 6. A new estimate of the temperature of Mars. When we are presented with a complex problem, depending on a great number of imperfectly ascertained data, we may often check the results thus obtained with the comparison of cases which in some of the more important of these data are identical, while others are at a maximum or a minimum. In the present case, we can only do this by a consideration of the Moon as compared with the Earth and with Mars. 5. Langley's Determination of the Moon's Temperature. In the Moon, we see conditions that prevail in Mars both exaggerated and simplified. While this is a very scanty atmosphere, the Moon none at all, but if there is one, it is so excessively scanty that the most refined observations have not detected it. All the complications arising from the possible nature of the atmosphere and its complex effects upon reflection, absorption, and radiation are thus eliminated. The mean distance of the Moon from the Sun being identical with that of the Earth, the total amount of heat its accepted must also be identical. Only in this case, the whole of it reaches the surface instead of one fourth only according to Mr. Lowell's estimate for the Earth. Now, by the most refined observations with his volometer, Mr. Langley was able to determine the temperature of the Moon's surface exposed to undimmed sunshine for 14 days altogether, and he found that even in the portion of it on which the Sun was shining almost vertically, the temperature rarely rose above the freezing point of water. However extraordinary this result may seem, it is really a striking confirmation of the accuracy of the general laws determining temperature with eye of endeavor to explain in the preceding chapter. For the same surface, which has had 14 days of sunshine, has also had preceding 14 days of darkness during which the heat which it had accumulated in its surface layers would have been lost by free radiation into stellar space. It thus acquires during its day a maximum temperature of only 491 degrees Fahrenheit absolute. While its minimum after 14 days of continuous radiation must be very low and is with much reason supposed to approach the absolute zero. Rapid loss of heat by radiation on the Earth. In order better to comprehend what this minimum may be under extreme conditions, it will be useful to take note of the effects it already produces on the Earth in places where the conditions are nearest to those existing on the Moon or on Mars, who are never quite equaling or even approaching very near them. It is in our great desert regions and especially on high plateau that extreme humidity prevails, and it is in such districts that the differences between day and night temperatures reach their maximum. It is stated by geographers that in parts of the Great Sahara the surface temperature is sometimes 150 degrees Fahrenheit, while during the night it falls nearly or quite to the freezing point, a difference of 118 degrees in little more than 12 hours. In the high desert plains of Central Asia, the extremes are said to be even greater. Again, in his universal geography, reckless states that in the Armenian highlands the thermometer oscillates between 13 degrees Fahrenheit and 112 degrees Fahrenheit. We may therefore, without any fear of exaggeration, take it as proved that a fall of 100 degrees Fahrenheit in 12 or 15 hours not unfrequently occurs where there is a very dry and clear atmosphere, permitting continuous installation by day and rapid radiation by night. Now, as it is admitted that odd dense atmosphere, however dry and clear, absorbs and reflects some considerable portion of the solar heat, we shall certainly underestimate the radiation from the moon's surface during its long night if we take as a basis of our calculation a lowering of temperature amounting to 100 degrees Fahrenheit during 12 hours as not unfrequently occurs with us. Using these data with step-and-slaw decrease of radiation at the fourth power of the temperature, a mathematical friend finds it the temperature of the moon's surface will be reduced during the lunar night to nearly 200 degrees Fahrenheit absolute, equal to minus 258 degrees Fahrenheit. More rapid loss of heat by the moon, although such a calculation as the above may afford us a good approximation to the rate of loss of heat by Mars with this very scanty atmosphere. We have now good evidence that in the case of the moon the losses much more rapid. Two independent workers have investigated the subject with very accordant results. Dr. Boddika with Lord Roshy's three-foot reflector and a thermopile to measure the heat, and Mr. Frank Berry with a glass reflector of 12 inches in diameter and the volometer invented by Mr. Langley. The very striking and unexpected fact in which these observers agree is the sudden disappearance of much of the sort of heat during the comparatively short duration of a total eclipse of the moon. Less than two hours of complete darkness in about twice that period of partial obscuration. Dr. Boddika was unable to detect any appreciable heat at the period of great sub-scaration but owing to the extreme sensitiveness of the volometer, Mr. Berry ascertained that those parts of the surface which had been longest in shadow still emitted heat to the amount of one percent of the heat to be expected from a full moon. This, however, is the amount of radiation registered by the volometer, and to get the temperature of the radiating surface we must apply Steppen's law of the fourth power. Hence the temperature of the moon's dark surface will be the fourth root of one over one hundred equivalent to one over three point two of the highest temperature, which would be take at the freezing point of 491 degrees Fahrenheit absolute or 154 degrees Fahrenheit absolute, just below the liquefaction point of air. This is about 50 degrees lower than the amount found by calculation for emotional rapid radiation, and this amount is produced in a few hours. It is not too much to expect it would continue for more than two weeks, the lunar night, it might reach a temperature sufficient to liquefy hydrogen, 60 degrees Fahrenheit absolute, or perhaps even below it. Theory of the moon's origin. This extremely rapid loss of heat by radiation at first sight, so improbable as to be almost incredible, may perhaps be to some extent explained by the physical constitution of the moon's surface, which from a theoretical point of view does not appear to have received the attention it deserves. It is clear that our satellite has long been subjected to volcanic eruptions over its whole visible face, and these have evidently been of an explosive nature, so as to build up the very lofty cones and craters, well as thousands of smaller ones which, owing to the absence of benedigrating or denuding agencies, have remained piled up as they were first formed. This highly volcanic structure can, I think, be well explained by an origin such as that attributed to it by Sir George Darwin, and which has been so well described by Sir Robert Ball in this small volume of time and tide. These astronomers do strong evidence that the Earth once rotated so rapidly that the equatorial protuberance was almost at the point of separation from the planet as a ring. Before this occurred, however, the tension was so great that one large portion of the protuberance, where it was weakest, broke away and began to move around the Earth at some considerable distance from it. As about one-fiftieth of the bulk of the Earth thus escaped, it must have consisted of a considerable portion of the solid crust and a much larger quantity of the liquid or semi-liquid interior, together with a proportionate amount of the gases which we know formed and still form an important part of the Earth's substance. As the surface layers of the Earth must have been the lightest, they would necessarily, when broken up by the gigantic convulsion, have come together to form the exterior of the new satellite, and soon be adjusted by the forces of gravity and tidal disturbance into a more or less irregular spheroidal form, all of whose interstices and cavities would be filled up and connected together by the liquid or semi-liquid mass forced up between them. Thence forward, as the Moon increased its distance and reduced its time of rotation in the way explained by Sir Robert Ball, there would necessarily commence a process of escape of the imprisoned gases at every fissure and at all points in lines of weakness, giving rise to numerous volcanic outlets, which, being subjected only to the small force of lunar gravity, only one-sixth that of the Earth, would, in the course of ages, pile up those gigantic cones and ridges which form its great characteristic. With this small gravitated power of the Moon would prevent its retaining on its surface any of the gases forming our atmosphere, which would all escape from it and probably be recaptured by the Earth. By no process of external aggregation of solid matter to such a relatively small amount as that forming the Moon, even if the aggregation was so violent as to produce heated up to cause liquefaction, could any such long continued volcanic action arise by gradual cooling in the absence of internal