46(> MP. F. W. HAEMER OX THE [Aug. 190!^ 



have given the land-tracts an elevation greater than that of the 

 present day, of which we have no evidence. 



In the earth -movements of the Glacial Period, we may possihly 

 have a causa vera, or possibly one of the causae, which (admitting 

 the view here taken to be correct) induced the shifting of climatic 

 zones. Epeirogenic elianges, whether of upheaval or depression, 

 must have altered the distribution of pressure, and the consequent 

 direction of the prevalent winds, thus varying or limiting the areas 

 within whi^h the great ice-sheets could have existed. 



It has been sometimes assumed that movements, either of up- 

 heaval or subsidence, would have similarly affected different parts 

 of the iSTorthern Hemisphere at the same time : that, for example, 

 elevation and extension of the land occurred simultaneously in 

 jN^orth America and in Central America on the one hand, and in 

 Greenland, Scandinavia, and the British Isles on the other.^ It 

 seems at least possible, however, that the rising of one area may 

 have coincided with the sinking of another, and such earth-move- 

 ments were probabl}' of an irregular or complicated nature. Changes 

 of level in adjoining regions, during past epochs, have not always 

 been of an uniform character." The researches of American 

 geologists, especially, show that unequal movements of the earth's 

 crust were characteristic, in* the Western Continent, of the Glacial 

 Period. 



The case mentioned in one of my former papers, where the 

 elevation of the southern portion of the Anglo-Belgian Basin, in 

 Pliocene and Pleistocene times, coincided with a great subsidence 

 to the north, may also be mentioned.^ Moreover, the iee seems to 

 have moved, as to its general course, both in Europe and America, 

 in different directions at different periods, and this may not 

 improbably have been due to differential earth-movements.^ 



Such an elevation of the jNorth American continent as that 

 postulated by Le Conte would have lowered its temperature, and 

 so have favoured the accumulation of ice upon it ; but alterations 

 of level in outside areas might also have affected the climate of the 

 regions in which glaciation took place. 



Accepting, for the purpose of argument, Prof. J. W. Spencer's 

 view as to the Pleistocene elevation of the Antillean region, a 



^ See, for example, Hull, Journ. Yict. Inst. toI. xxx (1898) p. 805. 



^ Prof. James Geikie says that, at one stage of the Glacial Period, a depres- 

 sion which reached only 130 feet in Scotland attained 880 feet in Scandinavia. 

 Deposits containing northern shells are found at levels in North America 

 siiccessively higher as we trace ihem northward,, namely at 200 feet in New- 

 England, 560 feet at Montreal 1000 to 1500 feet in Labrador, and 1000 to 

 2000 feet in the Arctic Eegions; see 'Great Ice Age' 3rd ed. (1894) 

 pp. 780-81. 



3 Quart. Journ. Geol. Soc. vol. lii (1896) p. 748. 



* It may perhaps be worthy of notice that, both in Scandinavia and North 

 America, basin-shaped depressions now exist near regions where, during the. 

 Glacial Period, the ice lay thickest. Local changes in the uiovemeut of the 

 ice may, however, have been sometimes due to other causes. 



