world to be constant Newton nearly gave expression to the complete theorem while Rumford's and Davies experiments suggested though they did not prove the equivalency of mechanical and thermal energy again the discovery of voltaic electricity and the marvelous development of knowledge in that field effected by such men as Davey Faraday Orsted, Ampere and Maloney had brought to light a number of facts which tended to show that the so-called forces at work in light, heat, electricity and magnetism in chemical and in mechanical operations were intimately and in various cases quantitatively related it was demonstrated that anyone could be obtained at the expense of any other an apparatus was devised which exhibited the evolution of all these evidence of action from one source of energy hence the idea of the correlation of forces which was the immediate forerunner of the doctrine of the conservation of energy it is a remarkable evidence of the greatness of the progress in this direction which has been affected in our time that even the second edition of the history of the inductive sciences which was published in 1846 contains no illusion either to the general view of the correlation of forces published in England in 1842 or to the publication in 1843 of the first of the series of experiments by which the mechanical equivalent of heat was correctly ascertained this is the more curious as Ampere's hypothesis that vibrations of molecules causing and caused by vibrations of the ether constitute heat is discussed we will remarks apropos of Bacon's definition of heat that it is an expansive restrained motion modified in certain ways and exerted in the smaller particles of the body that although the exact nature of heat is still an obscure and controversial matter the science of heat now consists of many important truths and that to none of these truths is there any approximation in Bacon's essay in point of fact Bacon's statement however much open to criticism does contain a distinct approximation to the most important of all the truths respecting heat which had been discovered when we will wrote such a failure on the part of a contemporary of great requirements and remarkable intellectual powers to read the science of the times is a lesson any warning worthy of being deeply pondered by anyone who attempts to prognosticate the course of scientific progress and of section two this is a LibriVox recording all LibriVox recordings are in the public domain section three of the advance of science in the last half century by T. H. Huxley 1889 I have pointed out that the growth of clear and definite views respecting the constitution of matter has led to the conclusion that so far as natural agencies are concerned it is in generable and indestructible in so far as matter may be conceived to exist in a purely passive state it is imaginably older than motion but as it must be assumed to be susceptible of motion a particle of bare matter at rest must be endowed with the potentiality of motion such a particle however by the supposition can have no energy for there is no cause why it should move suppose now that it receives an impulse it will begin to move with a velocity inversely proportional to its mass on the one hand and directly proportional to the strength of the impulse on the other and will possess kinetic energy in virtue of which it will not only continue to move forever if unimpeded but if it impinges on another such particle it will impart more or less of its motion to the latter let it be conceived that the particle acquires a tendency to move and that nevertheless it does not move it is then in a condition totally different from that in which it was at first a cause competent to produce motion is operating upon it but for some reason or other is unable to give rise to motion if the obstacle is removed the energy which was there but could not manifest itself at once gives rise to motion while the restraint last the energy of the particle is merely potential and the case suppose illustrates what is meant by potential energy in this contrast of the potential with the actual modern physics is turning to account the most familiar of Aristotle distinctions that between unanimous and energy that kinetic energy appears to be imparted by impact is a fact of daily and hourly experience we see body set in motion by bodies already in motion which seem to come in contact with them it is a truth which could have been learned by nothing but experience and which cannot be explained but must be taken as an ultimate fact about which explicable or inexplicable there can be no doubt strictly speaking we have no direct apprehension of any other cause of motion but experience furnishes innumerable examples of the production of kinetic energy in a body previously at rest when no impact is discernible as the cause of that energy in all such cases the presence of a second body is a necessary condition and the amount of kinetic energy which its presence enables the first to gain is strictly dependent on the relative positions of the two hence the phrase energy of position which is frequently used as equivalent to potential energy if a stone is picked up and held say six feet above the ground it has potential energy because if let go it will immediately begin to move towards the earth and this energy may be said to be energy of position because it depends upon the relative position of the earth and the stone the stone is solicited to move but cannot so long as the muscular strength of the holder prevents the solicitation from taking effect the stone therefore has potential energy which becomes kinetic if it is let go and the amount of that kinetic energy which will be developed before it strikes the earth depends on its position on the fact that it is say six feet off the earth neither more nor less moreover it can be proved that the razor of the stone had to exert as much energy in order to place it in its position as it will develop in falling hence the energy which was exerted and apparently exhausted in raising the stone is potentially in the stone in its raised position and will manifest itself when the stone is set free thus the energy withdrawn from the general stock to raise the stone is returned when it falls and there is no change in the total amount energy as a whole is conserved taking this as a very broad and general statement of the essential facts of the case the raising of the stone is intelligible enough as a case of the