216 



KNOWLEDGE. 



[November 1, 1892. 



remarkable that this first definite appearance of the higher 

 forms of mammalian life should, so far as we know, have 

 been contemporaneous with the disappearance of so man}- 

 gigantic types of extinct reptiles, such as the dinosaurs, 

 the fish-lizards, and the plesiosaurs, which seem to have 

 reached the end of their term of existence at or about the 

 close of the secondary period. 



Most of these early tertiary mammals had molar teeth 

 carrying three cusps arranged in a triangle, like their 

 marsupial forerimners of the secondary, from which, 

 indeed, they were probably derived ; and at this com- 

 paratively early epoch the orders of mammals were but 

 very imperfectly differentiated from one another, it being 

 frequently difficult to decide which were carnivores and 

 which were ungulates. A few stages later differentiation 

 of ordinal types, accompanied by a great increase in the 

 bodily size of their representatives, had, however, taken 

 place ; and by the close of the eocene period, as exemplified 

 by the higher deposits of the Paris basin, most of the 

 present orders of mammals were well defined. Thence, 

 through the succeeding miocene and pliocsne epochs, there 

 went on a continual evolution of mammalian life, resulting 

 in the production of giant forms like the elephant and the 

 rhinoceros, and also characterized by the development of 

 specially modified types like the horse and the ox, which 

 differ so widely fi'om their five-toed ancestors. During the 

 same epochs antlers were developed in the deer and horns 

 in the rhinoceroses and oxen, while pigs and hippopotami 

 gradually acquired the enormous tusks with which their 

 existing representatives are armed. 



Seeing, then, that it was not till the advent of the 

 tertiary period that mammals assumed the position of the 

 dominant forms of life, Cuvier's memorable discovery in 

 the second decade of this century that the class dated from 

 the middle of the secondary period has in no essential 

 respect served to dispossess the first-named epoch from its 

 claim to the title of the Age of Mammals. 



THE NEW GEOLOGY. 



By the Rev. H. N. Hutchinson, B.A., F.G.S., Author of 

 " The Story of thf Hills,'' dr. 



A GOOD deal has lately been said about " the new 

 geology " ; perhaps a few words on this subject may 

 not be uninteresting to readers of Knowledge. It 

 has lately been dealt with at some length by Prof. 

 Lapworth in his address to the Geological Section 

 of the British Association, and by Prof. James Geikie in 

 his address to the Geographical Section. The publication 

 of Prof. Suess' work. Dux Antlit: der Erd (the Crust of the 

 Earth) a few years ago, has marked an important era in 

 geology, and a host of new and fascinating problems are 

 suggested by that remarkable book. 



Briefly, the new geology seeks to explain the cimous 

 distribution of land and water on the globe, thus connect- 

 ing together geology and geography as kindred sciences. 

 Nor does it deal only with the present state of things ; for 

 it treats of those up and down movements of the earth's 

 crust, whereby mountain ranges are ridged up thousands 

 of feet above the level of the sea wherein they were formed, 

 and the world's geographical features fi'om time to time 

 modified. Thus, it aims at restoring the ancient geography 

 of former periods in the world's history, and revealing the 

 evolution of continents. But this is not all, for, with 

 great boldness, some of the new leaders question certain 

 theories which, till recently, were considered to bb fairly 

 established, and have suggested new ideas which may lead 

 to important residts. Perhaps our former teachers had 



got more or less into a groove ; and there can be no harm 

 in trying to get out of it, so long as we do not wander 

 hopelessly from the track. 



it is true that some of the problems mentioned above 

 have, from time to time, attracted the attention of geolo- 

 gists ; but of late years, owing to desp sea explorations, 

 and the elaborate study of several mountain regions, so 

 much material has been collected that they begin to feel 

 the ground, on which once they lightly trod, somewhat 

 more secure. Between the years 1833 and 1852 a dis- 

 tinguished French geologist, M. Elie de Beaumont, put 

 forward a theory of mountain chains which attracted a 

 great deal of attention, and was accepted by many on 

 account of his mathematical knowledge as well as his 

 skill as a writer. Like the illustrious naturalist, Cuvier, 

 he believed in periods of violence or " revolutions," with 

 long intervals of repose between them. During the 

 latter strata were continually deposited, but during the 

 former mountain chains were supposed to have been 

 formsd by sudden and violent itpheaval. It is needless 

 to say that Lyell successfully dissipated this notion. 

 Elie de Beaumont endeavoured, with great skill and 

 learning, to show that all the mountain chains thrown up 

 during the same revolution had one uniform direction, 

 being parallel to each other within a few degrees of the 

 compass, even when situated in remote regions, whilst the 

 chains thrown up at difl'erent periods took different 

 directions. But although this bold theory broke down, 

 it set people thinking, and therefore served to pave the 

 way for those who came after. Now, mountains are, as it 

 were, the backbones of continents, and have evidently a 

 close relation to them, determining their general directions 

 and other features ; hence, problems connected with geo- 

 graphy, either of the present or of the past, must deal 

 with these important features. It seems to be 

 generaUy accepted that mountain ranges are wrinkles, or 

 complicated compressed folds in the earth's crust, while 

 the broad expanses of continents are low arches, 

 also made up of strata, and the ocean basins are 

 supposed to be broad troughs or inverted arches. 

 But this seems to imply that, even in the deepest depres- 

 sions of the ocean, strata exist similar to those of which 

 continental arches are composed, a conclusion which the 

 present writer cannot accept. We do not mean that they 

 would necessarily be of similar composition, but that the 

 theory implies a general similarity of structure and arrange- 

 ment, so that forces afl'ecting the continental strata in 

 such a way as to throw them into an upwanl curve, at the 

 same time threw those now under the ocean into a 

 (loiniiiard curve. The weak point in this theory, so 

 clearly expounded by Prof. Lapworth, is that we do not 

 know of the existence of anything like groups or series of 

 stratified rocks on the deeper parts of the sea bed, such as 

 we find forming the dry laud of continents. According to 

 his teaching, mountain chains, continental arches, and 

 even the deepest oceanic troughs, are simply diti'erent parts 

 of great groups of strata, some pushed upwards, some 

 downwards, and some squeezed up into highly-compressed 

 ridges to form mountain chains. Now, the continental 

 arches and the mountain ranges are made up of the same 

 materials, and are brought into position by the same 

 forces ; and at first sight one would conclude that the 

 oceanic depressions must be only another phase of the 

 same phenomena. But what if these hollows are primitive 

 depressions on the earth's surface uncovered by strata, 

 save for a thin layer of the " red clay," an abysmal deposit 

 discovered of late years by soundings ■? In that case the 

 contmuity is broken, and the oceanic trough is no longer 

 a continuation of the continental arch. This brings 



