20 the ecliptic, is not the sole cause of climatic variations on the surface of the globe. High altitude and the existence of oceanic and aerial currents, carrying and diffusing the heat of the equatorial region to the other parts of the globe, have been found to produce different climates in countries having the same latitude. The Gulf Stream is a notable instance of such oceanic currents and had it not been for this stream the climate in the North-West of Europe would have been quite different from what it is at present. Again if the masses of land and water be differently distributed from what they are at present, there is every reason to suppose that different climatic conditions will prevail on the surface of the globe from those which we now experience, as such a distribution would materially alter the course of oceanic and aerial currents going from the equator to the Poles. Therefore, in the early geological ages, when the Alps were low and the Himalayas not yet upheaved and when Asia and Africa were represented only by a group of islands we need not be surprised if, from geological evidence of fossil fauna and flora, we find that an equable and uniform climate prevailed over the whole surface of the globe as the result of these geographical conditions. In Mesozoic and Cainozoic times this state of things appears to have gradually changed. But though the climate in the Secondary and the Tertiary era was not probably as remarkably uniform as in the Primary, yet there is clear geological evidence to show that until the close of the Pliocene period in the Tertiary era the climate was not yet differentiated into zones and there were then no hot and cold extremes as at present. The close of the Pliocene and the whole of the Pleistocene period was marked by violent changes of climate bringing on what is called the Glacial and Inter-Glacial epochs. But it is now conclusively established that before the advent of this period a luxuriant forest vegetation, which can only grow and exist at present in the tropical or temperate climate, flourished in the high latitude of Spitzbergen, where the sun goes below the horizon from November till March, thus showing that a warm climate prevailed in the Arctic regions in those days.

21 It was in the Quaternary or the Pleistocene period that the mild climate of these regions underwent sudden alterations producing what is called the Glacial period. The limits of this Glacial period may not so exactly coincide with those of the Pleistocene as to enable us to say that they were mathematically co-extensive, but, still, in a rough sense we may take these two periods as coinciding with each other. It is impossible within the limits of a short chapter to give even a summary of the evidence proving the existence of one or more Glacial epochs in the Pleistocene period. We may, however, briefly indicate its nature and see what the geologists and the physicists have to say as regards the causes that brought about such extensive changes of climate in the Quaternary era. The existence of the Glacial period is no longer a matter of doubt though scientific men are not agreed as to the causes which produced it. Ice-sheets have not totally disappeared from the surface of the earth and we can still watch the action of ice as glaciers in the valleys of the Alps or in the lands near the Pole, like Greenland which is still covered with a sheet of ice so thick as to make it unfit for the growth of plants or the habitation of animals. Studying the effects of glacial action in these places geologists have discovered abundant traces of similar action of ice in former times over the whole of Northern Europe and America. Rounded and scratched stones, till or boulder-clay, and the rounded appearance of rocks and mountains clearly point out that at one period in the history of our globe northern parts of Europe and America must have been covered for a long time with a sheet of ice several hundreds of feet in thickness. The ice which thus invaded the northern portion of America and Europe did not all radiate from the Pole. The evidence of the direction of the striæ, or scratches engraved on rocks by ice, undoubtedly proves that the ice-caps spread out from all elevated places or mountains in different directions. These ice-sheets of enormous thickness covered the whole of Scandinavia, filled up the North Sea; invaded Britain down to the Thames valley, greater portion of Germany and Russia as