communication of motion from one body to another but the potential energy of the raised stone is not so easily intelligible to all appearance there is nothing either pushing or pulling it towards the earth or the earth towards it and yet it is quite certain that the stone tends to move towards the earth and the earth towards the stone in the way defined by the law of gravitation in the currently accepted language of science the cause of motion in all such cases as this when bodies tend to move towards or away from one or another without any discernible impact of other bodies is termed a force which is called attractive in the one case and repulsive in the other and such attractive or repulsive forces are often spoken of as if they were real things capable of exerting a pull or a push upon the particles of matter concerned thus the potential energy of the stone is commonly said to be due to the force of gravity which is continually operating upon it another illustration may make the case planar the bob of a pendulum swings first to one side and then to the other of the center of the arc which it describes suppose it to have just reached the summit of its right hand half swing it is said that the attractive forces of the bob for the earth and of the earth for the bob set the former in motion as these forces are continually in operation they confer an accelerated velocity on the bob until when it reaches the center of its swing it is so to speak fully charged with kinetic energy if at this moment the whole material universe except the bob were abolished it would move forever in the direction of a tangent to the middle of the arc described as a matter of fact it is compelled to travel through its left hand half swing and thus virtually to go uphill consequently the attractive forces of the bob and the earth are now acting against it and constitute a resistance which the charge of kinetic energy has to overcome but as this charge represents the operation of the attractive forces during the passage of the bob through the right hand half swing down to the center of the arc so it must needs be used up by the passage of the bob upwards from the center of the arc to the summit of the left hand half swing hence at this point the bob comes to a momentary rest the last fraction of kinetic energy is just neutralized by the action of the attractive forces and the bob has only potential energy equal to that with which it started so that the sum of the phenomena may be stated thus at the summit of either half arc of its swing the bob has a certain amount of potential energy as it descends it gradually exchanges this for kinetic energy until at the center it possesses an equal amount of kinetic energy from this point onwards it gradually loses kinetic energy as it descends until at the summit of the other half arc it has acquired an exactly similar amount of potential energy thus on the whole transaction nothing is either lost or gained the quantity of energy is always the same but it passes from one form into the other to all appearance the phenomena exhibited by the pendulum are not to be counted for by impact in fact it is usually assumed that corresponding phenomena would take place if the earth and the pendulum were situated in an absolute vacuum and at any conceivable distance from one another if this be so it follows that there must be two totally different kinds of causes of motion the one impact a vera cause of which to all appearance we have constant experience the other attractive or repulsive force a metaphysical entity which is physically inconceivable Newton expressly repudiated the notion of the existence of attractive forces in a sense in which that term is ordinarily understood and he refused to put forward any hypothesis as to the physical cause of the so-called attraction of gravitation as a general rule his successors have been content to accept the doctrine of attractive and repulsive forces without troubling themselves about the philosophical difficulties which it involves but this has not always been the case and the attempt of the sage in the last century to show that the phenomena of attraction and repulsion are susceptible of explanation by his hypothesis of bombardment of ultra mundane particles whether tenable or not has the great merit of being an attempt to get rid of the dual conception of the causes of motion which has hitherto prevailed on this hypothesis the hammering of the ultra mundane corpuscles on the bob confers its kinetic energy on the one hand and takes it away on the other and the state of potential energy means the condition of the bob during the instant at which the energy conferred by the hammering during the one half arc has just been exhausted by the hammering during the other half arc it seems safe to look forward to the time when the conception of attractive and repulsive forces having served its purpose as a useful piece of scientific scaffolding will be replaced by the deduction of the phenomena known as attraction and repulsion from the general laws of motion the doctrine of the conservation of energy which I have endeavored to illustrate is thus defined by the late clerk Maxwell the total energy of any body or system of bodies is a quantity which can either be increased nor diminished by any mutual action of such bodies though it may be transformed into any one of the forms of which energy is susceptible it follows that energy like matter is indestructible and in generable in nature the phenomenal world so far as it is material expresses the evolution and involution of energy its passage from kinetic to the potential condition and back again wherever motion of matter takes place that motion is affected at the expense of part of the total store of energy hence as the phenomena exhibited by living beings in so far as they are material are all molar or molecular motions these are included under the general law a living body is a machine by which energy is transformed in the same sense as a steam engine is so and all its movements molar and molecular are to be accounted for by the energy which is supplied to it the phenomena of consciousness which along with certain transformations of energy cannot be interpolated in the series of these transformations in as much as they are not motions to which the doctrine of the conservation of energy applies and for the same reason they do not necessitate the using up of energy a sensation has no mass and cannot be conceived to be susceptible of