gases? There might be fissures and even some outflows of molten rock, but without imprisoned gases and especially without water and water vapor producing explosive outbursts, could any such amount of scoriae and ashes be produced as were necessary for building up of the vast volcanic cones, craters and cratoliths we see upon the Moon's surface? I'm not aware that either Sir Robert Ball or Sir George Darwin have reduced this highly volcanic condition to the Moon's surface as a phenomenon which can only be explained by our satellite having been thrown off by a much larger body whose gravitative force was sufficient to acquire and retain the enormous quantity of gases and of water which we possess and which are absolutely essential for that special form of cone building volcanic action which the Moon exhibits in so preeminent a degree. Yet it seems clear to me that some such hypothetical origin for our satellite would have had to be assumed if Sir George Darwin had not deduced it by means of purely mathematical argument based upon astronomical facts. Returning now to the problem of the Moon's temperature, I think the phenomena this presents may be in part due to the mode of formation here described. For its entire surface being the result of long continued gaseous explosions, all the volcanic products, scoriae, pumice and ashes would necessarily be highly porous throughout and never having been compacted by water action as on the earth and there having been no winds to carry the finer dust so as to fill up their porous and fissures, the whole of the surface material to a very considerable depth must be loose and porous to a high degree. This condition has been further increased owing to the small power of gravity and the extreme irregularity of the surface consisting very largely of lofty cones and ridges very loosely piled up to enormous heights. Now this condition of the substances of the Moon's surface is such as would produce a high specific heat so that it would absorb a large amount of heat in proportion to the rise of the temperature produced, the heat being conducted downwards to a considerable depth. Owing however to the total absence of atmosphere radiation would very rapidly cool the surface but afterwards more slowly both on account of the action of Steppen's law and because the heat stored up in the deeper portions could be carried to the surface by conduction only and with extreme slowness. Various researches on the Moon's heat. The results of the eclipse observations are supported by the detailed examination of the surface temperature of the Moon by Mr. Vary in his prize essay on the distribution of the Moon's heat published by the Utrecht Society of Arts and Sciences in 1891. He shows by a diagram on the phase curve that at the commencement of the lunar day the surface just within the illuminated limb has acquired about one seventh of its maximum temperature or about 70 degrees Fahrenheit absolute. As the surface exposed to the palometer at each observation is about one 30th of the Moon's surface and in order to ensure accuracy the instrument has to be directed at a spot lying wholly within the edge of the Moon. It is evident that the surface measured has already been for several hours exposed to a bleak sunshine. The curve of the temperature then rises gradually and afterwards more rapidly. Chile detains its maximum of about positive 30 to 40 degrees Fahrenheit a few hours before noon. This Mr. Vary thinks is due to the fact that half the Moon's face first illuminated porous has on the average a darker surface than that of the afternoon or second quarter during which the curve descends not quite so rapidly. The temperature near sunset being only a little higher than that near sunrise. This rapid fall while exposed to a bleak sunshine is quite in harmony with the rapid loss of heat during the few hours of darkness during an eclipse both showing the pre-potency of radiation over insulation on the Moon. Two other diagrams show the distribution of heat at the time of full Moon. One half of the curve showing the temperatures along the equator from the edge to the disc of the center. The other along a meridian from this center to the pole. This diagram here reproduced exhibits the quick rise of temperature of the bleak rim of the Moon and the nearly uniform heat of the central half of its surface. The diminishing of heat towards the pole, however, is slower for the first half and more rapid for the latter portion. It is an interesting fact that the temperature near the margin of the full Moon increases towards the center more rapidly than it does when the same parts are observed during the early phases of the first quarter. Mr. Vary explains this difference as being due to the fact that the full Moon to its very edges is fully illuminated, all of the shadows of the ridges and mountains being thrown vertically or obliquely behind them. We thus measure the heat reflected from the whole visible surface. But at new Moon and somewhat beyond the first quarter, the deep shadows thrown by the smallest combs and ridges, as well as loftiest mountains, cover a considerable portion of the visible surface, thus largely reducing the quantity of light and heat reflected or radiated in our direction. It is only at the full, therefore, that the maximum temperature of the whole lunar surface can be measured. It must be considered a proof for the delicacy of the heat-measuring instruments that this difference in the curves of temperature of the different parts of the Moon's surface and other different conditions is so clearly shown. The application of the preceding results to the case of Mars. This somewhat lengthy account of the actual state of the Moon's surface and temperatures are very great importance in our present inquiry, because it shows us the extraordinary differences in mean and extreme temperature of two bodies situated at the same distance from the Sun, and therefore receiving exactly the same amount of solar heat per unit of surface. We've learned also what are the main causes of this almost incredible difference, namely one. A remarkably rugged surface with porous and probably cavernous rock texture, leading to an extremely rapid radiation of heat in the one, as compared with the comparatively even and well-compacted surface largely clung with vegetation, leading to a comparatively slow and gradual loss by radiation in the other, and two. These results being greatly intensified by the total absence of a protecting atmosphere on the former, while a dense and cloudy atmosphere with an ever-present supply of water vapor accumulates and equalizes the heat received by the latter. The only other essential difference in the two bodies, which may possibly aid in the production of this marvelous result, is the fact of odd day and night having a mean length of twelve hours, while those of the Moon are about fourteen and a half of odd days. But the altogether unexpected fact, in which two independent inquirers agree, that during the few hours duration of a total eclipse of the Moon, so large a portion of the heat is lost by radiation renders it almost certain that the resulting low temperature would be not very much less if the Moon had a day and night the same length as our own. The great lesson we learned by this extreme contrast of conditions supplied to us by nature as if to enable us to solve some of her problems is the overwhelming importance first of a dense and well-compacted surface, due to water action and strong gravitative force, secondly of a more or less general coat of vegetation, and thirdly of a dense vapor laden atmosphere. These three favorable conditions result in a mean temperature of about 60 degrees Fahrenheit, with a range seldom exceeding 40 degrees above or below. While over more than half of the land surface of the earth, the temperature rarely falls below the freezing point. On the other hand, we have a globe with the same materials and at the same distance from the Sun with the maximum temperature of freezing water in a minimum not very far from the absolute zero. The monthly mean being probably much below the freezing point of carbonic acid gas, a difference entirely due to the absence of these three favorable conditions, the special features of Mars as influencing temperature. Coming now to the special feature of Mars in its probable temperature, we find that most writers have arrived at a very different conclusion from that of Mr. Lowell, who himself quotes Mr. Moulton as an authority, who recently by the application of Stefan's law has found the mean temperature of this planet to be minus 35 degrees Fahrenheit. Again, Professor J. H. Pointy, in his lecture on radiation in the solar system delivered before the British Association of Cambridge in 1904, gave an estimate of the mean temperature of the planets arrived at from measurements of the Sun's emissive power and the application of Stefan's law to the distances of the several planets, and he thus finds the Earth to have a mean temperature of 17 degrees centigrade and Mars to have one of minus 38 degrees centigrade. A wonderfully close approximation to the mean temperature of the Earth is determined by direct