22 far south as Moscow and almost as far east as the Urals. It is calculated that at least a million of square miles in Europe and more in North America were covered by the debris of rocks ground down by these glaciers and ice-caps, and it is from this debris that geologists now infer the existence of an Ice Age in early times. The examination of this debris shows that there are at least two series of boulder clay indicating two periods of glaciation. The debris of the second period has disturbed the first layer in many places, but enough remains to show that there were two distinct beds of boulder clay and drifts, belonging to two different periods. Prof. Geikie mentions four such Glacial periods, with corresponding Inter-Glacial periods, as having occurred in succession in Europe during the Pleistocene period. But though this opinion is not accepted by other geologists, yet the existence of two Glacial epochs, with an intervening Inter-Glacial period, is now considered as conclusively established. A succession of cold and warm climates must have characterized these Glacial and Inter-Glacial periods which were also accompanied by extensive movements of depression and elevation of land, the depression taking place after the land was weighed down with the enormous mass of ice. Thus a period of glaciation was marked by elevation, extreme cold and the invasion of the ice-caps over regions of the present Temperate zone; while an inter-glacial period was accompanied by depression of land and milder and congenial climate which made even the Arctic regions habitable. The remains of the Paleolithic man have been found often imbedded between the two boulder-clays of two different Glacial periods, a fact which conclusively establishes the existence of man in the Inter-Glacial period in the Quaternary era. Prof. Geikie speaking of the changes of climate in the Glacial and Inter-Glacial period remarks that “during the Inter-Glacial period the climate was characterized by clement winters and cool summers so that the tropical plants and animals, like elephants, rhinoceroses and hippopotamuses, ranged over the whole of the Arctic region, and in spite of

23 numerous fierce carnivora, the Paleolithic man had no unpleasant habitation there.”* It will thus be seen that in point of climate the Pleistocene period, or the early Quaternary era, was intermediate between the early geological ages when uniform genial climate prevailed over the globe, and the modern period when it is differentiated into zones. It was, so to speak, a transitional period marked by violent changes in the climate, that was mild and genial in the Inter-Glacial, and severe and inclement during the Glacial period. It was at the beginning of the Post-Glacial or the Recent period that modern climatic conditions were established. Prof. Geikie is, however, of opinion that even the beginning of the Post-Glacial period was marked, at least in North-Western Europe, by two alternations of genial and rainy-cold climate before the present climatic conditions became established.† But though the fact of the Ice Age and the existence of a milder climate within the Arctic regions in the Inter-Glacial time is indubitably proved yet scientific men have not been as yet able to trace satisfactorily the causes of this great catastrophe. Such immense mass of ice as covered the whole of Northern Europe and America during this period could not, like anything else, come out of nothing., There must be heat enough in certain parts of the globe to create by evaporation sufficient vapor and aerial currents are required to transfer it to the colder regions of the globe, there to be precipitated in the form of ice. Any theory regarding the cause of the Ice Age which fails to take this fact into account is not only inadequate but worthless. A succession of Glacial periods, or at any rate, the occurrence of two Glacial periods, must again be accounted for by the theory that may be proposed to explain these changes; and if we test the different theories advanced in this way, many of them will be at once found to be untenable. It was, for instance, once urged that the Gulf Stream, which, at present, imparts warmth to the countries in the North-West of Europe, might have been turned away from its course in * Fragments of Earth Lore, p. 266. † Prehistoric Europe, p. 530.

24 the Pleistocene period by the submergence of the Isthmus of Panama, thus converting the countries on the North-Western coast of Europe into lands covered by ice. There is, however, no geological evidence to show that the Isthmus of Panama was submerged in the Pleistocene period and we must, therefore, give up this hypothesis. Another theory started to account for the catastrophe was that the earth must have passed through cold and hot regions of space, thus giving rise to Glacial and Inter-Glacial periods respectively. But this too is unsupported by any evidence. A third suggestion advanced was that the supply of solar heat on earth must have varied in such a way as to give rise to warm and cold climates but this was shown to be a mere conjecture. A change in the position of the earth’s axis might indeed cause such sudden changes in the climate; but a change in the axis means a change in the equator and as the earth owing to its diurnal rotation causes the equatorial regions to bulge out, a change in the axis would give rise to a second equatorial protuberance, which, however, is not observable and that the theory cannot therefore, be accepted. A gradual cooling of the earth would make the Polar regions habitable before the other parts of the globe; but a succession of Glacial epochs cannot be accounted for on this theory. Thus out of the various theories advanced to account for the vicissitudes of climate in the Pleistocene period only two have now remained in the field, the first that of Lyell which explains the changes by assuming different distribution of land and water combined with sudden elevation and submergence of large landed areas and the second that of Croll which traces the glaciation to the precession of the equinoxes combined with the high value of the eccentricity of the earth’s orbit. Lyell’s theory has been worked out by Wallace who shows that such geographical changes are by themselves sufficient to produce heat and cold required to bring on the Glacial and Inter-Glacial periods. We have seen that in earlier geological ages a pleasant and equable climate prevailed over the whole surface of the globe owing mainly to different

