246 GLACIERS AND THE SNOW-LINE. [chap. xt. 



Dr. Dieffenbach,* have trunks so thick and high that they 

 may be almost 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 : 



As the height of the plain 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 surprised at its descent in the Strait of Magellan, 

 where the summer 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 Cordillera behind Chiloe (with 

 its highest points ranging from only 5600 to 7500 feet) and 

 in central Chile t (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 



* See the German Translation of this Journal ; and for the other facts 

 Mr. Brown's appendix to Flinders's "Voyage." 



t On the Cordillera of central Chile, I believe the snow-line varies exceedingly 

 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 probabe that much of the snow at these 

 great height* »«« *vaporited, rather than thawed. 