measurement, and therefore, presumably, an equally near approximation to that of Mars as dependent on the distance from the Sun and on the supposition that it is Earth-like in all its conditions. What we know that it is far from being Earth-like in the very conditions which we have found to be those which determine the extremely different temperatures of the Earth and the Moon, and in regards to each of these, we find that so far as it is different from the Earth, it approximates to the less favorable conditions that prevail in the Moon. The first of these conditions which we have found to be essential in regulating the absorption and radiation of heat and thus raising the mean temperature of a planet is a compact surface well covered with vegetation. Two conditions are rising from and absolutely dependent on an ample amount of water. But Mr. Lowell himself assures us as a fact which he has no doubt there are no permanent bodies of water great or small upon Mars that rain and consequently rivers are totally wanting, that its sky is almost constantly clear, and that what appear to be clouds are not formed of water vapor but of dust, he dwells emphatically on the terrible desert conditions of the greater part of the surface of the planet. That being the case now, we have the right to assume that it is ever been otherwise, and taking into full account of the fact neither denied nor dissuaded by Mr. Lowell, that the force of gravity on Mars is not sufficient to retain water vapor in its atmosphere, we must conclude that the surface of the planet like that of the Moon has been molded by some form of volcanic action modified probably by wind but not by water. Adding to this that the force of gravity on Mars is nearer that of the Moon than that of the Earth, we may reasonably conclude that its surface is formed of volcanic matter and a light porous condition and therefore highly favorable for the rapid loss of surface heat by radiation. The surface conditions of Mars are therefore presumably much more like those of the Moon than those of the Earth. The next condition favorable to the storing of a peat, a covering of vegetation is almost certainly absent from Mars except possibly over limited areas for short periods. In this feature also the surface of Mars approximates much nearer to the lunar than to Earth conditions. The third condition a dense vapor laden atmosphere is also wanting in Mars for although it possesses an atmosphere it is estimated by Mr. Lowell in his latest article to have a pressure equivalent to only two and a half inches of mercury with us giving it a density of only one 12 part that of ours. While aqueous vapor the cheap accumulator of heat cannot permanently exist in it and notwithstanding repeated spectroscopic observations for the purpose of detecting it has never been proved to exist. I submit that I have now shown from the statements and largely as a result of the long continued observations of Mr. Lowell himself that so far as the physical conditions of Mars are known to differ from those of Earth the differences are all unfavorable to the conservation and favorable to the dissipation of the scanty heat it receives from the Sun that they point unmistakably toward the temperatures conditions of the Moon rather than to those of the Earth and that the cumulative effect of these adverse conditions acting upon a heat supply reduced by solar distance to less than one half of ours must result in a mean temperature as well as in the extremes near to that of our satellite than to that of our own Earth. Further criticism of Mr. Lowell's article we are now in a position to test some further conclusions of Mr. Lowell's philosophical magazine article by comparison with actual phenomena. We have seen in the outline I have given in this article that the endeavors to show how the small amount of solar heat received by Mars is counterbalanced largely by the greater transferase to light and heat of its thin and cloudless atmosphere and partially also by a greater conservative or blanketing power of its atmosphere due to the presence in it of a large proportion of carbonic acid gas and aqueous vapor. The first of these statements may be admitted as a fact which is entitled to dwell upon but the second the presence of large quantities of carbon dioxide and aqueous vapor is a pure hypothesis unsupported by any item of scientific evidence. Following the case of aqueous vapor it is directly opposed to admitted results founded upon the molecular theory of gaseous elasticity but although Mr. Lowell refers to the conservative or blanketing effect of the Earth's atmosphere he does not consider or allow for its very great cumulative effect that is strikingly shown by the comparison with the actual temperature conditions of the moon. This cumulative effect is due to the continuous reflection and radiation of heat from the clouds as well as from the vapor latent strata of air in our lower atmosphere which later though very transparent to the luminous and accompanying heat rays of the sun is opaque to the dark heat rays with a radiated reflective from the Earth's surface. We are therefore in a position strictly comparable with that of the interior of some huge glass house which not only becomes intensely heated by the direct rays of the sun but also to a less degree by reflected rays from the sky and those radiated from the clouds so that even on a cloudy or misty day its temperature rises many degrees above that of the outer air. Such a building if of large size of suitable form and well protected at night by blinds or other covering might be so arranged as to accumulate heat in its soil and walls as to maintain a tolerably uniform temperature though exposed to a considerable range of external heat and cold. It is to such a power of accumulation of heat in our soil in lower atmosphere that we must impute the overwhelming contrast between our climate and that of the moon. With us the solar heat that penetrates our vapor latent and cloudy atmosphere is shot in by that same atmosphere accumulates there for weeks and months together and can only slowly escape. It is this great cumulative power which Mr. Loa has not taken account of. While he certainly has not estimated the enormous loss of heat by free radiation which entirely neutralizes the effects of increase of sun heat however great when these cumulative agencies are not present. See footnote 12. Temperature on polar regions of Mars. There is also a further consideration which I think Mr. Loa has altogether omitted to discuss. Whatever may be the mean temperature of Mars we must take account of the long nights in its polar and high temperate latitudes lasting nearly twice as long as ours. With the resulted lowering of temperature by radiation into a constantly clear sky even in Siberia in latitude 67 and a half degrees north a cold of minus 88 degrees Fahrenheit has been attained. While over a large portion of North Asia and America above 60 degrees latitude the mean January temperature is from minus 30 degrees Fahrenheit to minus 60 degrees Fahrenheit and the whole subsoil is permanently frozen to a depth of six or seven feet to several hundreds but the winter temperature over the same latitude in Mars must be very much lower and it must require a proportionate large amount of its feeble sun heat to raise the temperature even to the freezing point and an additional very large amount to melt any considerable depth of snow but this identical area a little below 60 degrees to the pole is that occupied by the snow caps of Mars and over the whole of it the winter temperature must be far lower than the earth minimum of minus 88 degrees Fahrenheit then as the Martian summer comes on there's less than half the sun heat available to raise the slow temperature after winter nearly doubled the length of ours and when the summer does come with its scanty sun heat that heat is not accumulated as it is by our dense and moisture laden atmosphere the marvelous effects of which we have already shown yet with all these adverse conditions each assisting the other to produce a climate approximating to that which the earth would have if it had no atmosphere but retaining our superiority over Mars and receiving double the amount of sun heat we are asked to accept a mean temperature for the more distant planet almost exactly the same as that of mild and equitable southern england and the disappearance of the vast snow fields of its polar regions as rapid and complete as what occurs with us if the moon even at its equator had not its temperature raised above the freezing point of water how can the more distant Mars with its oblique noonday sun falling upon the snow caps receive heat enough first to raise the temperature to 32 degrees Fahrenheit and then to melt with marked rapidity the vast frozen plains of its polar regions mr. Lowell is however so regardless of the ordinary teachings of meteorological science that he actually accounts for the supposed mild climate to the polar regions of Mars by the absence of water on its surface and in its atmosphere he concludes in his fifth chapter with the following words could our earth but get rid of its oceans we too might have temperate