25 distribution of land and water and the theory advanced by Lyell to account for the Glacial epoch is practically the same. Great elevation and depression of extensive areas can be effected only in thousands of years, and those who support Lyell’s theory are of opinion that the duration of the Glacial epoch must be taken to be about 200,000 years in order to account for all the geographical and geological changes, which according to them, were the principal causes of the Glacial period. But there are other geologists, of the same school, who hold that the Glacial period may not have lasted longer than about 20 to 25 thousand years. The difference between the two estimates is enormous; but in the present state of geological evidence it is difficult to decide in favor of any one of these views. All that we can safely say is that the duration of the Pleistocene period, which included at least two Glacial and one Inter-Glacial epoch, must have been very much longer than the period of time which has elapsed since the- commencement of the Post-Glacial period. According to Sir Robert Ball the whole difficulty of finding out the causes of the Glacial period vanishes when the solution of the problem is sought for in astronomy rather than in geography. Changes which seem to be so gigantic on the globe are, it is said, but daily wrought by cosmical forces with which we are familiar in astronomy, and one of the chief merits of Croll’s theory is supposed to consist in the fact that it satisfactorily accounts for a succession of Glacial and Inter-Glacial epochs during the Pleistocene period. Dr. Croll in his Climate and Time and Climate and Cosmology has tried to explain and establish his theory by elaborate calculations, showing that the changes in the values of the variable elements in the motion of the earth round the sun can adequately account for the climatic changes in the Pleistocene period. We shall first briefly state Dr. Croll’s theory and then give the opinions of experts as regards its probability. Let PQ'AQ represent the orbit of the earth round the sun. This orbit is an ellipse, and the sun, instead of being in the centre C, is in one of the focii S or s. Let the sun be at S.

26 Then the distance of the sun from the earth when the latter is at P would be the shortest, while, when the earth is at A it will be the longest. These points P and A are respectively called perihelion and aphelion. The seasons are caused, as stated above, by the axis of the earth being inclined to the plane of its orbit. Thus when the earth is at P and the axis turned away from the sun, it will produce winter in the northern hemisphere; while when the earth is at A, the axis, retaining its direction, will be now turned towards the sun, and there will be summer in the northern hemisphere. If the axis of the earth had no motion of its own, the seasons will always occur at the same points in the orbit of the earth, as, for instance, the winter in the northern hemisphere at P and the summer at A. But this axis describes a small circle round the pole of the ecliptic in a cycle of 25,868 years, giving rise to what is called the precession of the equinoxes, and consequently the indication of the earth’s axis to the plane of its orbit is not always the same at any given point in its orbit during this period. This causes the seasons to occur at different points in the earth’s orbit during this great cycle. Thus if the winter in the northern hemisphere occurred when the earth was at P at one time, some time after it will occur at and the succeeding points in the orbit until the end of the cycle, when it will again occur at P. The same will be the case in regard to summer at the point A and equinoxes at Q and Q'. In the diagram the dotted line qq' and pa represent the new positions which the line QQ' and PA will assume if they revolve in the way stated above. It must also be noted that though the winter in the northern hemisphere may occur when the earth is at p instead of at P, owing to the aforesaid motion of its axis, yet the orbit of the