movement that a particular molecular motion does give rise to a state of consciousness is experimentally certain but the how and why of the process are just as inexplicable as in the case of the communication of kinetic energy by impact when dealing with the doctrine of the ultimate constitution of matter we found a certain resemblance between the oldest speculations and the newest doctrines of physical philosophers but there is no such resemblance between the ancient and modern views of motion and its causes except in so far as the conception of attractive and repulsive forces may be regarded as the modified descendant of the Aristotelian conception of forms in fact it is hardly too much to say that the essential and fundamental difference between ancient and modern physical science lies in the ascertainment of the true laws of statics and dynamics in the course of the last three centuries and in the invention of mathematical methods of dealing with all the consequences of these laws the ultimate aim of modern physical science is the deduction of the phenomena exhibited by material bodies from physical mathematical first principles whether the human intellect is strong enough to attain the goal set before it may be a question but thither will it surely strive the third great scientific event of our time the rehabilitation of the doctrine of evolution is part of the same tendency of increasing knowledge to unify itself which has led to the doctrine of the creation of energy and this tendency again is mainly a product of the increasing strength conferred by physical investigation on the belief in the universal validity of that orderly relation of facts which we express by the so-called laws of nature the growth of a plant from its seed of an animal from its egg the apparent origin of innumerable living things from mud or from the pre-defined remains of former organisms has furnished the earlier scientific thinkers with abundant analogies suggestive of the conception of a corresponding method of cosmic evolution from a formless chaos to an ordered world which might either continue forever or undergo dissolution into its elements before starting on a new course of evolution it is therefore no wonder that from the days of the Ionian school onwards the view that the universe was the result of such a process that have maintained itself as a leading dogma of philosophy the eministic theories which played so great a part in Neoplatonic philosophy and Gnostic theology are forms of evolution in the 17th century Descartes propounded a scheme of evolution as an hypothesis of what might have been the mode of origin of the world while professing to accept the ecclesiastical scheme of creation as an account of that which existed to existence in the 18th century Kant put forth a remarkable speculation as to the origin of the solar system closely similar to that subsequently adopted by Laplace and destined to become famous under the title of the Nebular Hypothesis the careful observations and the acute reasonings of the Italian geologist of the 17th and 18th centuries the speculations of Leibniz in the Protogeye and of Buffon de la Terre the sober and profound reasonings of Hutton in the latter part of the 18th century all these tended to show that the fabric of the earth itself implied the continuance of processes of natural causation for a period of time as great in relation to human history as the distances of the heavenly bodies from us are in relation to terrestrial standards of measurement the abyss of time began to loom as large as the abyss of space and this revelation to sight and touch of a link here and a link there of a practically infinite chain of natural causes and effects prepared the way as perhaps nothing else has done for the modern form of the ancient theory of evolution in the beginning of the 18th century Dimele made the first serious attempt to apply the doctrine to the living world in the latter part of it Erasmus, Darwin Goethe, Trevoranus and Lamarck took up the work more vigorously and with better qualifications the question of special creation or evolution lay at the bottom of the fierce disputes which broke out in the French Academy between Cuvier and Saint-Hélière and for a time the supporters of biological evolution were silenced if not answered by the alliance of the greatest naturalist of the age with their ecclesiastical opponents Catastrophism a short-sighted teleology and a still more short-sighted orthodoxy joined forces to crush evolution Lyell and Pulitz Scrope in this country resumed the work of the Italians and of Hutton and the former aided by a marvelous power of clear exposition placed upon an irrefragable basis the truth that natural causes are competent to account for all events which can be proved to have occurred in the course of the secular changes which have taken place during the deposition of the stratified rocks the publication of the Principles of Geology in 1830 constituted an epic in geological science but it also constituted an epic in the modern history of the doctrines of evolution by raising in the mind of every intelligent reader this question if natural causation is competent to account for the not living part of our globe why should it not account for the living part by keeping this question before the public for some 30 years Lyell though the keenest and most formidable of the opponents of the transmutation theory as it was formulated by Lamarck was of the greatest possible service in facilitating the reception of the sounder doctrines of later day and in like fashion another vehement opponent of the transmutation of species the elder Agassiz was doomed to help the cause he hated Agassiz not only maintained the fact of the progressive advance in organization of the inhabitants of the earth in the process of geological epic but he insisted upon the analogy of the steps of this progression with those by which the embryo advances to the adult condition among the highest forms of each group in fact in endeavoring to support these views he went a good way beyond the limits of any cautious interpretation of the facts then known although little acquainted with biological science we will seems to have taken particular pains with that part of his work with the history of geological and biological speculation and several chapters of his 17th and 18th books which comprise the history of physiology of comparative anatomy and of the paleotelogical sciences vividly reproduced