regions stretching to the poles here he runs counter to two of the best established laws of terrestrial climatology the wonderful equalizing effects of warm ocean currents which are the chief agents in diminishing polar cold the equally striking effects of warm moist winds derived from these oceans and the great storehouse of heat we possess in our vapor-laden atmosphere its vapor being primarily derived from these same oceans but in mr. Lowell's opinion all our meteorologists are quite mistaken our oceans are our great drawbacks only get rid of them and we should enjoy the exquisite climate of Mars with its absence of clouds and fog of rains or rivers and its delightful expenses of perennial desert buried towards a pole by a scenty snowfall in winter the melting of which might with great care supply us with the necessary moisture to grow wheat and cabbages for about one tenth or more likely one hundredth of our present population i hope i may be excused for not treating such an argument seriously the various considerations now advanced especially those of which show the enormous cumulative and conservative perspective are dense and water-related atmosphere and the disastrous effect judging from the actual condition of moon which the loss of it would have upon our temperature seem to be quite sufficient to demonstrate important errors in the data or fallacies in the complex mathematical argument by which mr. Lowell has attempted to uphold his views as the temperature and consequent climactic conditions of Mars in concluding this portion of my discussion of the problem of Mars i wish to call attention to the fact that my arguments founded upon a comparison that the physical conditions of the earth and moon with those of Mars is dependent on a small number of generally admitted scientific facts are the conclusions strong from those facts are simple and direct require no mathematical knowledge to follow them or to appreciate their weight and cogency i claim for them therefore that they are no degree speculative but in their data and methods exclusively scientific in the next chapter i'll put forth a suggestion as to how the very curious markings upon the surface of Mars may possibly be interpreted so as to be in harmony with the planet's actual physical condition and it's not improbable origin and past history footnote 10 keith johnson's africa and stanford's compendium footnote 11 chambers encyclopedia article on deserts footnote 12 the effects of this cumulative power of a dense atmosphere are further discussed and illustrated in the last chapter of this book where i show that the universal fact of steadily diminishing temperatures at higher altitudes is due solely to the diminishing of this cumulative power of our atmosphere and that from this cause alone the temperatures of Mars must be at that which would be found on lofty plateau about 18 000 feet higher than the average peaks of the andes this concludes chapter six chapter seven of is mars habitable this is a liber box recording all liber box recordings are in the public domain for more information or to volunteer please visit liberbox.org is mars habitable by alfred russell mollus chapter seven a suggestion as to the canals of Mars the special characteristics of the numerous lines which intersect the hold of the equatorial and temperate regions of Mars are their straightness combined with their enormous length it is this which has led mr. Lowell to turn them non-natural features chaparelli in his earlier drawings show them curved in a comparatively great width later he found them to be straight fine lines when seen under the best conditions but as mr. Lowell has always seen them in the pure atmosphere of his observatory both of these observers were first doubtful of their reality the persistent observation continued at many successive oppositions compelled acceptance of the misactual features of the planet's disk so many other observers have now seen them that the objection of their unreality seems no longer valid mr. Lowell urges however that their perfect straightness and their extreme tenuity of their uniformity throughout their whole length the dual character of many of them their relation to the oases and the form and position of these round black spots are all proofs of artificiality and are suggestive of design and considering that some of them are actually as long as from Boston to San Francisco and relatively to their globe as long as from London to Bombay his objection that no natural phenomena within our knowledge shows such regularity on such a scale seems at first a mighty one it is certainly true that we can point to nothing exactly like them either on the earth or on the moon but these are the only two planetary bodies we are in a position to compare with Mars yet even these do I think afford us some hints toward the interpretation of the mysterious lines but as our knowledge of the internal structure and past history even of our earth is still imperfect that of the moon only conjectural and that of Mars a perfect blank it is not perhaps surprising that the surface features of the latter do not correspond with those of either of the others Mr. Pickering's suggestion the best clue to a natural interpretation the strange features of the surface of Mars is that suggested by the American astronomer Mr. W. H. Pickering in popular astronomy 1904 briefly it is that both the canals of Mars and the rifts as well as luminous streaks on the moon are cracks in the volcanic crust caused by internal stresses due to the action of the heated interior these cracks he considers to be symmetrically arranged with regard to small cratoliths Mr. Lowell's oases because they have originated from them just as the white streaks on the moon radiate from the larger craters as centers he further supposes that water and carbon dioxide issue from the interior into these fissures and in conjunction with sunlight promote the growth of vegetation owing to a very rare atmosphere the vapor ceasings would not ascend roll down the outside to the cratoliths and along the borders of the canals thus irrigating the immediate vicinity and serving to promote the growth of some form of vegetation which renders the canals and oases visible see footnote 13 this opinion is especially important because next to Mr. Lowell Mr. Pickering is perhaps the astronomer who has given the most attention to Mars during the last 15 years he was for some time at Flagstaff with Mr. Lowell and it was he who discovered the oases or cratoliths and who originated the idea that we did not see the canals themselves but only the vegetable growth on their borders he's also observed Mars in the southern hemisphere at Araquipa and he has since made an elaborate study of the moon by means of a specially constructed telescope of 135 feet focal length which produced a direct image on photographic plates nearly 16 inches in diameter see footnote 14 it is clear therefore that Mr. Lowell's views as the artificial nature of the canals are not accepted by an astronomer of equal knowledge and still wider experience yet Professor Pickering's alternative view is more a suggestion than an explanation because there is no attempt to account for the enormous length and the perfect straightness of the lines on Mars so different from anything that is found either on our earth or on the moon there must be evidently some great peculiarity of structure or of conditions on Mars to account for these features and I shall now attempt to point out what the peculiarity is and how it may have arisen the meteoric hypothesis during the last quarter of a century a considerable change has come over the opinions of astronomers regards to the probable origin of the solar system the large amount of knowledge of the stellar universe and especially of Nebula of comets and meteor streams which we now possess together with many other phenomena such as the constitution of Saturn's rings with a great number and extended the minor planets and generally of the vast amount of matter in the form of meteor rings and meteoric dust in and around our system have all pointed to a different origin for the planets and their satellites and that formulated by Laplace as the nebular hypothesis it is now seen more clearly than at any earlier period that most of the planets possess special characteristics which distinguish them one from another and that such an origin as Laplace suggested the slow cooling and contraction of one that's Sunnist or Nebula besides presenting inherent difficulties many think of them in possibilities in itself does not afford an adequate explanation of these peculiarities hence has origin what is termed the meteoric theory which has been ably advocated for many years by Sir Norman Lockyer and with some important modifications is now becoming widely accepted briefly this theory is that the planets have been formed by the slow aggregation of solid particles around centers of greatest condensation but as many of my readers may altogether be unaquated with it I will here give a very clear statement of what is from Professor J. W. Gwegeri's presidential address to the geological section of the British Association of the present year