Chap. XII.] ALTERNATE GLACIAL PERIODS. 335 



Alternate Glacial Periods in the North and South. 



But we must return to our more immediate subject. 1 am con- 

 vinced that Forbes's view may be largely extended. In Europe we 

 meet with the plainest evidence of tbe Glacial period, from tbe 

 western shores of Britain to the Oural range, and southward to the 

 Pyrenees. We may infer from the frozen mammals and nature 

 of the mountain vegetation, that Siberia was similarly affected. In 

 the Lebanon, according to Dr. Hooker, perpetual snow formerly 

 covered the central axis, and fed glaciers which rolled 4000 feet 

 down the valleys. The same observer has recently found great 

 moraines at a low level on the Atlas range in N. Africa. Along 

 the Himalaya, at points 900 miles apart, glaciers have left the 

 marks of their former low descent ; and in Sikkim, Dr. Hooker 

 saw maize growing on ancient and gigantic moraines. Southward 

 of the Asiatic continent, on the opposite side of 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 fragments 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 Pocky Mountains. In the Cor- 

 dillera of South America, nearly under the equator, glaciers once 

 extended far below their present level. In Central Chile I ex- 

 amined 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, resembling 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 con- 

 siderable 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 

 transported far from their parent source. 



From these several facts, namely from the glacial action having 