the controversies of the early days of the Victorian epic but here as in the case of the doctrine of the conservation of energy the historian of the inductive sciences has no prophetic insight not even a suspicion of that which the near future was to bring forth and those who still repeat the once favorite objection that Darwin's origin of species is nothing but a new version of the philosophie zoologique we'll find that so late as 1844 we will had not the slightest suspicion of Darwin's main theorem even as a logical possibility in fact the publication of that theorem by Darwin and Wallace in 1859 took all the biological world by surprise neither those who were inclined towards the progressive transmutation or development doctrine as it was then called nor those who were opposed to it had the slightest suspicion that the tendency to variation in living beings which all admitted as a matter of fact the selective influence of conditions which no one could deny to be a matter of fact when his attention was drawn to the evidence and the occurrence of great geological changes which also was a matter of fact could be used as the only necessary postulates of a theory of the evolution of plants and animals which even if not at once competent to explain all the known facts of biological science could not be shown to be inconsistent with any so far as biology is concerned the publication of the origin of species for the first time put the doctrine of evolution in its application to living things upon a sound scientific foundation it became an instrument of investigation and in no hands that it proved more brilliantly profitable than in those of Darwin himself his publications on the effects of domestication in plants and animals on the influence of cross fertilization on flowers as organs for affecting such fertilization on insectivorous plants on the motions of plants pointed out the roots of exploration which have since been followed by hosts of inquirers the great prophet of science Darwin found the biological world a more than sufficient field for even his great powers and left the cosmical part of the doctrine to others not much has been added to the nebula hypothesis since the time of Laplace except that the attempt to show against that hypothesis that all nebulae are star clusters has been met by the spectroscopic proof of the gaseous condition of some of them moreover, physicists of the present generation appear now to accept the secular cooling of the earth which is one of the corollaries of that hypothesis in fact, attempts have been made by the help of deductions from the data of physics to lay down an approximate limit to the number of millions of years which have elapsed since the earth was habitable by living beings if the conclusions thus reached should stand the test of further investigation they will undoubtedly be very valuable but whether true or false they can have no influence upon the doctrine of evolution in its application to living organisms the occurrence of successive forms of life upon our globe is an hysterical fact which cannot be disputed and the relation of these successive forms as stages of evolution of the same type is established in various cases the biologist has no means of determining the time over which the process of evolution has extended but accepts the computation of the physical geologist and the physicist whatever that may be evolution as a philosophical doctrine applicable to all phenomena whether physical or mental whether manifested by material atoms or by men in society has been dealt with systematically in the synthetic philosophy of Mr. Herbert Spencer comment on that great undertaking would not be in place here I mention it because so far as I know there are still unscientific principles with modern scientific facts and speculations for the philosophic positive of Mr. Comte with which Mr. Spencer's system of philosophy is sometimes compared though it professes a similar object is unfortunately permeated by a thoroughly unscientific spirit and its author had no adequate acquaintance with the physical sciences even of his own time the doctrine of evolution of the material cosmos is concerned postulates the fixity of the rules of operation of the causes of motion in the material universe if all kinds of matter are modifications of one kind and if all modes of motion are derived from the same energy the orderly evolution of physical nature out of one substratum and one energy implies that the rules of action of that energy should be fixed and definite in the past history of the universe there is no room for chance or disorder but it is possible to raise the question whether this universe of simplest matter and definitely operating energy which forms our hypothetical starting point may not itself be a product of evolution from a universe of such matter in which the manifestations of energy were not definite in which for example our laws of motion held good for some units and not for others or for the same units at one time not at another and which would therefore be a real epicurean chance world for myself I must confess that I find the error of this region of speculation too rarefied for my constitution and I am disposed to take refuge in ignoramus a ignorabimus the execution of my further task the indication of the most important achievements in the several branches of physical science during the last 50 years is embarrassed by the abundance of the objects of choice and by the difficulty which everyone but a specialist in each department must find in drawing a due distinction between discoveries which strike the imagination by their novelty or by their practical influence and those unobtrusive but pregnant observations and experiments in which the germs of the great things of the future really lie moreover, my limits restrict me too little more than a bare chronicle of the events which I have to notice in physics and chemistry the old boundaries of which sciences are rapidly becoming effaced one can hardly go wrong in ascribing a primary value to the investigations into the relation between the solid liquid and gaseous states of matter on the one hand and degrees of pressure and of heat on the other almost all even the most refractory solids have been vaporized by the intense heat of the electric arc and the most refractory gases have been forced to assume the liquid and even the solid forms by the combination of high pressure with intense cold it has further been