he began by saying that these modern views were far more practical to use of men of science than that of Laplace and that they give us a history of the world consistent with the actual records of geology he then continues according to Sir Norman Lockyer's meteoric hypothesis nebulae comets and many so-called stars consist of forms of meteorites which though normally cold and dark are heated by repeated collisions and become so luminous they may even be volatilized into glowing meteoric vapor but in time this heat is dissipated and the force of gravity condenses a meteoric swarm into a single globe some of the swarms are says Lockyer truly members of the solar system and some of these travel round the sun in nearly circular orbits like planets they may be regarded as infinitesimal planets and so Chamberlain calls him planetesimals the planetesimal theory is a development of the meteoric theory and presents it in an especially attractive guise it regards meteorites as very sparsely distributed through space and gravity as powerless to collect them into dense groups so it assigns the parentage of the solar system to a spiral nebula composed of planetesimals and the planets as formed from nuts in the nebula where many planetesimals had been concentrated near the intersection of their orbits these groups of meteorites already densest swarm of bees were then packed closer by the influence of gravity and the contracting mass was heated by the pressure even above the normal melting point of the material which was kept rigid by the weight of the overlying layers now adopting this theory is the last word of science upon the subject of the origin of planets we see that it affords immense scope for diversity and results depending on the total amount of matter available within the range of attraction of an incipient planetary mass and the rates at which this matter becomes available by a special combination of these two quantities which have almost certainly been different for each planet i think we may be able to throw some light upon the structure and the physical features of Mars the probable mode of origin for Mars this planet lying between two of much greater mass has evidently had less material from which to be formed by aggregation and if we assume as in the absence of evidence to the contrary we have a right to do that its beginnings were not much later or earlier than those of the earth then its smaller size shows that it has in all probability aggregated very much more slowly but the internal heat acquired by a planet while forming in this matter will depend upon the rate at which it aggregates and the velocity with which the planet decimals fall into it and this velocity will increase with its mass and consequent forces of gravity in the early stages of a planet's growth it will probably remain cold then a small amount of heat produced by each impact being lost by radiation before the next one occurs and with a small and slowly aggregating planet this condition will prevail till it approaches its full size then only will its gravitated force be sufficient to cause incoming matter to fall upon it with so powerful an impact as to reduce intense heat further the compressive force of a small planet will be a less effective heat producing agency than in the case of a larger one the earth we know has acquired a large amount of internal heat probably sufficient to liquefy its whole interior but Mars has only one ninth part the mass of the earth and it is quite possible and even probable it is competitively small attractive force would never have liquefied or even permanently heated the more central portions of its mass this being admitted i suggest the following course of events as being quite possible and not even improbable in the case of this planet during the whole of its early growth until it acquired nearly its present diameter its rate of aggregation was so slow that the planet decimals falling upon it that they might have been heated and even partially liquefied by the impact were never in any such quantity as to lose any considerable heating effect on the whole mass and each local rise of temperature was soon lost by radiation the planet thus grew as a solid and cold mass compacted together by the impact of incoming matter as well as by its slowly increasing gravitative force but when it had attained to within perhaps 100 perhaps 50 miles or less of its present diameter a great change occurred in the opportunity for further growth some large and dense swarm of meteorites perhaps containing a number of bodies of the size of the asteroids came within the range of the sun's attraction and were drawn by it into an orbit which crossed that of Mars at such a small angle that the planet was able at each revolution to capture a considerable number of them the result might then be that as in the case of the earth the continuous in pour of the fresh matter first heated and later on liquefied the greater part of it as well perhaps as a thin layer of the planet's original surface so that when in due course the whole of the meteor swarm had been captured Mars had acquired its present mass but would consist of an intensely heated and either liquid or plastic thin outer shell resting upon a cold and solid interior the size and position of the two recently discovered satellites of Mars which are believed to be not more than 10 miles in diameter the more remote revolving around its primary very little slower than the planet rotates while the nearer one which is considerably less distant from the planet's surface than its own antipodes and revolves around it more than three times during the Martian day may perhaps be looked upon as the remnants of the great meteor swarm which completed the Martian development and which are perhaps themselves destined at some distant period to fall into the planet should future astronomers witness a phenomenon the effect produced upon its surface would be full of instruction as the result of such an origin as that suggested Mars would possess a structure which in the essential feature of heat distribution would be the very opposite of that which is believed to characterize the earth yet it might have been produced by a very slight modification of the same process this peculiar heat distribution together with a much smaller mass and gravitative force would lead to a very different development of the surface and an altogether diverse geological history from ours which has throughout been profoundly influenced by its heated interior its vast supply of water and the continuous physical and chemical reactions between the interior and the crust these reactions have in our case been of substantially the same nature and very nearly of the same degree of intensity throughout the whole vast eons of geological time and they have resulted in a wonderfully complex succession of rock formations volcanic, plutonic and sedimentary more or less intermingled throughout the whole series here remaining horizontal as when first deposited they're upheaved or depressed fractured or crushed inclined or contorted denuded by rain and rivers with the assistance of heat and cold of frost and ice in an unceasing series of changes so however very the surface may be with hill and dale plains and uplands mountain ranges and deep intervening valleys these are as nothing to the diversities of the interior structure as exhibited in the sides of every alpine valley or precipitous escarpment and made known to us by the work of the miner and the well borer in every part of the world structural straight lines on the earth the great characteristic of the earth both on its surface and in its interior is thus seen to be extreme diversity both of form and structure and this is further intensified by the very texture constitution hardness and density of the various rocks and debris of which it is composed it is therefore not surprising that with such a complex outer crust we should nowhere find examples of these geometrical forms and almost worldwide straight lines that give us such remarkable and as mr. Lowell maintains non-natural character of the surface of Mars but which as seems to be of themselves afford prima facie evidence of a corresponding simplicity and uniformity in its internal structure yet we are not ourselves by any means devoid of straight lines structurally produced in spite of every obstacle the diversity of form and texture of softness and hardness of lamination or crystallization which are adverse to such developments examples of these are the numerous faults which occur in the harder rocks and which often extend for great distances in almost perfect straight lines in our own country we have the tinnicide and craven faults in the north of england which are 30 miles long in often 20 yards wide but even more striking is the great gleeblen dyke a wall of volcanic rock dipping slightly towards the south but sometimes being almost vertical and stretching across the country over hill and dale in almost perfect straight lines from a point on the coast 10 miles north of scarborough in a west by north direction passing about two miles south of stockton and terminating about six miles north by east of barnard castle