178 



NATURE 



[June 19, 1890 



temperature requisite for which is estimated at about 

 8° C. (46° F.). 



Much richer is the fossil flora of Spitzbergen, between 

 'j'j^ and 78§° N. lat. Here also conifers are dominant ; 

 among foliage trees are present several poplars, also 

 willows, alders, beeches, birches, large-leaved oaks, elms, 

 plane trees, walnuts, magnolias, maples, and others ; 

 accordingly the climate of Spitzbergen at that time 

 must have been much the same as the present climate of 

 Northern Germany. A still warmer climate is indicated 

 by the fossil flora of Greenland, which may be compared 

 with the present flora of the shores of the Lake of 

 Geneva. 



These are by no means the only instances of a similar 

 kind ; analogous discoveries have been made at many 

 different points in high northern latitudes ; for instance 

 in Siberia on the lower Lena, on the New Siberian Islands, 

 in Kamtschatka, Alaska, Sitka, Banks Land, and some 

 other points. It is not yet certainly determined to what 

 part of the Tertiary period these fossil remains belong. 

 While some regard them as Miocene or Upper Oligocene, 

 others consider them to be Eocene ; and good reasons 

 may be assigned for both these opinions. Whatever 

 may be the final decision is for our present purpose a 

 matter of minor importance. The point we have to 

 insist on is that in the polar regions, the mean 

 temperature of which is now below the freezing-point, 

 and in which only some of the lowest plants exist, there 

 was in Tertiary times a rich forest growth. The difference 

 between those times and the present was so great that for 

 Grinnell Land we cannot estimate it as less than 27° C. 

 (49° F.). 



Such a change is absolutely inconceivable so long as 

 we continue to regard as unalterable the present position 

 of the places in question with reference to the pole. We 

 cannot imagine any change in the distribution of land 

 and water, in marine currents, or in any other influential 

 factor, which, at a time comparatively so little distant 

 from the present, could have brought about a luxuriant 

 forest growth in Grinnell Land. This has long been 

 recognized, and in many quarters it has been contended 

 that the only explanation possible is a displacement of 

 the earth's axis of rotation. To this the answer has been 

 that the stations that have yielded the Tertiary plant- 

 remains form a circuit around the pole, a chain from 

 which, as an English geologist has expressed it, the pole 

 can no more escape than a rat from a trap in a ring of 

 terriers. 



In point of fact there is no need for assuming so 

 considerable a displacement of the pole since the 

 beginning of Tertiary times. There is, however, ample 

 room within the circle of the northern Tertiary plant 

 stations for such a change, and there are valid grounds for 

 such an assumption. For nowhere do the Tertiary plants 

 reach so far north, and yet nevertheless testify so 

 strongly to the existence of a warm climate as in the 

 quadrant in which lie Grinnell Land, Greenland, and 

 Spitzbergen ; when we pass over to the opposite quadrant 

 we find precisely the opposite case, for the Tertiary plants 

 of Alaska, in North-Western America have, in north 

 latitude 60°, scarcely more the character of a southern flora 

 than those of Spitzbergen in lat. 78°. 



From these considerations, it seems not improbable 

 that, at the time when these Tertiary plants lived, the 

 pole really had not the same position as now, but was 

 displaced from 10° to 20° in the direction of North-Eastern 

 Asia. The circumstances of the Tertiary deposits in 

 other places outside the polar regions agree very well with 

 this view. In Europe, as we have seen, a very warm 

 climate prevailed universally, but when we turn to other 

 countries we meet with a different result. The flora of 

 the Tertiary formations of the United States give no 

 indication of any essential increase of temperature, and 

 the fossil plants of the probably Miocene and Pliocene 



NO. 1077, ^'OL. 42] 



formations of Japan, according to the admirable investiga- 

 tions of Nathorst, point to a colder climate than that 

 which now prevails. These facts are obviously eminently 

 favourable to the idea of a displacement of the pole. 

 Curiously enough, we find in the yet but little known 

 Tertiary deposits of the southern hemisphere a somewhat 

 striking confirmation of this view, inasmuch as the marine 

 Tertiary Mollusca which occur in several parts of the 

 Chili coast, do not contain a single species indicative of 

 a warmer climate than that of the present day. 



Thus, then, it seems very probable that the position of 

 the pole in Tertiary times was different from that of 

 to-day, and only became as at present at the close of that 

 era. But on this assumption the extreme contrasts are 

 only somewhat palliated, the greater divergences some- 

 what reduced : no complete explanation is aff"orded of the 

 phenomena. Whatever position we may assign to the 

 pole, those places in which Tertiary forest trees are found 

 were in any case far nearer to it than is the present 

 northern limit of tree-growth ; and when we compare the 

 fossil floras of Europe and Japan, we find that the first 

 shows a much greater departure from the present state of 

 things in the direction of a warmer climate than does the 

 latter in the opposite direction. Thus we are led to the 

 conclusion that the climate of Tertiary times in general 

 was somewhat warmer than that of our own day, but by 

 no means to such an extent as that of the lands specially 

 favoured through the displacement of the pole, viz. 

 Grinnell Land, Greenland, Spitzbergen, and Western and 

 Central Europe. 



When from the Tertiary age we take another step 

 forward in time, and reach the Pleistocene, the immediate 

 forerunner of our present age, we meet with quite another 

 picture. The remarkable characteristics of this period 

 have been set forth by a skilled hand in this place, and I 

 need only refer to them in a few words and in so far as 

 is specially important in connection with our present 

 subject. 



At the setting in of the Pleistocene, the climate seems 

 to have been somewhat warmer than at present : figs, 

 laurels, and vines grew wild in Central Europe, and 

 among animals, we meet with certain fresh-water Mol- 

 lusca {Cyrena JIutnmalis) which afford a similar indication. 

 Then followed through the greater part of the Pleistocene 

 that extension of enormous ice masses, which, issuing from 

 Scandinavia, Finland, and the Russian Baltic provinces, 

 covered a great part of Europe and advanced to England, 

 Holland, the base of the mountains of Central Germany, 

 the Carpathians, and in Russia as far as Kiew, Woronesch, 

 and Nishni Novgorod. England, Scotland, and Ireland 

 were almost completely glaciated, the ice-sheet covered 

 nearly the whole Alpine region, a broad ice-girdle lay in 

 front of its northern base, and even the small hill-ranges 

 of Central Europe and some of the greater ranges of 

 Southern Europe developed independent glaciers. On a 

 still greater scale, similar phenomena present themselves 

 to us in North America, and in Northern Asia the greater 

 mountains were then glaciated. Also further south, in 

 the Himalaya and the Karakorum were enormous 

 glaciers, and the same in the neighbourhood of the 

 equator in the Sierra di Santa Martha in the northern 

 part of South America. In the southern hemisphere, 

 traces of glaciers occur very extensively in the southern 

 part of the same continent, and according to many 

 accounts also in South Africa. 



It was long doubtful whether the glaciation of the 

 northern and southern hemisphere took place simulta- 

 neously ; but there is now no longer any doubt that such 

 was really the case. Attempts have been made to explain 

 the formation of great ice-accumulations without any 

 depression of temperature, nay even in warm climates, 

 solely as the result of an excessive precipitation of rain 

 and snow, and in consequence of the prevalence of warm 

 winters and cool summers ; but these views are wholly 



