222 PKOFESSOR JAMES GE1KIE, LL.D., D.C.L., F.R.S., ETC., ON 



unexplained a residuum of less conspicuous, but nevertheless 

 well-proved facts, then, however strongly it may be fortified, 

 it must assuredly fall. 



As already remarked, there are many phenomena in the 

 interpretation of which geologists are generally agreed. It 

 is, for example, no longer disputed that in Pleistocene times 

 vast sheets of ice — continental triers de glace — covered broad 

 areas in Europe and North America, and that extensive snow- 

 fields and large local glaciers existed in many mountain- 

 regions where snow-fields and glaciers are now unknown, or 

 only meagrely developed. As Professor Penck and others 

 have shown, the line of perennial snow during the glacial 

 period must have been depressed in Central Europe for 3,000 

 or 3,500 feet — a depression which would correspond approxi- 

 mately to a general lowering of the mean annual temperature 

 of about 10° or 11° F.* This, as Penck points out, would 

 bring the climate of Northern Norway down to Southern 

 Germany, and the climate of Sweden to Austria and Moravia, 

 while that of the Alps would be met with over the Mediter- 

 ranean. It is particularly worthy of notice that the lowering 

 of the temperature was not confined to North- Western and 

 Central Europe, but was general over the whole continent. 

 The Scoto-Scandinavian inland-ice covered many thousands 

 of square miles in the Northern and North- Western portion 

 of the continent ; in the Alps and other mountains of Middle 

 Europe great snow-fields and glaciers existed ; while further 

 south, as in the Sierra Nevada, Corsica, the Apennines, the 

 Despoto Dagh, etc., only a few isolated local glaciers appeared. 

 Still further south and south-east, as in North Africa and 

 Syria, rainy or pluvial conditions seem to have been contem- 

 poraneous with the glacial period of Europe. Thus, it is 

 highly probable — one might almost say certain — that precipi- 

 tation over the whole continent was greater than now. The 

 geographical distribution of glacial, fluvio-glacial, and other 

 Pleistocene deposits leads, in fine, to the conclusion that in 

 glacial times a wholesale displacement of climatic zones took 

 place. This is most clearly indicated by the Pleistocene 

 system of Europe and Asia, but it is hardly less marked in 

 the corresponding deposits of North America. 



It is further to be observed that the glacial conditions of 



* A ccording to Dr. Bruckner the general lowering of temperature may 

 not have exceeded 5j° to 7° F. Verhandl. d. 73 Jahresversam. d. Schwei- 

 zerfach, JVaturforschen, Oes. in Davos, 1890. 



