163 THE ORIGIN OF SPECIES 



the shores of the Pacific, where the climate is now so 

 different, as far south as latitude 46°. Erratic bowlders 

 have, also, been noticed on the Rocky Mountains. In 

 the Cordillera of South America, nearly under the equa- 

 tor, glaciers once extended far below their present level. 

 In Central Chile I examined a vast mound of detritus 

 with great bowlders, crossing the Portillo Valley, which 

 there can hardly be a doubt once formed a huge mo- 

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

 various parts of the Cordillera, from latitude 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 Cordil- 

 lera true glaciers do not now exist even at much more 

 considerable heights. Further south on both sides of the 

 continent, from latitude 41° to the southernmost extrem- 

 ity, we have the clearest evidence of former glacial ac- 

 tion, in numerous immense bowlders transported far from 

 their parent source. 



From these several facts, namely, from the glacial 

 action having extended all round the northern and south- 

 ern hemispheres — from the period having been in a geo- 

 logical 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 simul- 

 taneously lowered during the Glacial period. But now 

 Mr. CroU, in a series of admirable memoirs, has at- 