a distance of very nearly 60 miles the great fault between the highlands and the lowlands of scotland extends across the country from stone haven to new helensberg a distance of 120 miles and there are very many more of less important much more extensive are some of the great continental dislocations and often forming valleys of considerable width and length the upper rine flows in one of these great valleys of sightings for about 180 miles from mule housing to frankfort in a generally straight line though modified by denudation vasta still is the valley of the jordan to the sea of galilee to the dead sea continued by way of the wadi araba to the gulf of akaba relieved to form one vast geological depression or fracture extending in a straight line for 400 miles thousands of such faults dykes or depressions exist in every part of the world all believed to be due to the gradual shrinking of the heated interior to which the solid crust has to accommodate itself and they are especially interesting and instructive for our present purposes and showing the tendency of such fractures of solid rock material to extend to great lengths in straight lines notwithstanding the extreme irregularity both of the surface contour as well as in the internal structures of the very deposits and formations through which they pass probable origin of the surface features of mars returning now to mars let us consider the probable course of events from the point at which we left it the heat produced by impact and condensation would be likely to release gases which had been in combination with some of the solid matter or perhaps then itself in a solid state due to the intense cold and these escaping outwards to the surface would produce on a small scale a certain amount of upheaval and volcanic disturbance is in an outer crust rapidly formed a number of events might remain as craters or cratoliths in a moderate state of activity owing to the comparatively small force of gravity the outer crust would become scouracious and more or less permeated by the gases which would continue to escape through it and this would facilitate the cooling of the whole of the heated outer crust and allow it to become rather densely compacted when the greater portion of the gases had thus escaped into the outer surface and assisted to form a scanty atmosphere such as now exists there would be no more internal disturbance and the cooling of the heated outer coating would steadily progress resulting at last in a slightly heated and later in a cold layer of moderate thickness and great general uniformity owing to the absence of rain and rivers denudation such as we experience would be unknown though the superficial scouracious crust might be partially broken up by expansion and contraction and suffer a certain amount of atmospheric erosion the final result of this mode of aggregation would be that the planet would consist of an outer layer of moderate thicknesses compared with the central mass which the outer layer would have cooled from a highly heated state to a temperature considerably below the freezing point and this would have all the time been contracting upon a previously cold and therefore non-contracting nucleus the result would be that very early in the process great superficial tensions would be produced which would only be relieved by cracks of fissures which would initiate at points of weakness probably at the crater that's already referred to from which they would radiate in several directions each crack thus formed near the surface would as cooling progressed develop in length and depth and owing to the general uniformity of the material and possibly some amount of crystalline structure due to slow and continuous cooling down to a very low temperature the cracks would tend to run on in straight lines and to extend vertically downwards which two circumstances would necessarily result in their forming portions of great circles on the planet's surface the two great facts which mr. Lowell appeals to as being especially non-natural symmetry of basaltic columns we have however one quite natural fact on our earth which serves to illustrate one of these two features the direction of the downward fissure this is the comparatively common phenomena of basaltic commons and in the giant's causeways the wonderful regularity of these and especially the not-unfrequent upright pillars in serried ranks as in the palisades of the Hudson River must have always impressed observers with their appearance of artificiality yet they are undoubtedly the result of very slow cooling and contraction of melted rocks under compression by strata below and above them so that when once solidified the mass was held in position and the tension produced by the contraction could only be relieved by numerous very small cracks and short distances from each other in every direction resulting in five six or seven sided polygons with sides only a few inches long this contraction began of course at the coolest surface generally the upper one an observation of these columns in various positions has established the rule that the direction length ways is always at right angles to the cooling surface and thus whenever the surface was horizontal the columnists became almost exactly vertical how this applies to Mars one of the features of the surface of Mars that Mr. Lowell describes with much confidence is that it is wonderfully uniform and level which of course it would be if it had once been in liquid or plastic state not much disturbed since by volcanic or other internal movements the result would be the cracks formed by the contraction of the hardened outer crust would be vertical and in a generally uniform material at a very uniform temperature these cracks would continue almost indefinitely in straight line the hardened and contracting surface being free to move laterally on account of there being a more heated and plastic layer below it the cracks once initiated above were continually widened at the surface as they penetrated deeper and deeper into the slightly heated substratum now as the salt begins to soften at about 1400 degrees Fahrenheit and the surface of Mars has cooled to at least the freezing point perhaps very much below it the contraction would be so great that if the fishes produced were 500 miles apart they might be three miles wide at the surface and if only 100 miles apart then about two-thirds of a mile wide see footnote 15 but as the production of the fishes might have occupied perhaps millions of years a considerable amount of atmospheric denudation would result however slowly it acted the expansion and contracted would wear away the edges and the sides of the fishes fill up many of them with the debris and widen them at the surfaces to perhaps double their original size see footnote 16 suggested explanation of the oases the numerous round dots seen upon the canals and especially at points from which several canals radiate and where they intersect termed oases by mr. Lowell and craterlets by mr. Pinkering may be explained in two ways those from which several canals radiate may be true craters from which the gasses imprisoned in the heated surface layers have gradually escaped they would be situated at points of weakness in the crust and become centers for which cracks would start during contraction those dots which occur at the crossing of two straight canals or cracks may have originated from that that at such intersections there would be four sharply projecting angles which being exposed to the influence of alternate heat and cold during day and night on the two opposite surfaces would inevitably in time become fractured and crumbled away resulting in the formation of a roughly circular chasm which would become partly filled up by the debris those formed by cracks radiating from craterlets would also be subject to the same process of rounding off to an even greater extent and thus would be produced the oases of various sizes up to 50 miles or more in diameter recorded by mr. Lowell and other observers probable function of the great fishes mr. Pinkering as we have seen supposes that these fishes give out the gasses which overflowing on each side favor the growth of the supposed vegetation which renders the course of the canals visible and this no doubt may have been the case during remote periods when these cracks gave access to the heated portions of the surface layer but it seems more probable that Mars has now cooled down to the almost uniform mean temperature it derives from solar heat and that the fishes now for the most part broad shallow valleys serve mealy as channels along which the liquids and heavy gases derived from the melting of this solar snows naturally flow and owing to their nearly level surfaces over flow to a certain distance on each side of them suggested origin of the blue patches these heavy gases mainly perhaps as has often been suggested carbon dioxide would when in large quantity and of considerable depth reflect a good deal of light and being almost inevitably dust laden might produce that blue change adhesion to the melting snow caps with mr. Lowell has erroneously assumed to be itself a proof of the presence of liquid water just