THE VOYAGE OF THE BEAGLE 261 



called tree-ferns ; and in these islands, and even as far south 

 as lat. 55 in the Macquarrie Islands, parrots abound. 



On the Height of the Snow-line, and on the Descent of 

 the Glaciers in South America. For the detailed authorities 

 for the following table, I must refer to the former edition : 



Latitude H c |ffiS? Ob ' 



Equatorial region ; mean result. 15,748 Humboldt. 



Bolivia, lat. 16 to 18 S 17,000 Pentland. 



Central Chile, lat. 33 S 14,500 to 15,000 Gillies, and the Author. 



Chiloe, lat. 41 to 43 S.... 6,000 Officers of the Beagle, 



and the Author. 



Tierra del Fuego, 54 S 3,50 to 4,000 King. 



As the height of the plane of perpetual snow seems chiefly to* 

 be determined by the extreme heat of the summer, rather than 

 by the mean temperature of the year, we ought not to be sur- 

 prised at its descent in the Strait of Magellan, where the sum- 

 mer is so cool, to only 3500 or 4000 feet above the level of the 

 sea ; although in Norway, we must travel to between lat. 67 

 and 70 N., that is, about 14 nearer the pole, to meet with 

 perpetual snow at this low level. The difference in height, 

 namely, about 9000 feet, between the snow-line on the Cor- 

 dillera behind Chiloe (with its highest points ranging from 

 only 5600 to 7500 feet) and in central Chile" (a distance of 

 only 9 of latitude), is truly wonderful. The land from the 

 southward of Chiloe to near Concepcion (lat. 37) is hidden 

 by one dense forest dripping with moisture. The sky is 

 cloudy, and we have seen how badly the fruits of southern 

 Europe succeed. In central Chile, on the other hand, a little 

 northward of Concepcion, the sky is generally clear, rain does 

 not fall for the seven summer months, and southern Euro- 

 pean fruits succeed admirably ; and even the sugar-cane has 

 been cultivated. 12 No doubt the plane of perpetual snow 

 undergoes the above remarkable flexure of 9000 feet, unpar- 



u On the Cordillera of central Chile, I believe the snow-line varies ex- 

 ceedingly in height in different summers. I was assured that during one 

 very dry and long summer, all the snow disappeared from Aconcagua, 

 although it attains the prodigious height of 23,000 feet. It is probable that 

 much of the snow at these great heights is evaporated rather than thawed. 



"Miers's Chile, vol. i. p. 4:5. It is said that the sugar-cane grew at 

 Ingenio, lat. 32 to 33, but not in sufficient quantity to make the manu- 

 facture profitable. In the valley of Quillota, south of Ingenio, I saw some 

 large date palm-trees. 