27 earth and the points of perihelion and aphelion are relatively fixed and unchangeable. Therefore, if the winter is the northern hemisphere occurs at p, the earth’s distance from the sun at the point will be greater than when the earth was at P. Similarly, in the course of the cycle above mentioned, the winter in the northern hemisphere will once occur at A, and the distance of the earth from the sun will then be the longest. Now there is a vast difference between a winter occurring when the earth is at P and a winter occurring when it is at A. In the first case, the point P being nearest to the sun, the severity of the winter will be greatly, modified by the nearness of the sun. But at A the sun is farthest removed from the earth, and the winter, when the earth is at A, will be naturally very severe; and during the cycle the winter must once occur at A. The length of the cycle is 25,868 years, and ordinarily speaking half of this period must elapse before the occurrence of winter is transferred from the earth’s position at P to its position at A. But it is found that the points P and A have a small motion of their own in the direction opposite to that in which the line of equinoxes QQ' or the winter point p moves along the orbit. The above cycle of 25,868 years is, therefore, reduced to 20,984, or, in round number 21,000 years. Thus if the winter in one hemisphere occurs when the earth is at P, the point nearest to the sun in the orbit, it will occur in the same hemisphere at A after a lapse of 10,500 years. It may be here mentioned that in about 1250 A.D., the winter in the northern hemisphere occurred when the earth in its orbit was at P, and that in about 11,750 A.D. the earth will be again at A, that is, at its longest distance from the sun at the winter time, giving rise to a severe winter. Calculating backwards it may be seen that the last severe winter at A must have occurred in the year 9,250 B.C.* It need not be mentioned that the winter in one hemisphere corresponds with the summer in the other, and that what is said about winter in the northern. * See Herschel’s Outlines of Astronomy, Ed. 1883, Arts. 368, 369.

28 hemisphere applies mutatis mutandis to seasonal changes in the southern hemisphere. There is another consideration which we must take into account in estimating the severity of winter or the mildness of summer in any hemisphere. If the summer be defined to be the period of time required by the earth to travel from one equinoctial point Q' to another equinoctial point Q, this interval cannot always be constant for we have seen that the winter and summer points (P and A), and with them the equinoctial points (Q and Q') are not stationary, but revolve along the orbit once in 21,000 years. Had the orbit been a circle, the lines qq' and pa will have always divided it in equal parts. But the orbit being an ellipse these two sections are unequal. For instance, suppose that the winter occurs when the earth is at P, then the duration of the summer will be represented by Q'AQ, but when the winter occurs at A the summer time will be represented by QPQ', a segment of the ellipse necessarily smaller than Q'AQ. This inequality is due to the ellipticity of the orbit, and the more elongated or elliptic the orbit is the greater will be the difference between the durations of summer and winter in a hemisphere. Now the ellipticity of the orbit is measured by the difference between the mean and the greatest distance of the earth from the sun, and is called in astronomy the eccentricity of the earth’s orbit. This eccentricity of the earth’s orbit is not a constant quantity but varies, though slowly, in course of time, making the orbit more and more elliptical until it reaches a maximum value, when it again begins to reduce until the original value is reached. The duration of summer and winter in a hemisphere, therefore, varies as the value of the eccentricity of the earth’s orbit at that time; and it has been stated above that the difference between the duration of summer and winter also depends on the position of the equinoctial line or of the points in the earth’s orbit at which the winter and the summer in a hemisphere occur. As the joint result of these two variations, the difference between the durations of