as the blue of our sky is undoubtedly due to the reflection from the ultra minute dust particles in our higher atmosphere similar particles brought down by the snow from the higher martian atmosphere might produce the blue tinge in the great volumes of heavy gas produced by its evaporation or liquefaction it may be noted that mr. Lowell objects to the carbon dioxide theory of the formation of the snow caps that this gas at low pressure does not liquefy but passes it once from the solid to the gaseous state and that only water remains liquid sufficiently long to produce the blue color which plays a larger part in his argument for the mild climate essential for an inhabited planet with this argument as i have already shown is valueless for only very deep water can possibly show a blue color by reflected light while the dust laden atmosphere especially with a layer of very dense gas at the bottom of it this would be the case with the newly evaporated carbon dioxide from the diminishing snow cap which provide the very conditions likely to produce this blue tinge of color it may be considered a support to this view the carbonic acid gas becomes a liquid at minus 140 degrees fahrenheit and solid at minus 162 degrees fahrenheit temperatures far higher than what you'd expect to reveal in the polar and north temperate regions of mars during a considerable part of the year but such as might be reached there during the summer solstice when the snow so rapidly disappeared to be reformed a few months later the double canals the curious phenomena of the double canals are undoubtedly the most difficult to explain satisfactorily on any theory which has yet been suggested they vary in distance apart from about 100 to 400 miles and in many cases they appear perfectly parallel and mr. Lowell gives us the impression that they are almost always so but his map show in some cases decided differences from width at the two extremities indicating considerable want to parallelism a few of the curved canals are also double there is one drawing in mr. Lowell's book on page 219 on the mouse or starting points of the Euphrates and Phyton two widely separated double canals diverging at an angle of about 40 degrees from the same two oases so that the two inner canals cross each other now this suggests two bands of weakness in the planet's crust radiating probably from within the dark tract called the Marae Incarium and that some widespread volcanic outbursts initiated diverging cracks on either side of these bands something of this kind may have been this cause of the most of the double canals or they may have been started from two or more cratoliths not far apart the direction being at first decided by some local peculiarity of structure and where begun continuing in straight lines owing to the homogeneity or uniform density of the material this is very vague but the phenomena are so remarkable and so imperfectly known at present that nothing but suggestion can be attempted concluding remarks on the canals in this somewhat detailed exposition of a possible and i hope a probable explanation the surface features of Mars i have endeavored to be guided by known facts or accepted theories both astronomical and geological i think i may claim to have shown that there are some analogous features of terrestrial rock structure to serve as guides towards a natural and intelligible explanation of the strange geometric markings discovered during the last 30 years and which have raised this planet from comparative obscurity into position of the very first rank within astronomical and popular interest this widespread interest is very largely due to mr. Lowell's devotion to its study within seeking out so admirable a position as regards altitude and climate and establishing there a first class observatory it also in bringing his discoveries before the public in connection with the theory so startling as to compel attention i venture to think that his merit is one of our first astronomical observers will in no way be diminished by the rejection of his theory and the substitution of one or more in accordance with the actually observed facts footnote 13 nature volume 70 page 536 footnote 14 nature volume 70 may fifth page 11 supplement footnote 15 the coefficient of contraction of the salt is 6 times 10 to the minus 6th for each one degree Fahrenheit which would lead to the results given here footnote 16 mr. wh pickering observed clouds on mars 15 miles high is a projection seen on the terminator when the planet is partially illuminated they were at first thought to be mountains but during the opposition of 1894 more than 400 of them were seen at flagstaff during nine months observation usually they are rare occurrence they're seen to change in form and position from day to day and mr. Lowell is strongly of the opinion that they are dust storms not what we term clouds they were mostly about 13 miles high indicating considerable aerial disturbances on the planet and therefore capable of producing proportional surface denudation appendix a suggested experiment to illustrate the canals of mars if my explanation of the canal should be substantially correct that is if they were produced by the contraction of a heated outward crust upon a cold and therefore non-contracting interior the result of such a condition might be shown experimentally several baked clay balls might be formed to serve as cores save eight to ten inches in diameter these being fixed within molds of say half an inch to an integrator diameter the outer layer would be formed by pouring some suitably heated liquid material and releasing it from the mold as soon as consolidation occurs so that it may cool rapidly from the outside some kinds of impure glass or the brittle metals bismuth or antimony or alloys of these might be used in order to see what form the resulting fractures would take be well to have several duplicates of each ball and as soon as tension through contraction manifests itself to try the effect of spiring very small charges a small shot to ascertain whether such impacts would start radiating fractures when taken from the molds the ball should be suspended in a slight current of air and kept rotating to reproduce the planetary condition as nearly as possible the exact size and material of the cores the thickness of the heated outer crust and the material best suited to show fracture by contraction and the details of the treatment might be modified in various ways as to suggest the results first obtained such a series of experiments would probably throw further light upon the physical conditions which have produced the gigantic system of fissures or canals we see upon the surface of mars though would not of course prove that such conditions actually existed there in such a speculative matter we could only be guided by probabilities based upon whatever evidence is available this concludes chapter seven chapter eight of is mars habitable this is a livervox recording all livervox recordings are in the public domain for more information or to volunteer please visit livervox.org is mars habitable by albert russell wallace chapter eight summary and conclusion this little volume has necessarily touched upon a great variety of subjects in order to deal in a tolerably complete manner with a very extraordinary theaters by which mr. Lowell attempts to explain the unique features of the surface of the planet which by long continued study he has almost made his own it may therefore be well to sum up the main points of the arguments against his view introducing a few other facts and considerations which greatly strengthen my argument the one great feature of mars which led mr. Lowell to adopt the view of its being inhabited by a race of highly intelligent beings and with ever-increasing discovery to uphold the theory to the present time is undoubtedly that of the so called canals their straightness their enormous length their great abundance and their extension over the planet's whole surface from one polar snowcap to the other the very immensity of the system and its constant growth in extension during 15 years of persistent observation have so completely taken possession of his mind that after a very hasty glance at analogous facts and possibilities he has declared them to be non-natural therefore to be works of art therefore to necessitate the presence of highly intelligent beings who have designed and constructed them this idea has colored or governed all his writings on the subject the innumerable difficulties which it raises have been either ignored or brushed aside on the flimsiest evidence as examples he never even discusses the totally inadequate water supply for such worldwide irrigation or the extreme irrationality of constructing so vast a canal system the waste from which by evaporation when exposed to such desert conditions as he himself described would use up 10 times the probable supply again he urges the purpose displayed in these canals they're being all so straight all describing great circles of the sphere all being so evidently arranged as he thinks either to carry water to some oasis 2,000 miles away or to reach some arid region far over the equator in the