shown that there is no discontinuity between these states that a gas passes into the liquid state through a condition which is neither one nor the other and that a liquid body becomes solid or a solid liquid by the intermediation of a condition in which it is neither truly solid nor truly liquid theoretical and experimental investigations have concurred in the establishment of the view that a gas is a body the particles of which are in incessant rectilinear motion at high velocities colliding with one another and bounding back when they strike the walls of the containing vessel and on this theory the already ascertained relations of gaseous bodies to heat and pressure have been shown to be deducible from mechanical principles immense improvements have been affected in the means of exhausting a given space of gaseous contents an experimentation on the phenomena which attend the electric discharge and the action of radiant heat within the extremely rarefied media thus produced has yielded a great number of remarkable results some of which have been made familiar to the public by the geysler tubes and the radiometer already these investigations have afforded an unexpected insight into the constitution of matter and its relations with thermal and electric energy and they open up a vast field for future inquiry into some of the deepest problems of physics other important steps in the same direction have been affected by investigations into the absorption of radiant heat proceeding from different sources by solid, fluid and gaseous bodies and it is a curious example of the interconnection of the various branches of physical science that some of the results thus obtained have proved of great importance in meteorology the existence of numerous dark lines constant in their number and position in the various regions of the solar spectrum was made out by Fraunhofer in the early part of the present century but more than 40 years elapsed before their causes were ascertained and their importance recognized spectroscopy which then took its rise is probably that employment of physical knowledge already won as a means of further acquisition which most impresses the imagination for it has suddenly and immensely enlarged our power of overcoming the obstacles which almost infinite minuteness on the one hand and almost infinite distance on the other have hitherto opposed to the recognition of the presence and the condition of matter one 18 millionth of a grain of sodium in the flame of a spirit lamp may be detected by this instrument and at the same time it gives trustworthy indications of the material constitution not only of the sun but of the farthest of those fixed stars and nebulae which afford sufficient light to affect the eye or the photographic plate of the inquirer the mathematical and experimental elucidation of the phenomena of electricity and the study of the relations of this form of energy and chemical and thermal action had made extensive progress before 1837 but the determination of the influence of magnetism on light the discovery of diamagnetism of the influence of crystalline structure on magnetism and the completion of the mathematical theory of electricity all belong to the present epic to it also appertain the practical execution and the working out of the results of the great international system of observations on terrestrial magnetism suggested by Humboldt in 1836 and the invention of instruments of infinite delicacy and precision for the quantitative determination of electrical phenomena the voltaic battery has received vast improvements while the invention of magneto-electric engines and of improved means of producing ordinary electricity has provided sources of electrical energy vastly superior than any before accident in power and far more convenient for use it is perhaps this branch of physical science which may claim the palm for its practical fruits no less than for the aid which it has furnished to the investigation of other parts of the field of physical science the idea of the practicability of establishing a communication between distant points by means of electricity could hardly fail to have simmered in the minds of ingenious men since well nigh a century ago experimental proof was given that electric disturbances could be propagated through a wire 12,000 feet long various methods of carrying the suggestion into practice had been carried out with some degree of success but the system of electric telegraphy which at the present time brings all parts of the civilized world within a few minutes of one another originated only about the commencement of the epic under consideration in its influence on the course of human affairs this invention takes its place besides that of gunpowder which tended to abolish the physical inequalities of fighting men of printing which tended to destroy the effective inequalities in wealth among learning men of steam transport which has done the like for traveling men all these gifts of science are aids in the process of leveling up of removing the ignorant and baneful prejudices of nation against nation province against province and class against class of assuring that social order which is the foundation of progress which has redeemed Europe from barbarism and against which one is glad to think that those who in our time are employing themselves in fanning the embers of ancient wrong in setting class against class and in trying to tear asunder the existing bonds of unity are undertaking a futile struggle the telephone is only second in practical importance to the electric telegraph invented as it were only the other day it has already taken its place as an appliance of daily life sixty years ago the extraction of metals from their solutions by the electric current was simply a highly interesting scientific fact at the present day the galvanoplastic art is a great industry and in combination with photography promises to be of endless service in the arts electric lighting is another great gift of science to civilization the practical effects of which have not yet been fully developed largely on account of its cost but those whose memories go back to the tinderbox period and recollect the cost of the first Lucifer matches will not despair of the results of the application of science and ingenuity to the cheap production of anything for which there is a large demand end of section three this has been a LibriVox recording all LibriVox recordings are in the public domain