April 12, 1894] 



NA TURE 



553 



continent, so long as the organisms affected by these 

 occurrences are less specialised mammals than ourselves ; 

 but we find it hard to believe in great physical or climatic 

 changes within the limits of our own written or unwritten 

 history. Moreover, our knowledge of the post-Pliocene 

 period is burdened with an excess of detail ; and broad 

 and sweeping generalisations seem at present out of the 

 question. And, if we go one step further, we may fairly 

 attribute our friendly agreement with regard to the con- 

 ditions of the older periods to our ignorance rather than 

 to our information. 



Sir William Dawson, in the present work, summarises 

 several previous pipers of his own, just as M. Gaudry's 

 detailed memoirs were summarised for general use in 

 " Les Ancetres de nos Animaux." This handy paper- 

 bound volume deals strictly with Canada, and is in no 

 way a " Theory of the Earth." It is moderate in tone, and 

 forms a serious plea for a rational treatment of the glacial 

 epoch. Whatever caused the cold conditions in the 

 northern hemisphere, or in parts of the northern hemi- 

 sphere, it is pointed out that the land-ice in Canada 

 radiated from two local centres, and not from the hypo- 

 thetical ice-cap at the pole. Readers of Nature will 

 remember the evidence brought forward by Dr. G. M. 

 Dawson as to the '' Laurentide" centre of glaciation on 

 the east and the " Cordilleran " centre on the west 

 (Nature, vol. xUi. p. 650). The conditions maintained 

 by Sir W. Dawson as most favourable to the develop- 

 ment of glaciers are high masses of land in proximity to 

 cold seas ; and, as he properly points out, these con- 

 ditions still prevail in North America to a greater extent 

 than in North Europe. They prevail, moreover, in Green- 

 land, but not in Grinnell Land, to cite two closely neigh- 

 bouring areas. 



It will be clear, then, that Sir W. Dawson urges that 

 differential earth-movement was the main factor in the 

 production of Canadian glaciation. The evidence of 

 marine shells in the drift, of the bones of whales, of the 

 character of the deposits themselves, all points to the 

 existence of wide areas of submergence. With regard, 

 for example, to the Cordilleran centre in British Columbia, 

 our author writes : — 



" The conditions were combined of a high mountain 

 chain with the Pacific on the west, and the then sub- 

 merged area of the great plains on the east, affording 

 next to Greenland the grandest gathering-ground for 

 snow and ice that the northern hemisphere has seen." 



Of recent years it has been far too generally assumed 

 that we have to picture the glaciers of the ice-age moving 

 across the features of the country as we at present know 

 them. The views of Prof. Suess with regard to earth- 

 movements in the historic period are perhaps only fair 

 criticism of somewhat hasty observations ; but, in face of 

 the extraordinary evidence of post- Pliocene upheavals, it 

 is at least irrational to believe that these terminated with 

 man's appearance on the globe. Many English "gla- 

 cialists " accept a recent submergence of their country to a 

 depth of 500 feet, and yet postulate the most catastrophic 

 occurrences to account for marine beds at twice that 

 height above the sea. Yet we now have, in addition to 

 the old Lyellian instances, such as the Astian or even 

 later beds in Sicily, which are elevated some 3000 feet, 

 NO. 1276, VOL. 49] 



evidence given us by Prof. Andrew Lawson of a post- 

 Pliocene uplift of the continental coast of California to 

 heights of from 800 to 1500 feet ; and Sir W. Dawson's 

 requirements to explain the distribution of the Canadian 

 drift are such as will seem moderate and natural to every 

 rational uniformitarian. 



On p. Ill of the present work, the author discusses the 

 possibility of distinguishing striations produced by the 

 "huge ice-islands" in shallow seas from the deeper and 

 firmer markings of true glacier-ice. Granted the sub- 

 mergence, which in itself assists in the formation of snow 

 and ice, the phenomena of the distribution of boulders 

 receive at once their simplest explanation ; and in chapter 

 V. the local details of the drifts are taken, area by 

 area, into consideration. Our own British islands must 

 similarly be discussed area by area. Because it seems 

 probable that Scotland in the glacial epoch was a local 

 Greenland, there is no reason why England should also 

 have been lifted above the sea. The evidence accumu- 

 lating in Ireland goes far in favour of a long submergence 

 of that country, with the production of an archipelago of 

 pictutesque and snow-capped islands. Hence it is that 

 we may welcome Sir W. Dawson's summary of results in 

 Canada as a reminder that land-ice and enormous ter- 

 minal moraines are not to be left in undisputed possession 

 of ihe field. We can even sympathise with him in his 

 final sense of irritation, when he charges some glacialists 

 with "misunderstanding or misrepresenting the glacial 

 work now going on in the arctic and boreal regions." 

 " These are grave accusations," he continues, " but I find 

 none of the memoirs or other writings of the current 

 school of glacialists free from such errors; and I think 

 it is time that reasonable men should discountenance 

 these misrepresentations, and adopt more moderate and 

 rational views." 



Of course Sir W. Dawson cannot resist the temptation 

 of stating as "an inevitable conclusion " (p. 289) "that 

 the origin of specific types is quite distinct from varietal 

 modification"; but this is a cheerful side-thrust, as it 

 were, in a work on quite another subject. On p. 36 the 

 use of " Neozoic " as equivalent to " Tertiary " seems un- 

 usual ; and on p. 51 there is a sentence on the origin of 

 fiords, quoted from an earlier paper by the author, which 

 describes them as " often evidences of the action of the 

 waves."' They may have nothing to do with glacial ex- 

 cavation, but still less can they be regarded as products 

 of marine erosion, unless the author confines himself to 

 the cases that he has specially examined in Nova Scotia. 



G. A. J. C. 



OUR BOOK SHELF. 



Gtitndziige ehier E7i{uickelungSi^eschichte der Pflanzen- 

 iL'e/t Mitttletiropas scit devi Ausgaiig dir lerticirzeit. 

 Von Dr. August Schulz. (Jena: Gustav Fischer, 1894. 

 Svo. pp. 206.) (Outlines of a History of the Develop- 

 ment of the Flora of Central Europe since the close of 

 the Tertiary Period.) 

 In a preliminary note by the author, we are in- 

 formed that this dissertation is an extract from a more 

 extended essay on the vegetation of Central Europe, 

 which present circumstances prevent him from publish- 

 ing in full. The title cited above is really that of the 

 first chapter of the work only. A secoijd deals with the 



