 Chapter 40 of Principles of Geology This is a LibriVox recording. A LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org Recording by Dion Jones, Salt Lake City, Utah. Principles of Geology by Charles Lyle Chapter 40 Part 1 Theories respecting the original introduction of species Proposal of and hypothesis on this subject Supposed centers or foci of creation Why distinct provinces of animals and plants Have not become more blended together Brockey's speculation on the loss of species Stations of plants and animals Causes on which they depend Stations of plants, how affected by animals Equilibrium in the number of species, how preserved Peculiar efficacy of insects in this task Rapidity with which certain insects multiply Or decrease in numbers Effect of omnivorous animals In preserving the equilibrium of species Reciprocal influence of aquatic and terrestrial species On each other Theory of Linnaeus It would be superfluous to examine the various attempts Which were made to explain the phenomena of the distribution of species Alluded to in the preceding chapters In the infancy of the sciences of botany, zoology, and physical geography The theories, or rather conjectures, then indulged Now stand refuted by a simple statement of facts And if Linnaeus were living He would be the first to renounce the notions which he promulgated For he imagined the habitable world to have been For a certain time limited to one small tract The only portion of the Earth's surface that was as yet laid bare By the subsidence of the primeval ocean In this fertile spot he supposed the originals of all the species of plants Which exist on this globe to have been congregated together With the first ancestors of all animals and of the human race In Quacomode, Habitaverant, Anamellia, Omnia At Vegetablia, Leite, Germana Verant In order to accommodate the various habitudes of so many creatures And to provide a diversity of climate suited to their several natures The tract in which the creation took place Was supposed to have been situated in some warm region of the Earth But to have contained a lofty mountain range on the heights And in the declivities of which were to be found all temperatures And every climate from that of the torrid to that of the frozen zone That there was never a universal ocean since the planet was inhabited Or rather since the oldest groups of strata yet known to contain organic remains were formed Is proved by the presence of terrestrial plants Or by indication of shores in all the older formations And if this conclusion was not established yet no geologist could deny That since the first small portion of the Earth was laid dry There have been many entire changes in the species of plants and animals inhabiting the land But without dwelling on the above and other refuted theories Let us inquire whether some hypothesis cannot be substituted as simple as that of Linnaeus To which the phenomena now ascertained in regard to the distribution Both of aquatic and terrestrial species may be referred The following may perhaps be reconcilable with known facts Each species may have had its origin in a single pair or individual where an individual was sufficient And species may have been created in succession at such times and in such places As to enable them to multiply and endure for an appointed period And occupy an appointed space on the globe In order to explain this theory let us suppose every living thing to be destroyed in the western hemisphere Both on the land and in the ocean And permission to be given to man to people this great desert By transporting into it animals and plants from the eastern hemisphere A strict prohibition being enforced against introducing two original stocks of the same species Now it is easy to show that the result of such a mode of colonizing would correspond exactly So far as regards the grouping of animals and plants with that now observed throughout the globe In the first place it would be necessary for naturalists Before they imported species into particular localities To study attentively the climate and other physical conditions of each spot It would be no less requisite to introduce the different species in succession So that each plant and animal might have time and opportunity to multiply Before the species destined to prey upon it was admitted Many herbs and shrubs for example must spread far and wide Before the sheep, the deer and the goat could be allowed to enter Lest they should devour and annihilate the original stocks of many plants And then perish themselves for want of food The above mentioned herbivorous animals in their turn Must be permitted to make considerable progress before the entrance of the first pair of wolves or lions Insects must be allowed to swarm before the swallow could be permitted to skim through the air And feast on thousands at one repast It is evident that however equally in this case our original stocks were distributed Over the whole surface of land and water There would nevertheless arise distinct botanical and zoological provinces For there are a great many natural barriers which oppose common obstacles To the advance of a variety of species Thus for example almost all the animals and plants naturalized by us Towards the extremity of South America would be unable to spread beyond a certain limit Towards the east, west and south because they would be stopped by the ocean And a few of them only would succeed in reaching the cooler latitudes of the northern hemisphere Because they would be incapable of bearing the heat of the tropics Through which they must pass In the course of ages undoubtedly exceptions would arise And some species might become common to the temperate and polar regions Or both sides of the equator For I have before shown that the powers of diffusion Converred on some classes are very great But we might confidently predict that these exceptions would never become so numerous As to invalidate the general rule Some of the plants and animals transplanted by us To the coast of Chile and Peru would never be able to cross the Andes So as to reach the eastern plains Nor for a similar reason would those first established in the Pampas Or the valleys of the Amazon and the Orinoco Ever arrive at the shores of the Pacific In the ocean and analogous state of things would prevail For there also climate would exert a huge influence In limiting the range of species And the land would stop the migrations of aquatic tribes As effectually as the sea arrests the dispersion of the terrestrial As certain birds, insects and the seeds of plants Can never cross the direction of prevailing winds So currents form natural barriers to the dissemination of many oceanic races A line of shoals may be as impassable to deep water species As are the alps and the Andes to plants and animals peculiar to plains While deep abysses may prove insuperable obstacles To the migration of the inhabitants of shallow waters Supposed centers or foci of creation It is worthy of observation that one effect of the introduction of single pairs of each species Must be the confined range of certain groups in spots Which, like small islands or solitary inland lakes Have few means of interchanging their inhabitants with adjoining regions Now this congregating in a small space of many peculiar species Would give an appearance of centers or foci of creation As they have been termed as if they were favorite points Where the creative energy has been in greater action than in others And where the numbers of peculiar organic beings Have consequently become more considerable I do not mean to call in question the soundness of the inferences of some botanists As to the former existence of certain limited spots When species of plants have been propagated radiating as it were In all directions from a common center On the contrary, I conceive these phenomena to be the necessary consequences Of the plan of nature before suggested Operating during these successive mutations of the surface Some of which the geologist can prove to have taken place Subsequently to the period when many species now existing were created In order to exemplify how this arrangement of plants may have been produced Let us imagine that about three centuries before the discovery of St. Helena It's self of submarine volcanic origin A multitude of new islands had been thrown up in the surrounding sea And that these had each become clothed with plants emigrating from St. Helena In the same manner as the wild plants of Campania have diffused themselves over Montenovo Whenever the first botanist investigated the new archipelago He would in all probability find a different assemblage of plants In each of the islands of recent formation But in St. Helena itself he would meet with individuals of every species Belonging to all parts of the archipelago And some in addition peculiar to itself That is those which had not been able to obtain a passage Into any one of the surrounding new formed lands In this case it might be truly said that the original island Was the primitive focus or center of a certain type of vegetation Whereas in the surrounding islands there would be a smaller number of species Yet all belonging to the same group But this peculiar distribution of plants would not warrant the conclusion that In the space occupied by St. Helena There had been a greater exertion of creative power Than in the spaces of equal area occupied by the new adjacent lands Because within the period in which St. Helena had acquired its peculiar vegetation Each of the spots supposed to be subsequently converted into land May have been the birthplace of a great number of marine animals and plants Which may have had time to scatter themselves far and wide over the southern Atlantic Why distinct provinces not more blended Perhaps it may be objected to some parts of the foregoing train of reasoning That during the laps of past ages Especially during many partial revolutions of the globe of comparatively modern date Different zoological and botanical provinces ought to have become more confounded And blended together That the distribution of species approaches too nearly To what might have been expected if animals and plants had been introduced into the globe When its physical geography had already assumed the features which it now wears Whereas we know that in certain districts Considerable geographical changes have taken place since species identical With those now in being were created Brockey's speculations on loss of species These and many kindred topics cannot be fully discussed Until we have considered not merely the general laws Which may regulate the first introduction of species But those which may limit their duration on the earth Brockey remarked when hazarding some interesting conjectures Respecting the loss of species