29 summer and winter would be the longest, when the eccentricity of the earth is at its maximum and according as the winter and summer occur at the points of perihelion or aphelion. It has been found that this difference is equal to 33 days at the highest, and that at the present day it is about 7½ days. Thus if the winter in the northern hemisphere occurs when the earth is at P in its orbit and the eccentricity is at its maximum, the winter will be shorter by 33 days than the summer of the time. But this position will be altered after 10,500 years when the winter, occurring at A, will, in its turn, be longer than the corresponding summer by the same length of time, viz. 33 days. Now, since the earth describes equal areas in equal times in its orbit, Herschel supposed that in spite of the difference between the duration of summer and winter noticed above, the whole earth received equal amount of heat while passing from one equinox to another, the “inequality in the intensities of solar radiation in the two intervals being precisely compensated by the opposite inequality in the duration of the intervals themselves.” Accepting this statement Dr. Croll understated his ease to a certain extent. But Sir Robert Ball, formerly the Astronomer Royal of Ireland, in his recent work On the Cause of an Ice Age has demonstrated, by mathematical calculation, that the above supposition is erroneous, and that the total amount of heat received from the sun by each hemisphere in summer and winter varies as the obliquity of the earth or the inclination of its axis to the ecliptic, but is practically independent of the eccentricity of the earth’s orbit. Taking the total sun-heat received in a year by each hemisphere to be 365 units, or on an average one unit a day, and taking the obliquity to be 23° 27', Sir Robert Ball has calculated that each hemisphere would receive 229 of these heat-units during summer and only 136 during winter, whatever the eccentricity of the earth may be. But though these figures are not affected by the eccentricity of the orbit, yet we have seen that the duration of the summer or winter does vary as the eccentricity

30 Supposing, therefore, that we have the longest winter in the northern hemisphere, we shall have to distribute 229 heat-units over 166 days of a short summer, and 136 heat-units over 199 days of a long winter of the same period. In other words, the difference between the daily average heat in summer and winter will, in such a case, be the greatest, producing shorter but warmer summers and longer and colder winters, and ice and snow accumulated in the long winter will not be melted or removed by the heat of the sun in the short summer, giving rise, thereby, to what is known as the Glacial period in the northern hemisphere. From what has been stated above, it may be seen that the southern hemisphere during this period will have long and cool summers and short and warm winters, a condition precisely reverse to that in the northern hemisphere. In short the Glacial and Inter-Glacial periods in the two hemispheres will alternate with each other every 10,500 years, if the eccentricity of the earth be sufficiently great to make a perceptibly large difference between the winters and the summers in each hemisphere. If Dr. Croll had gone only so far, his position would have been unassailable, for the cause enumerated above, is sufficiently potent to produce the climatic changes attributed to it. At any rate, if this was not the sole cause of a succession of Glacial and Inter-Glacial periods, their could be no doubt that it must have been an important contributory cause in bringing about these changes. But taking the value of the eccentricity of the earth’s orbit from the tables of Leverrier, Dr. Croll calculated that during the last three million years there were three periods of maximum eccentricity, the first of 170,000, the second of 260,000, and the third of 160,000 years; and that 80,000 years have elapsed since the close of the third or the last period. According to Dr. Croll the Glacial epoch in the Pleistocene period must, therefore, have begun 240,000 years ago, and ended, followed by the Post-Glacial period, about 80,000 years ago. During this long period of 160,000 years, there must have been several

31 alternations of mild and severe climates, according as the winter in a hemisphere occurred when the earth was at perihelion or aphelion in its orbit, which happened every 10,500 years during the period. But as the cold epoch can be at its maximum only during the early part of each period, according to Dr. Croll’s theory, the last epoch of maximum glaciation must be placed 200,000 years ago, or about 40,000 years after the commencement of the last period of maximum eccentricity. The reliability of these elaborate calculations has, however, been questioned by astronomers and geologists alike. Sir Robert Ball, who supports Croll in every other respect, has himself refrained from making any astronomical calculations regarding the maximum value of the eccentricity of the earth’s orbit, or the time when the last Glacial epoch should have occurred, or when the next would take place. “I cannot say”, he observes, “when the last (Glacial epoch) took place, nor when the next may be expected. No one who is competent to deal with mathematical formulae would venture on such predictions in the present state of our knowledge.” Prof. Newcomb of New York, another astronomer of repute, in his review of Dr. Croll’s Climate and Time, has also pointed out how in the present state of astronomical knowledge it is impossible to place any reliance on the values of eccentricity computed for epoches, distant by millions of years, as the value of this eccentricity depends upon elements, many of which are uncertain, and this is especially the case when one has to deal with long geological eras. The only reply made by Dr. Croll to this criticism is that his figures were correctly worked up from the values of the eccentricity according to the latest correction of Mr. Stockwell.† This, however, is hardly a satisfactory reply, inasmuch as Prof. Newcomb’s objection refers not to the correctness of the mathematical work, but to * On the Cause of an Ice Age, p. 152. † Climate and Cosmology, p. 39.

