1888.] 
137 
[Upham. 
noteworthy change in form or size. But the vicissitudes to which 
they were exposed during the last of our two principal glacial 
epochs, when the ice-sheet east of the Alleghenies advanced farther 
than in the earlier glaciation, were doubtless well adapted to cause 
both extinctions and modifications of species. How vast then must 
be the duration of time occupied in the evolution of the complex 
faunas and floras of our globe, and in the formation of all the fos- 
siliferous groups of rocks since the dawn of terrestrial life ! 
In various parts of Great Britain such transported Pleistocene 
shells are found in the till, both in its low and smooth tracts 1 and 
in its hilly and knolly terminal moraines traced by Professor Lewis, 
as well as in the associated kames. 2 Some of these fossiliferous 
glacial deposits occur in Ireland, northern Wales and northwestern 
England at heights 1,100 to 1,350 feet above the sea, and have 
been generally considered as proof of marine submergence to that 
depth. Instead of this, Lewis has shown 3 that the shells and frag- 
ments of shells found there were brought by the currents of the 
confluent ice-sheet which flowed southward from Scotland and 
northern Ireland, passing over the bottom of the Irish sea, there 
plowing up its marine deposits and shells, and carrying them up- 
ward as glacial drift to these elevations, so that they afford no 
testimony of the former subsidence of the land. This removes 
one of the most perplexing questions that glacialists have encoun- 
tered ; for nowhere else in the British Isles is there proof of any 
such submergence during or since the glacial period, the maximum 
known being 510 feet near Airdrie in Lanarkshire, Scotland. 4 At 
the same time the submergence on the southern coast of England 
was only from ten to sixty feet, 5 while no traces of raised beaches 
or of Pleistocene marine formations above the present sea level are 
found in the Shetland and Orkney islands. 6 
The occurrence of transported marine fossils in the till near 
Boston shows that during the epoch preceding the latest glacia- 
1 Geikie’s Great Ice Age, second ed., pp. 164-185, and 337-340. 
2 Quart. Journ. Geol. Soc., vol. xxx, 1874, pp. 27-42; xxxiv, 1878, pp. 383-397; 
xxxvi, 1880, pp. 351-355; xxxvii, 1881, pp. 351-369; and xliii, 1887, pp. 73-120; also, 
Geological Magazine, II, vol. i, 1874, pp. 193-197. 
a Report of the British Association for Adv. of Sci., Birmingham, 1886, pp. 632- 
635; Am. Naturalist, vol. xx, pp. 919-925, Nov., 1886; Am. Journ. Sci., ill, vol. xxxii, 
pp. 433-438, Dec., 1886. Also, see American Geologist, vol. ii, pp. 371-379, Dec., 1888. 
4 Quart. Journ. Geol. Soc., vol. vi, 1850, pp. 386-388; xxi, 1865, pp. 219-221. 
5 Quart. Journ. Geol. Soc., xxxiv, 1878, pp. 454-457; xxxix, 1883, p. 54. Geol. Mag., II, 
vol. ii, 1875, p.229; II, vi, 1879, pp. 166-172. 
6 Quart. Journ. Geol. Soc., xxxv, 1879, p. 810; xxxvi, 1880, p. 663. 