That a modern naturalist had no small assurance Who declared that individuals alone were capable of destruction And that species were so perpetuated That nature could not annihilate them so long as the planet lasted Or at least that nothing less than the shock of a comet Or some similar disaster could put an end to their existence The Italian geologist on the contrary Had satisfied himself that many species of Testatia Which formally inhabited the Mediterranean Had become extinct Although a great number of others Which had been the contemporaries of those lost races Still survived He came to the opinion that about half the species Which peopled the waters When the sub-Apanine strata were deposited Had gone out of existence But in this inference he does not appear to have been far wrong But instead of seeking a solution of this problem Like some other geologist of his time In a violent and general catastrophe Brockey endeavored to imagine some regular and constant law By which species might be made to disappear From the earth gradually and in succession The path he suggested of a species might depend Like that of individuals on certain peculiarities Of constitution conferred upon them at their birth And as the longevity of the one depends on a certain force of vitality Which after a period grows weaker and weaker So the duration of the other may be governed By the quantity of prolific power bestowed upon the species Which after a season may decline in energy So that the fecundity and multiplication of individuals May be gradually lessened from century to century Until that fatal term arrives When the embryo incapable of extending And developing itself abandons Almost at the instant of its formation The slender principle of life by which it was scarcely animated And so all dies with it Now we may coincide in opinion with the Italian naturalist As to the gradual extinction of species one after another By the operation of regular and constant causes Without admitting an inherent principle of deterioration In their physiological attributes We might concede that many species are on the decline And that the day is not far distant when they will cease to exist Yet deem it consistent with what we know of the nature of organic beings To believe that the last individuals of each species Retain their prolific powers in their full intensity Brachy has himself speculated on the share Which a change of climate may have had In rendering the Mediterranean unfit For the habitation of certain testacea Which still continued to thrive in the Indian Ocean And of others which were now only represented By analogous forms within the tropics He must also have been aware that other extrinsic causes Such as the progress of human population Or the increase of some one of the inferior animals Might gradually lead to the extirpation of a particular species Although its fecundity might remain to the last unimpaired If, therefore, amid the vicissitudes of the animate and inanimate world There are known causes capable of bringing about the decline And extirpation of species It became him thoroughly to investigate the full extent To which these might operate before he speculated On any cause of so purely hypothetical a kind As the demunation of the prolific virtue If it could have been shown that some wild plant Had insensibly dwindled away and died out As sometimes happens to cultivated varieties Obligated by cuttings, even though climate, soil And every other circumstance should continue identically the same If any animal had perished while the physical condition Of the earth and the number and force of its foes With every other extrinsic cause remain unaltered Then might we have some ground for suspecting That the infirmities of age creep on as naturally Species as upon individuals But in the absence of such observations Let us turn to another class of facts And examine, attentively, the circumstances Which determine the stations of particular animals and plants And perhaps we shall discover in the vicissitudes To which these stations are exposed A cause fully adequate to explain the phenomena Under consideration, stations of plants and animals Stations comprehend all the circumstances Whether relating to the animate or inanimate world Which determine whether a given plant or animal Can exist in a given place So that if it be shown that stations can become Essentially modified by the influence of known causes It will follow that species as well as individuals are mortal Every naturalist is familiar with the fact That although in a particular country such as Great Britain There may be more than 3,000 species of plants 10,000 insects and a great variety in each of the other classes Yet there will not be more than 100 Perhaps not half that number inhabiting any given locality There may be no want of space in the supposed tract It may be a large mountain or an extensive moor Or a great river plain containing room enough For individuals of every species in our island Yet the spot will be occupied by a few To the exclusion of many Yet these few are enabled throughout long periods To maintain their ground successfully Against every intruder Notwithstanding the facilities which species enjoy By virtue of their power of diffusion Of invading adjacent territories The principal causes which enable a certain assemblage of plants Thus to maintain their ground against all others depend This is well known on the relations between The physiological nature of each species And the climate, exposure, soil and other physical conditions Of the locality Some plants live only on rocks Others in meadows, a third class in marshes Of the latter, some delight in a freshwater morass Others in salt marshes Where their roots may copiously absorb saline particles Some prefer an alpine region in a warm latitude Where during the heat of summer they are constantly Irrigated by the cool waters of melting snows To others loose sand so fatal to the generality Of species affords the most proper station Parox aerinaria and the Elemus aerinarius Acquire their full vigor on a sandy dune Obtaining an ascendancy over the very plants Which in a stiff clay would immediately stifle them Where the soil of a district is of so peculiar a nature That it is extremely favorable to certain species And agrees ill with every other The former get exclusive possession of the ground And as in the case of heaths live in societies In like manner the bog moss sphagnum Is fully developed in peaty swamps And becomes like the heath in the language of botanists A social plant, such monopolies however Are not common for they are checked by various causes Not only are many species endowed with equal powers To obtain and keep possession of similar stations But each plant for reasons not fully explained By the physiologist has the property of rendering The soil where it has grown less fitted For the support of other individuals of its own species Or even other species of the same family Yet the same spot so far from being impoverished Is improved for plants of another family Oaks for example render the soil more fertile For the fur tribe and furs prepare the soil for oaks Every agriculturalist feels the force of this law Of the organic world and regulates accordingly The rotation of his crops Equilibrium in the number of species, how preserved All the plants of a given country, says Dave Kendall In his usual spirited style, are at war one with another The first which established themselves by chance In a particular spot, tend by the mere occupancy Of space to exclude other species The greater choked the smaller, the longest Livers replace those which last for a shorter period The more prolific gradually make themselves masters Of the ground which species multiplying more slowly Would otherwise fill. In this continual strife It is not always the resources of the plant itself Which enable it to maintain or extend its ground Its success depends in a great measure On the number of its foes or allies Among the animals and plants inhabiting the same region Thus for example, a herb which loves the shade May multiply if some tree with spreading boughs And dense foliage flourish in the neighborhood Another which, if unassisted, would be overpowered By the rank growth of some hardy competitor Because its leaves are unpalatable to cattle Which, on the other hand, annually crop down its antagonist And rarely suffer it to ripen its seed Oftentimes we see some herb which has flowered In the midst of a thorny shrub When all the other individuals of the same species In the open fields around are eaten down And cannot bring their seed to maturity In this case the shrub has lent his armor Of spines and prickles to protect the defenseless herb Against the mouths of the cattle and thus a few individuals Which occupied perhaps the most unfavorable station In regard to exposure, soil, and other circumstances May, nevertheless, by the aid of an ally Become the principal source whereby the winds Are supplied with seeds which perpetuate the species Throughout the surrounding tract. Thus in the new forest In Hampshire the young oaks which are not consumed By the deer or uprooted by the swine Are indebted to the holly for their escape In the above examples we see one plant shielding Another from the attacks of animals Which are numerous where some animal defends a plant Against the enmity of some other subject of the vegetable kingdom Scarcely any beast observes a Swedish naturalist Will touch the nettle, but fifty different kinds Of insects are fed by it. Some of these Sees upon the root, others upon the stem Some eat the leaves, others devour the seeds and flowers This multitude of enemies, the nettle Which is now found in all the four quarters of the globe Would annihilate a great number of plants Linnaeus tells us in his tour in Skania That goats were turned into an island Which abounded with the Augustus erin denacia Where they perished by famine, but horses And the same plant. The goat also he says Thrives on the meadowsweet and water hemlock Plants which are injurious to cattle Chapter 40 Part 2 Of Principles of Geology This is a LibriVox recording. A LibriVox recordings are in the public domain For more information or to volunteer, please visit LibriVox.org, recording by Dionne Jynes Celtic City, Utah. Principles of Geology By Charles Lyall, Chapter 40 Part 2 Agency of Insects Every plant observes, Wilkie, has its proper insect Allotted to it to curb its luxuriancy And to prevent it from multiplying to the exclusion Thus, grass in meadows sometimes flourishes So as to exclude all other plants Here, the fulina griminus, Bambic's Graham, with her numerous progeny, finds a well Spread table. They multiply in immense numbers And the farmer, for some years, laments the failure Of his crop. But the grass being