opposite hemisphere but he never considers the difficulties as implies everywhere these canals run for thousands of miles across waterless deserts forming a system and indicating a purpose the wonderful perfection of which he is never tired of dwelling upon but which i myself can nowhere perceive yet he never even attempts to explain how the Martians could have lived before this great system was planned and executed or why they did not first utilize and render fertile the belt of land adjacent to the limits of the polar snows why the method of irrigation did not as with human arts begin gradually at home with terraces and channels to irrigate the land close to the source of the water how with such a desert he describes three fourths of mars to be did the inhabitants ever get to know anything of the equatorial regions and its needs to start right away to supply those needs all this to my mind is quite opposed to the idea of there being works of art and altogether in favor of there being natural structures of a globe as peculiar in origin and internal structure as it is in the surface features the explanation i have given course hypothetical is found unknown cosmical and terrestrial fact and is i suggest far more scientific as well as more satisfactory than mr. Lowell's wholly unsupported speculation this view i have explained in some detail in the preceding chapter mr. Lowell never even refers to the important question of lost by evaporation in these enormous open canals or considers the undoubted fact that the only intelligent and practical way to convey a limited quantity of water such great distances would be by a system of watertight and airtight tubes laid under the ground the mere attempt to use open canals for such a purpose shows a complete ignorance and stupidity in these alleged very superior beings while it is certain that long before half of them were completed their failure to be of any use would have led any rational beings to cease constructing them he also fails to consider the difficulty that if these canals are necessary for the existence of mars how did the inhabitants ever reach a sufficiently large population with surplus food and leisure enabling them to rise with a low condition of savages to one of civilization and ultimately to scientific knowledge here again is a dilemma which is hard to overcome only a dense population with ample means of subsistence could possibly have constructed such gigantic works but given these two conditions no adequate motive existed for the conception and execution of them even if they were likely to be of any use which i have shown they could not be further considerations on the climate of mars recurring now to the question of climate which is all important mr. Lowell never even discusses the essential point the temperature that must necessarily result from an atmospheric envelope one twelfth or at most one seventh the density of our own in either case corresponding to an altitude far greater than that of our highest mountains see footnote 17 surely this phenomenon everywhere manifested on earth even under the equator of a regular decrease of temperature with altitude the only cause of which is a less dense atmosphere should have been fairly grappled with and some attempt made to show why it should not apply to mars except the weak remark that on a level surface it does not have the same effect as on exposed mountain heights but it does have the same effect or very nearly so on our lofty plateau often hundreds of miles in extent in proportion to their altitude keto at 9350 feet above the sea has a mean temperature of about 57 degrees fahrenheit giving a lowering of 23 degrees from that of monos at the mouth of the rayon agro this is about a degree for each 400 feet what the general fall for isolated mountains is about one degree in 340 feet according to humboldt who notes the above differences between the rate of cooling for altitude of the plains or more usually sheltered valleys in which the towns are situated and the exposed mountain sides it will be seen that this lower rate would bring the temperature of mars at the equator down to 20 degrees fahrenheit below the freezing point of water from this cause alone but all inquirers have admitted that if conditions as to the atmosphere where the same is on the earth its greater distance from the sun will reduce the temperature to minus 31 degrees fahrenheit equal to 63 degrees below the freezing point it is therefore certain that the combined defective bulb causes must bring the temperature of mars down to at least 70 or 80 degrees below the freezing point the cause of this absolute dependence of terrestrial temperatures upon density the air envelope is seldom discussed in textbooks either of geography or of physics and there seems to be still some uncertainty about it some imputed holy to the thinner air being unable to absorb and retain so much heat as that which is more dense but if this were the case the soil at great altitude not having so much of its heat taken up by the air should be warmer than below since it undoubtedly receives more heat owing to the greater transparency of the air above it but it certainly does not become warmer the more correct view seems to be that the loss of heat by radiation has increased so much through the rarity of the air above it as to more than counterbalance the increased insulation so that the surface of the earth at a given altitude may receive 10 percent more direct sun heat it loses by direct radiation combined with diminished air and cloud radiation perhaps 20 or 25 percent more when there is a resultant cooling effect of 10 or 15 percent this acts by day as well as by night so that the greater heat received at high altitudes does not warm the soil as much as a less amount of heat with a denser atmosphere this effect is further intensified by the fact that the less dense cannot absorb and transmit so much heat as a more dense atmosphere here then we have an absolute law of nature to be observed operating everywhere on the earth and the mode of action which is fairly well understood this law is that reduced atmospheric pressure increases radiation or loss of heat more rapidly than it increases insulation or gain of heat so that the result is always a considerable lowering of temperature what this lowering is can be seen in the universal fact that even within the tropics perpetual snow covers a higher mountain summits while on the high plains of the Andes at 15 000 or 16 000 feet altitude where there's very little or no snow travelers are often frozen to death when delayed by storms yet at this elevation the atmosphere has much more than double the density of that of Mars the error in Mr Lowell's argument is that he claims for the scanty atmosphere of Mars that allows more sun heat to reach the surface that he admits to take account of the enormously increased loss of heat by direct radiation as well as the diminution of air radiation which together necessarily produces a great reduction of temperature it is a great principle the prepotency of radiation over absorption with the diminishing atmosphere that explains the excessively low temperatures of the moon's surface a fact which also serves to indicate a very low temperature for Mars as i have shown in chapter six these two independent arguments from alpine temperatures and from those of the moon support and enforce each other and afford a conclusive proof that against anything advanced by Mr Lowell that the temperature of Mars must be far too low to support animal life a third independent argument leading to the same result as dr johnstone stony's proof that aqueous favor cannot exist on Mars and this fact Mr Lowell does not even attempt to controvert to put the whole case in the fewest possible words one all physicists are agreed that owing to the distance of Mars from the sun it would have a mean temperature of about minus 35 degrees fahrenheit equivalent to 456 degrees fahrenheit absolute even if it had an atmosphere as dense as ours two but the very low temperatures on earth under the equator had a height with a varometer stands at about three times as high as on Mars proves that from the scantiness of the atmosphere alone Mars cannot possibly have a temperature as high as the freezing point of water and this proof is supported by Langley's determination of the low maximum temperature of the full moon the combination of these two results must bring down the temperature of Mars to a degree wholly incompatible with the existence of animal life three the quite independent proof that water vapor cannot exist in Mars and that therefore the first essential of organic life water is non-existent the conclusion from these three independent proofs which enforce each other in a multiple ratio their respective weights is therefore irresistible that animal life especially in its higher forms cannot exist on the planet Mars therefore is not only uninhabited by intelligent beings such as Mr Lowell postulates but is absolutely uninhabitable footnote 17 a four inches varometer is equivalent to a height of 40 000 feet above the sea level with us this concludes chapter eight and marks the conclusion of is Mars habitable