32 the impossibility of correctly ascertaining the very data from which the values of the eccentricity were obtained. It was once supposed that the duration of each of Dr. Croll’s different periods admirably fitted in with the geological evidence, and fully corroborated the estimates of time supposed to be required for the extensive geographical changes which accompanied the Glacial and Inter-Glacial periods. But geologists have now begun to take a more sober view of this extravagant figures and calculations. According to Croll’s calculation there were three periods of maximum eccentricity during the last three million years, and there should, therefore, be three periods of glaciation corresponding to these, each including several Glacial and Inter-Glacial epochs. But there is no geological evidence of the existence of such Glacial epochs in early geological eras, except, perhaps, in the Permian and Carboniferous periods of the Paleozoic or the Primary age. An attempt is made to meet this objection by replying that though the eccentricity was greatest at one period in the early geological eras, yet, as the geographical distribution of land and water was then essentially different from what it was in the Quaternary era the high value of the eccentricity did not then produce the climatic changes it did in the Pleistocene period. This reply practically concedes that the high eccentricity of the earth’s orbit, combined with the occurrence of winter when the earth is at aphelion, is not by itself sufficient to bring about a Glacial period; and it may, therefore, be well urged that a Glacial epoch may occur even when the eccentricity is not at its maximum. Another point in which Dr. Croll’s theory conflicts with the geological evidence is the date of the close of the last Glacial epoch, as ascertained, by the American geologists, from estimates based on the erosion of valleys since the close of the last Glacial period. It is pointed out in the last chapter that these estimates do not carry the beginning of the Post-Glacial period much further than about 10,000 years ago at the best; while Dr. Croll’s calculation would carry it back to 80 or 100 thousand years. This is a

33 serious difference and even Prof. Geikie, who does not entirely accept the American view, is obliged to admit that though Dr. Croll’s theory is the only theory that accounts for the succession of Glacial epochs and therefore, the only correct theory, yet the formula employed by him to calculate the values of the eccentricity of the earth’s orbit may be incorrect and that we may thus account for the wide discrepancy between his inference and the conclusions based upon hard geological facts, which cannot be lightly set aside.* The judgment recently pronounced by Mr. Hudleston is still more severe. In his opening address, as President of the geological section of the meeting of the British Association in 1898, he is reported to have remarked, “There is probably nothing more extraordinary in the history of modern investigation than the extent to which geologists of an earlier date permitted themselves to be led away by the fascinating theories of Croll. The astronomical explanation of the “Will-o’-the-wisp,” the cause of the great Ice Age, is at present greatly discredited and we begin to estimate at their true value those elaborate calculations which were made to account for events, which, in all probability, never occurred. Extravagance begets extravagance and the unreasonable speculations of men like Belt and Croll have caused some of our recent students to suffer from the nightmare.”† This criticism appears to be rather severe; fox though Dr. Croll’s elaborate calculations may be extravagant, yet we must give him the credit for not merely suggesting but working out, the effect of a cosmical cause which under certain circumstances is powerful enough to produce extensive changes in the climate of the globe. But in spite of these remarks, it cannot be doubted that the duration of the Glacial period, comprising at least two Glacial and one Inter-Glacial epoch, must have been very much longer thin that of the Post-Glacial period. For, independently * Fragments of Earth Lore, p. 287. † See The Nature, Sept. 15, 1898.