consumed The moths die with hunger, or remove to another place Now the quantity of grass being greatly diminished The other plants, which were before choked By it, spring up, and the ground becomes Variegated with a multitude of different species of flowers Had not nature, given a commission To this minister, for that purpose, the grass would destroy A great number of species of vegetables Of which the equilibrium is now kept up In the above passage, allusion is made to the ravages Committed in 1740 and the two following years In many provinces of Sweden by a most Destructive insect. The same moth is said Never to touch the foxtail grass Classed as a most active ally and benefactor Of that species and as peculiarly Instrumental in preserving it in its present abundance A discovery of Rolander cited in the Treatise of Wilkie above mentioned affords a good Illustration of the checks and counterchecks which Nature has appointed to preserve the balance of power Among species. The fulena strobelella Has the furcone assigned to it to deposit Its eggs upon. The young caterpillars coming out of The shell consume the cone and superfluous seed But lest the destruction should be too general The ignuman strobelella lays its eggs In the caterpillar inserting its long tail In the openings of the cone till it touches the included Insect for its body is too large to enter Thus it fixes its minute egg upon the Caterpillar which being hatched destroys it Entomologists enumerate many parallel cases Where insects appropriated to certain plants Are kept down by other insects and These again by parasites expressly appointed To prey on them. Few perhaps are in the habit Of duly appreciating the extent to which Insects are active in preserving the balance of species Among plants and thus regulating Indirectly the relative numbers of many of the higher Orders of terrestrial animals. The peculiarity Of their agency consists in their power of Suddenly multiplying their numbers to a degree Which could only be accomplished in a considerable Lapse of time in any of the larger animals And then as instantaneously relapsing Without the intervention of any violent disturbing cause Into their former insignificance. If for the sake Of employing on different but rare occasions A power of many hundred horses we were under the Necessity of feeding all these animals at great cost In the intervals when their services were not required We should greatly admire the invention of a machine Such as the steam engine which was capable at Any moment of exerting the same degree of strength Without any consumption of food during periods of inaction The same kind of admiration is strongly excited When we contemplate the powers of insect life In the creation of which the author of nature Has been so prodigal as scanty number of Minute individuals to be detected only by careful research Are ready in a few days, weeks or months To give birth to myriads which may repress Any degree of monopoly in another species Or remove nuisances such as dead carcasses Which might taint the error. But no sooner has the destroying Commission been executed than the gigantic power Becomes dormant. Each of the mighty host Soon reaches the term of its transient existence And arrives when the whole species passes naturally Into the egg and thence into the larva and pupa State. In this defenseless condition it may be Destroyed either by the elements or by the Augmentation of some of its numerous foes Which may prey upon it in the early stages of its transformation Or it often happens that in the following year The season proves unfavorable to the hatching of the eggs Or the development of the pupa. Thus the swarming Myriads depart which may have covered the vegetation Like the aphids or darkened the sky like locusts In almost every season there are some species Which in this manner put forth their strength And then like Milton spirits which thronged the spacious Hall, reduced to smallest forms their shapes Immense. So thick the airy crowd swarmed And were straightened till the signal given Behold a wonder they but how who seemed In bigness to surpass earth's giant suns Now less than smallest dwarfs. A few examples Will illustrate the mode in which this force operates It is well known that among the countless species Of the insect creation some feed on animal Others on vegetable matter. And upon considering A catalog of 8,000 British insects And arachnidae Mr. Kirby found that these Two divisions were nearly a counterpoi to each other The carnivorous being somewhat preponderant But there are also distinct species some appointed To consume living others dead or putrid animal And vegetable substances. One female of Musca Carnaria will give birth to 20,000 young And the larva of many flesh flies devours So much food in 24 hours and grows so quickly As to increase their weight 200 fold In five days after being hatched they arrive At their full growth and size so that there was ground Says Kirby for the assertion of Linnaeus That three flies of Am vomitoria could devour A dead horse as quickly as a lion And another Swedish naturalist remarks that so great Are the powers of propagation of a single species Even of the smallest insects that each can Commit when required more ravages than the elephant Next to locus the aphids perhaps exert The greatest power over the vegetable world and like them Are so sometimes so numerous as to darken the air The multiplication of these little creatures is without Parallel and almost every plant has its peculiar Species. Remur has proved that in five generations One aphis may be the progenitor Of 5,904,900,000 Descendants and it is supposed That in one year there may be 20 generations Mr. Curtis observes that as among Caterpillars we find some that are constantly Ultrably attached to one or more particular species Of plants and others that feed indiscriminately On most sorts of herbage so it is precisely With the aphids some are particular others More general feeders and as they resemble other insects In this respect so they do also in being More abundant in some years than in others In 1793 they were the chief and in 1798 The soul cause of the failure of the haps In 1794 a season almost Unparalleled for drought the hop was perfectly free from them While peas and beans especially the former Suffered very much from their depredations The ravages of the caterpillars of some of our smaller Afford a good illustration of the temporary increase Of a species the oak trees of a considerable wood Have been stripped of their leaves as bare as in winter By the caterpillars of a small green moth Tortrix veridana which has been observed the year following Not to abound the silver white moth Plusia gamma although one of our common species Is not dreaded by us for its devastations But legions of their caterpillars have at times created Alarm in France as in 1735 Remure observes that the female moth lays about 400 eggs so that if 20 caterpillars Were distributed in a garden and all lived through the winter And became moths in the succeeding May The eggs laid by these if half of them were female And all fertile would in the next generation produce 800,000 caterpillars A modern writer therefore justly observes that did not Providence put causes in operation to keep them In due bounds the caterpillars of this moth alone Leaving out of consideration the 2,000 other Moths might soon destroy more than half of our vegetation In the latter part of the last century An ant most destructive to the sugarcane Formica saccharivora appeared in such infinite Hose on the island of Granada as to put a stop To the cultivation of that vegetable Their numbers were incredible, the plantations and roads Domestic quadrupeds together with rats, mice and reptiles And even birds perished in the consequence of this plague It was not till 1780 that they were at length Annihilated by torrents of rain Which accompanied a dreadful hurricane Devastations caused by locusts We may conclude by mentioning some instances of the devastations of locusts In various countries, among other parts of Africa Serenica has been at different periods Infested by myriads of these creatures Which have consumed nearly every green thing The effect of the havoc committed by them May be estimated by the famine they occasioned St. Augustine mentions a plague of this kind in Africa Of over 3000 men in the kingdom of Massinissa alone and many more upon the territories bordering upon the sea. It is also related That in the year 591 an infinite army Of locusts migrated from Africa into Italy And after grievously ravaging the country Were cast into the sea when there arose a pestilence Which carried off nearly a million of men and beasts In the Venetian territory also in 1748 More than 30,000 persons are said to have Perished in a famine occasioned by this Scourge and other instances are recorded of their Devastations in France, Spain, Italy, Germany etc In different parts of Russia also In Poland, in Arabia and India and other countries Their visitations have been periodically experienced Although they have a preference for certain plants Yet when these are consumed they will attack almost all The remainder. In the accounts of the invasion Of locusts the statements which appear most marvelous Relate to the prodigious mass of matter Encumbers the sea whenever they are blown into it And the pestilence arising from its putrefaction Their dead bodies are said to have been in some places Heaped one upon another to the depth of four feet In Russia, Poland and Lithuania And when in southern Africa they were driven into the sea By a northwest wind they formed Cezbero Along the shore for 50 miles a bank three or four feet high But when we consider that forests are Stripped of their foliage and the earth of its green garment For thousands of square miles it may well be Supposed that the volume of animal matter produced May equal that of great herds of quadrupeds And flights of large birds suddenly precipitated into the sea The occurrence of such events at certain Intervals in hot countries like the severe winters And damp summers returning after a series of years In the temperate zone may affect the Proportional numbers of almost all classes of animals And plants and probably prove fatal to the existence Of many which would otherwise thrive there While on the contrary the same occurrences can Scarcely fail to be favorable to certain species Which if deprived of such aid might not maintain Their ground although it may usually be remarked That the extraordinary increase of some one species Is immediately followed and checked by the multiplication Of another yet this does not always happen Partly because many species feed in common On the same kinds of food and partly because Many kinds of food are often consumed Indifferently