ITS FIRST STAGE. 



of the glacial epoch, the land, as we shall shortly see, seems 

 to have been gradually subsiding, and this subsidence went 

 on to the extent of 1800 or 2000 feet below the existing 

 sea-level, converting a large portion of what is now Europe 

 and America into series of frozen straits and ice-clad islands. 

 When the land seems to have been at its greatest depres- 

 sion the cold appears to have attained its greatest intensity, 

 and at this stage we have the zenith and turning-point of 

 the glacial period. After the lapse, perhaps, of ages, a re- 

 verse action sets in ; the land begins to be re-elevated ; a 

 new cycle of temperature commences ; and the cold, though 

 still clinging in snow and glacier to the higher hills, is less 

 felt along the lower grounds and neighbouring sea-shores. 

 By-and-by, as the elevation continues, the glaciers melt 

 away from the hill-sides ; the icebergs and ice-packs dis- 

 appear from the seas ; the general climate improves ; plants 

 and land animals in newer species gradually take posses- 

 sion of the land ; and the existing order of things is imper- 

 ceptibly established. Such seem to have been the setting-in, 

 the creeping-on, the culmination, and the departure of the 

 glacial epoch. Let us now glance at the proofs by which 

 this advent, this subsidence, and this re-elevation can be 

 logically established. 



That the ice-epoch, like other great events in nature, 

 came on slowly and gradually, is abundantly evidenced by 

 the temperate or even coldly-temperate aspects of the flora 

 and fauna of the later, as compared with those of the middle 

 and earlier tertiaries. The eocene palms, crocodiles, turtles, 

 and monkeys do not appear in miocene strata ; the miocene 

 sycamores, chestnuts, and maples are replaced by pliocene 

 pines, beeches, and birches ; and thus over the tertiary areas 

 of Europe at least the declension of climate had been going 

 on for ages before the advent of the glacial period. How 

 far this declension was simultaneous over Asia and America 