34 of the eccentricity of the earth’s orbit, the occurrence of winter at aphelion is by itself sure to contribute to the production of the Ice Age, if other causes and circumstances, either those suggested by Lyell; or others, are favorable and 21,000 years must elapse between two successive occurrences of winter at aphelion. For two Glacial epochs with an intervening Inter-Glacial period, we must, therefore, allow a period longer than 21,000 years, even if the question of the eccentricity of the earth’s orbit be kept aside while, if, with Prof. Geikie, we suppose that there were five Glacial (four in the Pleistocene and one at the close of the Pliocene period) and four Inter-Glacial epochs the duration must be extended to something like 80,000 years. It is unnecessary to go further into these scientific and geological discussions. I have already stated before that my object is to trace from positive evidence contained in the Vedic literature the home of the Vedic and, therefore, also of the other Aryan races, long before they settled in Europe or on the banks of the Oxus, the Jaxartes, or the Indus; and so far as this purpose is concerned, the results of the latest scientific researches, discussed in this and the previous chapter, may now be summed up as follows: — (1) In the very beginning of the Neolithic age Europe is found to be inhabited by races,, from whom the present races of Europe speaking Aryan languages are descended. (2) But though the existence of an Aryan race in Europe in early Neolithic times is thus established, and, therefore, the theory of migrations from an Asiatic home in Post-Glacial times is untenable, it does not prove that the Aryan race was autochthonous in Europe, and the question of its original home cannot, therefore, be regarded as finally settled. (3) There are good reasons for supposing that the metal age was introduced into Europe by Foreign people. (4) The different ages of Stone, Bronze and Iron were not synchronous in different countries, and the high state of civilization in Egypt is not, therefore, inconsistent with the Neolithic stage of European civilization at the time.

35 (5) According to the latest geological evidence, which cannot be lightly set aside, the last Glacial period must have closed and the Post-Glacial commenced at about 10,000 years ago, or 8,000 B.C. at the best, and the freshness of the Siberian fossil-deposits favors this view. (6) Man is not merely Post-Glacial as he was believed to be some years ago, and there is conclusive geological evidence to prove his wide-spread existence in the Quaternary, if not also in Tertiary, era. (7) There were at least two Glacial and one Inter-Glacial period, and the geographical distribution of land and water on the earth during the Inter-Glacial period was quite different from what it is at present. (8) There were great vicissitudes of climate in the Pleistocene period, it being cold and inclement during the Glacial, and mild and temperate in the Inter-Glacial period, even as far as the Polar regions. (9) There is enough evidence to show that the Arctic regions, both in Asia and Europe, were characterized in the Inter-Glacial period by cool summers and warm winters — a sort of, what Herschel calls, a perpetual spring; and that places like Spitzbergen, where the sun goes below the horizon from November till March, were once the seat of luxuriant vegetation, that grows, at present, only in the temperate or the tropical climate. (10) It was the coming on of the Glacial age that destroyed this genial climate, and rendered the regions unsuited for the habitation of tropical plants and animals. (11) There are various estimates regarding the duration of the Glacial period, but in the present state of our knowledge it is safer to rely on geology than on astronomy in this respect, though as regards the causes of the Ice Age the astronomical explanation appears to be more probable. (12) According to Prof. Geikie there is evidence to hold that there were, in all, five Glacial and four Inter-Glacial epochs, and that even the beginning of the Post-Glacial

36 period was marked by two successions of cold and genial climate, at least in the North-West of Europe. (13) Several eminent scientific men have already advanced the theory that the cradle of the human race must be sought for in the Arctic regions and that the plant and animal life also originated in the same place. It will thus be seen that if the Vedic evidence points to an Arctic home, where the ancestors of the Vedic Ṛiṣhis lived in ancient times, there is at any rate nothing in the latest scientific discoveries which would warrant us in considering this result as a priori improbable. On the contrary there is much in these researches that suggests such a hypothesis, and as a matter of fact, several scientific men have now been led to think that we must look for the cradle of the human race in the Arctic regions.