by one and the same species In the former case where a variety of different animals Have precisely the same taste as for example When many insectivorous birds and reptiles Are fly or beetle the unusual numbers of these insects May cause only a slight and almost imperceptible Augmentation of each of these species of bird and reptile In the other instances where one animal Prays on others of almost every class as for example Where our English buzzards devour not only Small quadrupeds as rabbits and field mice But also birds frogs lizards and insects The profusion of any one of these last may cause All such general feeders to subsist more Exclusively upon the species thus in excess By which means the balance may be restored Agency of omnivorous animals the number of species Which are nearly omnivorous is considerable Every animal has perhaps a predilection For some one description of food rather than another Yet some are not even confined to one of the great kingdoms Of the organic world thus when the raccoon Of the West Indies can procure neither fowls Fish snails nor insects it will attack The sugar canes and devour various kinds of grain Civets when animal food is scarce maintain themselves On fruits and roots numerous birds which feed Indiscriminately on insects and plants are perhaps More instrumental than any other of the Terrestrial tribes in preserving a constant equilibrium Between the relative numbers of different classes of animals And vegetables if the insects become very numerous And devour the plants these birds will immediately Derive a larger portion of their subsistence From insects just as the Arabians, Syrians And hotentots feed on locusts when the locusts Devour their crops reciprocal influence Of aquatic and terrestrial species The intimate relation of the inhabitants of the water And the land and the influence exerted by each On the relative number of species must not be overlooked Amongst the complicated causes which determine the existence Of animals and plants in certain regions A large portion of the amphibious quadrupeds and reptiles Pray partly on aquatic plants and animals And in part on terrestrial and a deficiency One kind of prey causes them to have immediate recourse To the other the veracity of certain insects As the dragonfly for example is confined to the water During one stage of their transformations and in their Perfect state to the air innumerable water birds Both of rivers and seas derive in like manner Their food indifferently from either element so that The abundance or scarcity of prey in one induces Them either to forsake or more constantly to Haunt the other thus an intimate connection Between the state of the animate creation in a lake Or river and in the adjoining dry land is maintained Or between a continent with its lakes and rivers And the ocean it is well known that many birds Migrate during stormy seasons from the seashore Into the interior in search of food while others On the contrary urged by like once forsake their Inland haunts and live on substances rejected By the tide the migration of fish into Rivers during the spawning season supplies another link Of the same kind suppose the salmon to be reduced By numbers by some marine foes as by seals And grampuses the consequence must often be That in the course of a few years the otters At the distance of several hundred miles inland will be Lessened in number from the scarcity of fish On the other hand if there be a dearth of food For the young fry of the salmon in rivers and estuaries That are burned to the sea the sand eels and other marine Species which are usually kept down by the salmon Will swarm in greater perfusion it is unnecessary To accumulate a greater number of illustrations In order to prove that the stations of different plants And animals depend on a great complication of Circumstances on an immense variety of relations In the state of the inanimate worlds every plant Requires a certain climate soil and other conditions And often the aid of many animals in order to Maintain its ground many animals feed on certain plants Being often restricted to a small number And sometimes to one only other members of the animal kingdom Feed on plant eating species and thus Become dependent on the conditions of the stations Not only of their prey but of the plants consumed By them having duly reflected on the nature And extent of these mutual relations in the different parts Of the organic and inorganic worlds we may Next proceed to examine the results which may be anticipated From the fluctuations now continually Progress in the state of the earth's surface And in the geographical distribution of its living productions End of Chapter 40 Part 2 Chapter 41 of Principles of Geology This is a LibriVox recording all LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Recording by Sycamore Rockwell Translations of Geology by Charles Lyle Extinction of Species Changes in the stations of animals Extension of the range of one species alters the condition of many others The first appearance of a new species causes the chief disturbance Changes known to have resulted from the advance of human population Whether man increases the productive powers of the earth Indigenous quadrupeds and birds extirpated in Great Britain Propagation of the dodo Rapid propagation of domestic quadrupeds in America Power of exterminating species no prerogative of man Concluding remarks We have seen that the stations of animals and plants depend not merely On the influence of external agents in the inanimate world And the relations of that influence to the structure and habits of each species But also on the state of the contemporary living beings Which inhabit the same part of the globe In other words, the possibility of the existence of a certain species In a given place or of its thriving more or less therein Is determined not merely by temperature, humidity, soil, elevation And other circumstances of the like But also by the existence or non-existence The abundance or scarcity of a particular assemblage of other plants And animals in the region If it be shown that both these classes of circumstances Whether relating to the animate or inanimate creation Are perpetually changing It will follow that species are subject to incessant vicissitudes And if the result of these mutations In the course of ages be so great as materially to affect The general condition of stations It will follow that the successive destruction of species Must now be part of the regular and constant order of nature The expansion of the range of one species alters the condition of the others It will be desirable first to consider the effects which Every extension of the numbers or geographical range of one species Must produce on the condition of others inhabiting the same regions When the necessary consequences of such extensions have been fully explained The reader will be prepared to appreciate the important influence Which slight modifications in the physical geography of the globe May exert on the condition of organic beings In the first place it is clear that when any region is stacked With as great a variety of animals and plants As the productive powers of that region will enable it to support The addition of any new species Or the permanent numerical increase of one previously established Must always be attended either by the local extermination Or the numerical decrease of some other species May undoubtedly be considerable fluctuations from year to year And the equilibrium may be again resorted without any permanent alteration For in particular seasons a great supply of heat, humidity or other causes May augment the total quality of vegetable produce In which case all the animals subsiding on vegetable food And others which prey on them May multiply without any one species giving way But will as the aggregate quantity of vegetable produce remains unaltered The progressive increase of one animal or plant Implies the decline of another All agriculturists and gardeners are familiar with the fact that When weeds intrude themselves into the space appropriated to cultivate species The latter are starved in their growth or stifled If we abandon for a short time a field or garden A host of indigenous plants pour in and obtain the mastery Extrapating the exotics or putting an end to the monopoly of some native plants If we enclose a park and stock it with as many deer as the herbage will support We cannot add sheep without lessening the number of the deer Nor can other herbivorous species be subsequently introduced Unless the individuals of each species in the park become fewer in proportion So if there be an island where leopards are the only beasts of prey And the lion tiger and hyena afterwards enter The leopards if they stand their ground will be reduced in number If the locusts then arrive and swarm greatly They may deprive a large number of plant eating animals of their food And thereby cause a famine Not only among them but among the beasts of prey Certain species perhaps which had the weakest footing in the island May thus be annihilated We have seen how many distinct geographical provinces there are Of aquatic and terrestrial species And how great are the powers of migration confirmed on different classes Whereby the inhabitants of one region may be enabled from time to time To invade another and do actually so migrate and diffuse themselves Over new countries Now although our knowledge of the history of the animate creation Dates from so recent a period that we can scarcely trace the advance Or decline of any animal or plant Except in those cases where the influence of man has intervened Yet we can easily conceive what must happen when some new colony of wild animals Or plants enters a region for the first time And succeeds in establishing itself Supposed effect of the first entrance of the polar bear into Iceland Let us consider how great are the devastations committed at certain periods By the Greenland bears When they are drifted to the shores of Iceland in considerable numbers on the ice These periodical invasions are formidable even to man So that when the bears arrive the inhabitants collect together And go in pursuit of them with firearms Each native who slays one being rewarded by the king of Denmark The Danes of old, when they landed in their marauding expeditions upon our coast Hardly excited more alarm Nor did our islanders muster more promptly for the defence of their lives And property against the common enemy Than the modern Icelanders against these formidable brutes It often happens says Henderson That the natives are pursued by the bear when he has been long at sea And when his natural ferocity has been heightened by the keenness of hunger If unarmed it is frequently by stratagem only that they make their escape Let us cast