418 ORIGIN OF SPECIES 



the equator, we know, from the excellent researches of Dr. 

 J. Haast and Dr. Hector, that in New Zealand immense 

 glaciers formerly descended to a low level; and the same 

 plants found by Dr. Hooker on widely separated mountains 

 in this island tell the same story of a former cold period. 

 From facts communicated to me by the Rev. W. B. Clarke, 

 it appears also that there are traces of former glacial action 

 on the mountains of the south-eastern corner of Australia. 



Looking to America; in the northern half, ice-borne frag- 

 ments of rock have been observed on the eastern side of the 

 continent, as far south as lat. 36° -37°, and on the shores of 

 the Pacific, where the climate is now so different, as far 

 south as lat. 46°. Erratic boulders have, also, been noticed 

 on the Rocky Mountains. In the Cordillera of South Amer- 

 ica, nearly under the equator, glaciers once extended far be- 

 low their present level. In Central Chile I examined a vast 

 mound of detritus with great boulders, crossing the Portillo 

 valley, which there can hardly be a doubt once formed a huge 

 moraine; and Mr. D. Forbes informs me that he found in 

 various parts of the Cordillera, from lat. 13° to 30° S., at 

 about the height of 12,000 feet, deeply-furrowed rocks, re- 

 sembling those with which he was familiar in Norway, and 

 likewise great masses of detritus, including grooved pebbles. 

 Along this whole space of the Cordillera true glaciers do not 

 now exist even at much more considerable heights. Farther 

 south on both sides of the continent, from lat. 41° to the 

 southernmost extremity, we have the clearest evidence of 

 former glacial action, in numerous immense boulders trans- 

 ported far from their parent source. 



From these several facts, namely from the glacial action 

 having extended all round the northern and southern hemi- 

 spheres — from the period having been in a geological sense 

 recent in both hemispheres — from its having lasted in both 

 during a great length of time, as may be inferred from the 

 amount of work effected — and lastly from glaciers having 

 recently descended to a low level along the whole line of the 

 Cordillera, it at one time appeared to me that we could not 

 avoid the conclusion that the temperature of the whole world 

 had been simultaneously lowered during the Glacial period. 

 But now Mr. CroU, in a series of admirable memoirs, has 



