TRANSACTIONS OF THE SECTIONS. 83 



Sir Charles Lyell gives the annual discharge of sediment by the Ganges and 

 Brahmapootra as forty thousand millions of cubic feet, which are equal to a circle 

 surrounding the earth's mean circumference two miles broad and one yard thick, 

 in 10-5 years and 50 days. This enormous denudation will in no long geological 

 period reduce the Himalayas down to the snow-line. All other mountains and 

 land in the world (except deserts) are also being denuded, year by year, by means of 

 rain and rivers, avalanches, glaciers, earthquakes, and alternate frost and thaw. 

 For example, the river Pinder, an affluent of the Ganges, has a fall of 500 feet 

 per mile tor 11 miles ; its water is all white foam, and has force enough to cany 

 along large boulders, which, as well as the river's bed, become broken, commi- 

 nuted, and abraded. For 16,000 feet in height of Mount Jawahir, there is a de- 

 tritus of loose rocks and stones, evidently fallen from the upper part of the moun- 

 tain. The like effects have been observed at the Matterhorn, in Tierra del Fuego, 

 the Chilian Andes, Australia, Spitzbergen, and some small English mountains. 

 In the Himalayas there are annual shocks of earthquakes, some of them severe, 

 which loosen and bring down rocks. Avalanches bring down masses of stone, 

 and glaciers convey along lines of stones called "moraines;" and alternate frost 

 and thaw split and comminute rocks and stones. In these ways mountains are 

 lowered, and in time there will be no mountain as high as the snow-line (unless 

 risings by subterranean action occur again), and then a warmer period will be the 

 consequence. And when the land is reduced to sea-level, the climate will be still 

 warmer; because the air is chiefly warmed by heat transmitted and radiated 

 from the earth, and land increases the cold by abstracting heat from the air in 

 high latitudes and where the land is high, and augments the heat by radiatioiji 

 in low latitudes and where the ground is low; and water absorbs and retains 

 solar heat *. 



The latest glacial epoch seems to have been in the Recent, post-Pliocene, 

 and Newer Pliocene periods. Older formations, as far back as the Pei-mian in- 

 clusive, were warmer than at present, excepting some floating ice in the Cretaceous 

 and Permian. A difficulty has been felt about the Miocene strata of the Superga 

 Hill (Turin), how they became mixed up with erratics. It is now suggested 

 that the hill and its strata, being of a conical form, must have been uplifted ; and 

 probably so in the Glacial period, whilst a glacier carrying the erratics rested upon 

 it. The like may be true of the " flysch " conglomerate of Eocene date in the 

 Alps. The largest part of Europe, the Sahara of Africa, and much of the basin of 

 the St. Lawrence have been submarine since the early Eocene period f. And 

 these submergences apparently assisted to bring on the Glacial period, because 

 the sea above the submerged land would absorb and retain much solar heat ; and 

 the uplifting of the mountains, now to be stated, must have added much to the 

 cold. _ Since the commencement of the Eocene period the Alps have acquired 4000 

 and, in some places, more than 10,000 feet of their present height ; and the Py- 

 renees have attained their present height, which in Mont Perdu is 11,000 feet %• The 

 Sierra Nevada, 11,000, and the Caucasus, 15,000 feet, had not then risen §. Prof. 

 E. Forbes stated that Sorata (Andes), 24,812 feet high, contains Tertiary fossils to 

 its summit. Mr. Darwin found chalk shells nearly 14,000 feet high in the Chi- 

 lian Andes, and Capt. Strachey found Oolitic fossils 18,400 feet high in the 

 Himalayas. All these mountains must have been upheaved since the Coal- 

 period, and consequently we have no proof that there were theii any mountains 

 at all with summits as high as the snow-line ; and they must have been higher 

 than now, and consequently colder, by just as much as they have been denuded. 

 But while lofty mountains have been eliminated as a source of cold in the Coal- 

 period, it can also be proved that there was then probably much more dry land in 

 the south to radiate heat, and produce a warm, equable, and humid climate which 

 the Coal period requires. The annual quantity of solar heat thrown upon the 

 earth during the geological period has probably been nearly uniform ; but not 

 so its effects on the earth's climate. Capt. Stiu-t'found the sandy deserts of Aus- 

 tralia so hot that they were almost a molten surface. On the other hand, if the 

 gite of Australia were now occupied even by comparatively shallow water, much 



* Sir John Herschel, ' Outlines of Astronomy,' p. 236. 

 t Sir C. Lyell's ' Principles of Geology.' | Ibid 



§ Ibid. Map, p. 251, 

 6* 