our thoughts back to the period when the first polar bears reached Iceland Before it was colonised by the Norwegians in 1874 We may imagine the breaking up of an immense barrier of ice Like that which in 1816 and the following year disappeared from the east coast of Greenland Which it had surrounded for four centuries By the aid of such means of transportation A great number of these quadrupeds might effect a landing at the same time And the havoc which they would make among the species previously settled in the island Would be terrific The deer, foxes, seals and even birds on which these animals sometimes prey Would be soon thinned down But this would be a part only And probably an insignificant portion of the aggregate amount of change Brought about by the new invader The plants on which the deer fed Being less consumed in consequence of the lessened numbers of that herbivorous species Would soon supply more food to several insects And probably to some terrestrial testacea So that the latter would gain ground The increase of these would furnish other insects and birds with food So that the numbers of these last would be augmented The diminution of the seals would afford a respite to some fish which they had persecuted And these fish in turn would then multiply and press upon their peculiar prey Many waterfowls, the eggs and young of which are devoured by foxes Would increase when the foxes were thinned down by the bears And the fish on which the waterfowls subsided would then in turn be less numerous Thus the numerical proportions of a great number of the inhabitants Both of the land and sea Might be permanently altered by the settling of one new species in the region And the changes caused indirectly would ramify through all classes of the living creation And be almost endless An actual illustration of what we have here only proposed hypothetically Is in some degree afforded by the selection of small islands by the either duck For its residents during the season of incubation Its nest being seldom, if ever found on the shores of the mainland Or even of a large island The Icelanders are so well aware of this that they have expanded a great deal of labour In forming artificial islands By separating from the mainland certain promontories joined to it by narrow ismuses This insular position is necessary to guard against the destruction of the eggs And young birds by foxes, dogs and other animals One year says Hooker It happened that in the small island of Vido Adjoining the coast of Iceland A fox got over upon the ice and caused great alarm As an immense number of ducks were then sitting on their eggs and young ones It was long before he was taken Which was at last however affected by bringing another fox to the island And fastening it by a string near the haunt of the former By which he was allured within shot of the hunter The first appearance of a new species causes the chief disturbance It is usually the first appearance of an animal or plant in a region to which it was previously a stranger That gives rise to the chief alteration Since after a time an equilibrium is again established But it must require ages before such an adjustment to the relative forces Of so many conflicting agents can be definitely settled The causes in simultaneous action are so numerous that they admit of an almost infinite number of combinations And it is necessary that all these should have occurred once before the total amount of change Capable of flowing from any new disturbing force can be estimated Thus for example suppose that once in two centuries a frost of unusual intensity Or a volcanic eruption of great violence accomplished by floods from the melting of glaciers Should occur in Iceland Or an epidemic disease fatal to the larger number of individuals of someone's species And not affecting others These and a variety of other contingencies All of which may occur at once Or at periods separated by different intervals of time Or to happen before it would be possible for us to declare what ultimate alteration The presence of any newcomer such as the bear before mentioned Might occasion in the animal population of the isle Every new condition in the state of the organic or inorganic creation A new animal or plant, an additional snow-clad mountain Any permanent change however slight in comparison to the whole Gives rise to a new order of things And may make a material change in regard to someone or more species Yet a swarm of locusts or a frost of extreme intensity Or an epidemic disease may pass away without any greater parent derangement No species may be lost And all may soon recover their former relative numbers Because the same scourges may have visited the region again and again In preceding periods Every plant that was incapable of resisting such a degree of cold Every animal which was exposed to be entirely cut off by an epidemic Or by famine caused by the consumption of vegetation by the locusts May have perished already So that the subsequent recurrence of similar catastrophes Is attended only by a temporary change Changes caused by man We are best acquainted with the mutations brought about by the progress of human population And the growth of plants and animals favoured by man To these therefore we should in the first instance turn our attention If we conclude from the concurrent testimony of history And of the evidence yielded by geological data That man is comparatively speaking of very modern origin We must at once perceive how great a revolution in the state of the animate world The increase of the human race Considered merely as consumers of a certain quantity of organic matter Must necessarily cause Whether man increases the productive powers of the earth It may perhaps be said that man has in some degree compensated For the appropriation to himself of so much food By artificially improving the natural productiveness of soils By irrigation, manure and adjudicious inter-mixture Of mineral ingredients conveyed from different localities But it admits of reasonable doubt Whether upon the whole we fertilize or impoverish the lands which we occupy This assertion may seem startling to many Because they are so much in the habit of regarding the sterility Or productiveness of land in relation to the wants of man And not as regards the organic world generally It is difficult at first to conceive if a morass is converted into arable land And made to yield a crop of grain even of moderate abundance That we have not improved the capabilities of the habitable surface That we have not empowered it to support a larger quantity of organic life In such cases, however, attract before of no utility to man May be reclaimed and become of high agricultural importance Though it may nevertheless yield a scantier vegetation If a lake be drained and turned into a meadow The space will provide sustenance to man And many terrestrial animals serviceable to him But not perhaps so much food as it previously yielded to the aquatic races If the pestiferous pontine marshes were drained and covered with corn Like the plains of the Po They might perhaps feed a smaller number of animals than they do now For these morasses are filled with herds of buffaloes and swine And they swarm with birds, reptiles and insects The felling of dense and lofty forests Which covered even within the records of history a considerable space on the globe Now tenanted by civilized men Must generally have lessened the amount of vegetable food Throughout the space where these woods grew We must also take into our account the area covered by towns And the still larger surface occupied by roads If we force the soil to bear extraordinary crops one year We are perhaps compelled to let a lie follow the next But nothing so much counterbalances the fertilizing effect of human art As the extensive cultivation of foreign herbs and shrubs Which although they are often more nutritious to man So don't thrive with the same rank luxuriance as the native plants of a district Man is in truth continually striving to diminish the natural diversity Of the stations of animals and plants in every country And to reduce them all to a small number fitted for species of economical use He may succeed perfectly in attaining his object Even though the vegetation be comparatively meager And the total amount of animal life be greatly lessened Spicks and maritas have given a lively description of the incredible number of insects Which lay waste to the crops of Brazil Besides swarms of monkeys, flocks of parrots and other birds As well as the paca gode and wild swine They describe the torment which the planter and naturalists suffer from the mosquitoes And the devastation of the ants and blittai They speak of the dangers to which they were exposed from the jaguar The poisonous serpents, crocodiles, scorpions, centipedes and spiders But with the increasing population and cultivation of the country Say these naturalists, these evils will gradually diminish When the inhabitants have cut down the woods And drained the marshes, made roads in all directions And founded villages and towns Man will, by degrees, triumph over the rank of vegetation and noxious animals And all the elements will second and amply recompense his activity The number of human beings now peopling the earth Is supposed to amount to 800 millions So that we may easily understand how great a number of beasts of prey, birds Animals of every class, this prodigious population must have displaced Independently of the still more important consequences Which have followed from the derangement brought about by man In the relative numerical strength of particular species Indigenous quadrupeds and birds extirpated in Great Britain Let us make some enquiries into the extent of the influence Which the progressive society has exerted during the last seven or eight centuries During the distribution of indigenous British animals Dr Fleming has prosecuted this enquiry with his usual zeal and ability And in a memoir on the subject has enumerated the best authenticated examples Of the decrease or extirpation of certain species during a period When our population has made the most rapid advances I shall offer a brief outline of his results The stag as well as the followed deer and the roe Were formally so abundant in our island that according to Leslie From 500 to 1000 were sometimes slain at a hunting match But the native races would already have been extinguished Had they not been carefully preserved in certain forests The otter, the martin and the pole cat were also in sufficient numbers To be pursued for the sake of their fur But they have now been reduced within very narrow bounds The wild cat and the fox have also been sacrificed throughout the greater part of the country For the security of the poultry yard or the fold Badgers have been expelled from every district which at former periods they inhabited Besides these which have been driven out from their favourite haunts And everywhere reduced in number there are some which have been wholly extirpated Such as the ancient breed of indigenous horses and the wild boar Of the wild oxen a few remains are still preserved in some of the old English parks The beaver which is eagerly sought after for its fur Had become scarce at the close of the 9th century And by the 12th century was only to be met with According to Gerardus de Bari in one river in Wales And another in Scotland The wolf once so much dreaded by our ancestors Is said to have maintained its ground in Ireland So late as the beginning of the 18th century 1710 Though it had been extirpated in Scotland 30 years before And in England at a much earlier period The bear which in Wales was regarded as a beast of the chase Equal to the hare or the boar Only perished as a native of Scotland in the year 1057 Many native birds of prey have also been the subjects of unremitting persecution The eagles, larger hawks and ravens have disappeared from the more cultivated districts The haunts of the mallard, the snipe, the red shank and the bittern Have been drained equally with the summer dwellings of the lapwig and the curlew But these species still linger in some portion of the British Isles Whereas the larger caper kelsies or wood grouse Formerly natives of the pine forests of Ireland and Scotland Have been destroyed within the last 60 years The egret and the crane which appear to have been formerly very common in Scotland Are now only occasional visitants The bustard, Otistada, observes graves In his British ornithology was formerly seen in the dawns and heaths of various parts of our island In flocks of 40 or 50 birds Whereas it is now a circumstance of rare occurrence to meet with a single individual Bewick also remarks that they were formerly more common in this island than at present They are now found only in the open counties of the south and east In the plates of Wiltshire, Dorsetshire and some parts of Yorkshire In the few years that have elapsed since Bewick wrote This bird has entirely disappeared from Wiltshire and Dorsetshire These changes it may be observed are derived from very imperfect memorials And relate only to the larger and more conspicuous animals inhabiting a small spot on the globe But they cannot fail to exalt our conception of the enormous revolutions which In the course of several thousand years the whole human species must have effected Extinction of the dodo The kangaroo and the emo are retreating rapidly before the progress of colonisation in Australia And it is scarcely admits of doubt that the general cultivation of that country Must lead to the extrepation of both The most striking example of the loss even within the last two centuries of a remarkable species Is that of the dodo A bird first seen by the Dutch when they landed on the Isle of France At that time uninhabited Immediately after the discovery of the passage to the East Indies by the Cape of Good Hope As of a large size and singular form Its wings short like those of an ostrich and wholly incapable of sustaining its heavy body Even for a short flight In its general appearance it differed from the ostrich, cassowary or any known bird Many naturalists gave figures of the dodo after the commencement of the 17th century And there is a painting of it in the British Museum Which is said to have been taken from a living individual Beneath the painting is a leg in a fine state of preservation Which all mythologists are agreed cannot belong to any other known bird In the museum at Oxford also there is a foot and a head in an imperfect state In spite of the most active search during the last century No information respecting the dodo was obtained And some authors have gone so far as to pretend that it never existed But a great mass of satisfactory evidence in favour of its recent existence Has now been collected by Mr Broderick And by Mr Strickland and Dr Melville Mr Strickland agreeing with Professor Reinhardt of Copenhagen In referring the dodo to the Columbia die calls it a vulture-like, frugivorous pigeon It appears also that another short-winged bird of the same order called the solitaire Inhabited the small island of Rodriguez 300 miles east of the Mauritius And has been exterminated by man, as have one or two different but ally birds of the Isle of Bourbon Rapid propagation of domestic quadrupeds over the American continent Next to the direct agency of man, his indirect influence in multiplying the numbers of large herbivorous quadrupeds of domesticated races May be regarded as one of the most obvious causes of the extermination of species On this and on several other grounds, the introduction of the horse, ox and other mammalia into America And their rapid propagation over that continent within the last three centuries Is a fact of great importance in natural history The extraordinary herds of wild cattle and horses which overran the plains of South America Sprung from a very few pairs first carried over by the Spaniards And they prove that the wide geographical range of large species in great continents Does not necessarily imply that they have existed there from remote periods Humbold observes in his travels on the authority of Azara That it is believed there exist in the Pampers of Buenos Aires 12 million cows and 3 million horses Without comprising in this enumeration the cattle that have no acknowledged proprietor In the Llanos of Caracas, the rich Hateros or proprietors of pastoral farms Are entirely ignorant of the number of cattle they possess The young are branded with the mark peculiar to each herd And some of the most wealthy owners mark as many as 14,000 a year In the northern plains from the Orinoco to the lake of Maraicabo Monsieur de Pons reckoned that 1,200,000 oxen, 180,000 horses and 90,000 mules Wanted at large In some parts of the valley of the Mississippi, especially in the country of the Osage Islands Wild horses are immensely numerous The establishment of black cattle in America dates from Columbus's second voyage to St. Domingo They there multiplied rapidly and that island presently became a kind of nursery From which these animals were successively transported to various parts of the continental coast And from thence into the interior Notwithstanding these numerous exportations In 27 years after the discovery of the island herds of 4,000 head As we learn from Oviedo were not uncommon And there were even some that amounted to 8,000 In 1587 the number of hides exported from St. Domingo alone According to Acosta's report was 35,444 And in the same year they were exported 64,350 from the ports of New Spain This was in the 65th year after the taking of Mexico Previous to which event the Spaniards who came into that country Had not been able to engage in anything else than war Everyone is aware that these animals are now established throughout the American continent From Canada to the Straits of Magellan The ass has thriven very generally in the New World And we learn from Ulloa that in Quito they ran wild and multiplied in amazing numbers So as to become a nuisance They graced together in herds and when attacked defended themselves with their mouths If a horse happened to stray into the place where they fed They all fell upon him and did not cease biting and kicking till they left him dead The first hogs were carried to America by Columbus And established in the island of St. Domingo the year following its discovery In November 1493 In succeeding years they were introduced into other places where the Spaniards settled And in the space of half a century they were found established in the New World From the latitude of 25 degrees north to the 40th degree of south latitude Sheep also and goats were multiplied enormously in the New World As have also the cat and the rat Which last as before stated has been imported unintentionally in ships The dogs introduced by man which have at different periods become wild in America Hunted in packs like the wolf and the jackal destroying not only hogs But the calves and foals of the wild cattle and horses Ulloa in his voyage and before on the authority of old writers Relate a fact which illustrates very clearly the principle before explained Of the check which the increase of one animal necessarily offers to that of another The Spaniards had introduced goats into the island of Juan Fernández They became so prolific as to furnish the pirates who infested these seas with provisions In order to cut off this resource from the buccaneers A number of dogs were turned loose into the island And so numerous that they become in their turn That they destroyed the goats in every accessible part After which the number of wild dogs again decreased Increase of reindeer imported into Iceland As an example of the rapidity with which a large tract may become people By the offspring of a single pair of quadrupeds It may be mentioned that in the year 1773 Thirteen reindeer were exported from Norway Only three of which reached Iceland These were turned loose into the mountains of Goldbridge-Sissel Where they multiplied so greatly in the course of forty years That it was not uncommon to meet with herds Consisting of from forty to one hundred in various districts The reindeer observes a modern writer Is in Lapland a loser by his connection with man But Iceland will be this creature's paradise There is in the interior a tract which Sergei Mackenzie Computes at not less than forty thousand square miles Without a single human habitation And almost entirely unknown to the natives themselves There are no wolves The Icelanders will keep out the bears And the reindeer being almost unmolested by man Will have no enemy whatever Unless it has brought with it its own tormenting gadfly Besides the quadrupeds before enumerated Our domestic foals have also succeeded in the West Indies and America Where they have the commonfall The goose The duck The pigeon And the guinea fall As these were often taken suddenly from the temperate To very hot regions They were not reared at first without much difficulty But after a few generations They became familiarized to the climate Which in many cases Approached much nearer than that of Europe To the temperature of their original native countries The fact of so many millions of wild and tamed individuals Of our domestic species Almost all of them the largest quadrupeds and birds Having been propagated throughout the new continent Within the short period that has elapsed Since the discovery of America While no appreciable improvement can have been made In the productive powers of that vast continent Affords abundant evidence of the extraordinary changes Which accompany the diffusion and progressive advancement Of the human race over the globe That it should have remained for us To witness such mighty revolutions Proof even if there was no other evidence That the entrance of man into the planet Is comparatively speaking of extremely modern date And that the effects of his agency Are only beginning to be felt Population which the globe is capable of supporting A modern writer has estimated That there are in America Upwards of four million square miles of useful soil Each capable of supporting two hundred persons And nearly six million each mile capable of supporting Four hundred and ninety persons If this conjecture be true It will follow as that author observes That if the natural resources of America Were fully developed it would afford sustenance To five times as greater number of inhabitants As the entire mass of human beings Existing at present upon the globe The new continent he thinks Though less than half the size of the old Contains an equal quantity of useful soil And much more than an equal amount of productive power Be this as it may we may safely conclude That the amount of human population now existing Constitutes but a small proportion Of that which the globe is capable of supporting Or which it is destined to sustain At no distant period by the rapid progress of society Especially in America, Australia And certain parts of the old continent Power of exterminating species But if we reflect that many millions Of square miles of the most fertile land Occupied originally by a boundless variety Of animal and vegetable forms Have been already brought under the dominion Of man and compelled in a great measure To yield nourishment to him And to a limited number of plants and animals Which he has caused to increase We must at once be convinced That the annihilation of a multitude Of species has already been effected And will continue to go on hereafter In certain regions in a still more rapid ratio As the colonies of highly civilized nations Spread themselves over unoccupied lands Yet if we wield the sword of extermination As we advance we have no reason to repine At the havoc committed nor to fancy With the Scottish poet that we violate The social union of nature Or complain with the melancholy sharks That we are mere usurpers, tyrants And what's worse to fright the animals And to kill them up In their assigned and native dwelling place We have only to reflect that In thus obtaining possession of the earth By conquest and defending our acquisitions By force we exercise no exclusive prerogative Every species which has spread itself From a small point over a wide area Must in like manner have marked its progress By the diminution or the entire Extrepation of some other And must maintain its ground By a successful struggle against The encroachment of other plants and animals That minute parasitic plant Called the rust in wheat Has like the Hessian fly The locust and the aphids Caused famines ear now Amongst the lords of the creation The most insignificant and diminutive species Whether in the animal or vegetable kingdom Have each slaughtered their thousands As they disseminated themselves over the globe As well as the lion When first it spread itself Over the tropical regions of Africa Concluding remarks Although we have as yet considered One class only of the causes The organic by which species May become exterminated Yet it cannot but appear evident That the continued action of these alone Throughout myriads of future ages Must work an entire change In the state of the organic creation Not merely on the continents On the continents and islands Where the power of man is chiefly exerted But in the great ocean Where his control is almost unknown The mind is prepared by the contemplation Of such future revolutions To look for the signs of others Of an analogous nature In the monuments of the past Instead of being astonished At the proofs there manifested Of endless mutations in the animate world They will appear to one who has thought Profoundly of the fluctuations Will progress to afford evidence In favour of the uniformity of the system Unless indeed we are precluded From speaking of uniformity When we characterise a principle Of endless variation And of Chapter 41 Recording by Sycamore Rockwell www.voinofvoiceovers.com Chapter 42 Part 1 Of Principles of Geology This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer Please visit LibriVox.org Recording by Avahi in March 2018 Principles of Geology By Charles Lyle Chapter 42 Extinction of Species Influence of Inorganic Causes Part 1 Powers of diffusion indispensable That each species may maintain its ground How changes in physical geography Affect the distribution of species Rate of the change of species Due to this cause cannot be uniform Every change in the physical geography Of large regions tends to the extinction of species Effects of a general alteration of climate On the migration of species Gradual refrigeration would cause species In the northern and southern hemispheres To become distinct Elevation of temperature the reverse Effects on the condition of species Which must result from inorganic changes Inconsistent with the theory of transmutation Powers of diffusion indispensable That each species may maintain its ground Having shown in the last chapter How considerably the numerical increase Or the extension of the geographical range Of any one species Must arrange the numbers and distribution of others Let us now direct our attention to the influence Which the inorganic causes described in the second book Are continually exerting on the habitations of species So great is the instability of the earth's surface That if nature were not continually engaged In the task of sowing seeds and colonizing animals The deep population of a certain portion Of the habitable sea and land Would in a few years be considerable Whenever a river transports sediment Into a lake or sea So as materially to diminish its depth The aquatic animals and plants Which delight in deep water are expelled The tract, however, is not allowed to remain useless But is soon peopled by species Which require more light and heat And thrive where the water is shallow Every addition made to the land By the encroachment of the delta of a river Banishes many sub-aqueous species From their native abodes But the new formed plain is not permitted To lie unoccupied, being instantly covered With terrestrial vegetation The ocean devours continuous lines of sea coasts And precipitates forests or rich pasture land Into the waves But this space is not lost to the animate creation For shells and seaweeds Soon adhere to the new-made cliffs And numerous fish people the channel Which the current has scooped out for itself No sooner has a volcanic island Been thrown up that some lichens Begin to grow upon it And it is sometimes clothed with vajur While smoke and ashes are still occasionally thrown From the crater The cocoa, pandanus and mangrove Take root upon the coral reef Before it has fairly risen above the waters The burning stream of lava that descends from Etna Rolls through the stately forest And converts to ashes every tree and herb Which stands in its way But the black strip of land thus desolated Is covered again in the course of time With oaks, pines and chestnuts As luxuriant as those which the fiery torrent swept away Every flood and landslip Every wave which a hurricane or earthquake Throws upon the shore Every shower of volcanic dust and ashes Which buries a country far and wide To the depth of many feet Every advance of the sand flood Every conversion of salt water into fresh When rivers alter their main channel of discharge Every permanent variation in the rise Or fall of tides in an estuary These and countless other causes displace In the course of a few centuries Certain plants and animals from stations Which they previously occupied If, therefore, the author of Nature Had not been prodigal to those numerous contrivances Before alluded to For spreading all classes of organic beings Over the earth If he had not ordained that the fluctuations Of the animate and inanimate creation Should be in perfect harmony with each other It is evident that considerable spaces Now the most habitable on the globe Would soon be as devoid of life As are the alpine snows Or the dark abysses of the ocean Or the moving sands of the Sahara The powers then of migration and diffusion Conferred on animals and plants Are indispensable to enable them to maintain their ground And would be necessary Even though it were never intended That a species should gradually extend Its geographical range But a facility of shifting their quarters Being once given It cannot fail to happen that the inhabitants Of one province should occasionally Penetrate into some other Since the strongest of those barriers Which I before described As separating distinct regions Are all liable to be thrown down One after the other During the vicissitudes of the earth's surface How changes in physical geography Affect the distribution of species The numbers and distribution Of particular species are affected in two ways By changes in the physical geography of the earth First, these changes promote Or retard the migrations of species Secondly, they alter the physical conditions Of the localities which species inhabit If the ocean should gradually wear its way Through an Isthmus, like that of Suez It would open a passage for the intermixture Of the aquatic tribes of two seas Previously disjoint And at the same time close a free communication Which the terrestrial plants and animals Of two continents had before enjoyed These would be, perhaps, The most important consequences In regard to the distribution of species Which would result from the breach Made by the sea in such a spot But there would be others of a distinct nature Such as the conversion of a certain tract of land Which formed the Isthmus into sea This space previously occupied By terrestrial plants and animals Would be immediately delivered over to the aquatic A local revolution which might have happened In innumerable other parts of the globe Without being attended by any alteration In the blending together of species Of two distinct provinces Rate of change of species cannot be uniform This observation leads me to point out One of the most interesting conclusions To which we are led by the contemplation Of the vicissitudes of the inanimate world In relation to those of the animate It is clear that if the agency Of inorganic causes be uniform, as I have Supposed, they must operate very irregularly On the state of organic beings So that the rate according to which these Will change in particular regions Will not be equal in equal periods of time I am not about to advocate the doctrine Of general catastrophes recurring at certain intervals As in the ancient oriental cosmogenes Nor do I doubt that if very considerable Periods of equal duration could be compared One with another, the rate of change In the living as well as in the inorganic World might be nearly uniform But if we regard each of the causes separately Which we know to be at present Most instrumental in remodeling the state of the surface We shall find that we must expect each to be In action for thousands of years Without producing any extensive alterations In the habitable surface and then to give rise During a very brief period to important revolutions Illustration derived from substances I shall illustrate this principle by a few Of the most remarkable examples which present Themselves In the course of the last century as we have seen A considerable number of instances are recorded Of the solid surface, whether covered by water Or not, having been permanently sunk Or upraised by subterranean movements Most of these convulsions are only accompanied By temporary fluctuations in the state Of limited districts and a continued repetition Of these events for thousands of years Might not produce any decided change in the state Of many of those great zoological or botanical provinces Of which I have sketched the boundaries When, for example, large parts of the ocean And even of inland seas are a thousand fathoms Or upwards in depth, it is a matter of no moment To the animate creation that vast tracts Should be heaved up many fathoms at certain intervals Or should subside to the same amount Neither can any material revolution be produced In South America, either in the terrestrial Or the marine plants or animals, by a series Of shocks on the coast of Chile, each of which Like that of Pencor in 1751 Should uplift the coast about 25 feet Nor if the ground sinks 50 feet at a time As in the harbor of Port Royal in Jamaica In 1692, will such alterations of level Work any general fluctuations in the state Of organic beings inhabiting the West Indian Islands or the Caribbean Sea? It is only when the subterranean powers By shifting gradually the points where Their principal forces developed happen To strike upon some particular region Where a slight change of level immediately Infects the distribution of land and water Or the state of the climate or the barriers Between distinct groups of species over Extensive areas that the rate of fluctuation Becomes accelerated and may, in the course Of a few years or centuries, work mightier Changes than had been experienced in myriads Of antecedent years. Thus, for example, a repetition of Incidences causing the narrow isthmus of Panama to sink down a few hundred feet Would, in a few centuries, bring about A great revolution in the state of the Animate creation in the western hemisphere. Thousands of aquatic species would pass For the first time from the Caribbean Sea into the Pacific, and thousands of Others, before peculiar to the Pacific Ocean, would make their way into the Caribbean Sea, the Gulf of Mexico, and the Atlantic. A considerable modification would probably Be occasioned by the same event in the Direction or volume of the Gulf stream, And thereby the temperature of the sea And the contiguous lands may be altered As far as the influence of that current Extends. A change of climate might thus be Produced in the ocean from Florida To Spitzbergen, and in many countries America, Europe, and Greenland. Not merely the heat, but the quantity Of rain which falls would be altered In certain districts, so that many Species would be excluded from tracts Where they before flourished, others Would be reduced in number, and some Would thrive more and multiply. The seeds also and the fruits of Plants would no longer be drifted In precisely the same directions, nor The eggs of aquatic animals. Neither would species be any longer Impeded in their migrations Towards particular stations before Shut out from them by their inability To cross the mighty current. Let us take another example from a Part of the globe which is at present Liable to suffer by earthquakes, Namely, the low sandy tract which Intervenes between the Sea of Azoth And a Caspian. If there should occur a sinking Down to a trifling amount, and such Revenes should be formed, this might Be produced by a few earthquakes, Not more considerable than have fallen Within our limited observation During the last 150 years, the waters Of the Sea of Azoth would pour rapidly Into the Caspian, which, according To the measurements lately made by The Academy of St. Petersburg, is 84 feet below the level of the Black Sea. The Sea of Azoth would immediately Borrow from the Black Sea, that sea Again from the Mediterranean and The Mediterranean from the Atlantic, So that an inexhaustible current Would pour down into the low Tracts of Asia bordering the Caspian, By which all the sandy salt steps Adjacent to that sea would be Inundated. An area of several thousand Square leagues, now below the Level of the Mediterranean, would Be converted from land into sea. Illustration derived from the Elevation of land. Let us next imagine a few cases Of the Elevation of land of small Extent at certain critical points, As, for example, in the shallowest Part of the Straits of Gibraltar, Where the deepest soundings from The African to the European side Give only 220 fathoms. In proportion, as this Submarine barrier of rock was Peaved, the whole channel would Be contracted in width and Depth, and the volume of water Which the current constantly flowing From the Atlantic pours into The Mediterranean would be lessened. But the loss of the inland sea By evaporation would remain the Same, so that being no longer Able to draw on the ocean for A supply sufficient to restore Its equilibrium, it must sink And leave dry a certain portion Of land around its borders. The current which now flows Constantly out of the black sea Into the Mediterranean would then Rush in more rapidly, and the Level of the Mediterranean would Be thereby prevented from Falling so low, but the level Of the black sea would, for the Same reason, sink, so that when By a continued series of Elevatory movements the Straits Of Gibraltar had become Completely closed up, we might Expect large and level sandy Steps to surround both the Black sea and Mediterranean Like those occurring at present Under skirts of the Caspian And the lake of Oral. The geographical range of Hundreds of aquatic species Would be thereby circumcised And that of hundreds of Terrestrial plants and animals Extended. A line of Submarine volcanoes crossing The channel of some straight Choking it up with ashes and lava Might produce a new barrier As effectively as a series Of earthquakes, especially If thermal springs charged With carbonate of lime, silica And other mineral ingredients Should promote the rapid Multiplication of corals and Shells, and cement them Together with solid matter Precipitated during the Intervals between eruptions. Suppose in this manner a Changed to be caused of the Bahama Channel between the bank of that Name and the coast of Florida. This insignificant revolution Confined to a mere spot In the bottom of the ocean Would, by diverting the Main current of the Gulfstream Give rise to extensive changes In the climate and distribution Of animals and plants inhabiting The northern hemisphere. Illustration from the formation Of new islands. A repetition of Elevatory movements of earthquakes Might continue over an area As extensive as Europe For thousands of ages At the bottom of the ocean In certain regions, and produce No visible effects. Whereas, if they should operate In some shallow parts of the Pacific Amid the coral archipelagos They would soon give birth To a new continent. Hundreds of volcanic islands And become covered with vegetation Without causing more than Local fluctuations in the animate World. But if a chain Like the Allusion Archipelago Or the Curial Isles Run for a distance of many Hundred miles, so as to form An almost uninterrupted communication Between two continents Or two distant islands The migration of plants, Birds, insects and even Of some quadrupeds may cause In a short term An extraordinary series of revolutions Tending to augment the range Of some animals and plants And to limit that of others. A new archipelago Might be formed in the Mediterranean, The Bay of Biscay And a thousand other places And might produce less important Events than one rock Which should rise up between Australia And Java, so placed That winds and currents might cause An interchange of the plants, Insects and birds From the wearing through of an Isthmus If we turn from the igneous To the aqueous agents, We find the same tendency To an irregular rate of change Naturally connected with the strictest Uniformity in the energy Of those causes. When the sea, for example, Gradually encroaches upon both Sides of a narrow Isthmus Of Sleswick, separating the North Sea from the Baltic, Where, as before stated, The cliffs on both the opposite coasts Are wasting away, No material alteration results For thousands of years, Save only that there is a progressive Conversion of a small strip of land Into water. A few feet only, Or a few yards, are annually removed, But if, at last, The partition should be broken down And the tides of the ocean Should enter by a direct passage Into the inland sea, Instead of going by a circuitous Route through the catagate, A body of salt water would sweep Up as far as the gulfs of Bothnia and Finland, The waters of which are now brackish Or almost fresh, And this revolution would be attended By the local annihilation Of many species. Similar consequences Must have resulted on a small scale When the sea opened its way Through the Isthmus of Stavaren In the 13th century, Forming a union between an inland lake And the ocean, And opening, in the course of one century, A shallow strait, More than half as wide as the narrowest Part of that which divides England from France. Changes in physical geography Which must occasion extinction of species. It will almost seem superfluous After I have thus traced The important modifications In the condition of living beings Which flow from changes of trifling Extent, to argue that Entire revolutions might be brought About if the climate And physical geography of the whole Globe were greatly altered. It has been stated That species are in general local, Some being confined to extremely Small spots, and depending For their existence on a combination Of causes, which, if they are To be met with elsewhere, Occur only in some very Remote region. Hence it must happen that When the nature of these localities Is changed, the species will perish, For it will really happen That the cause which alters The character of the district Will afford new facilities to the Species to establish itself Elsewhere. End of chapter 42 part 1