1834.] HEIGHT OF SNOW-LINK. 233 



pared with the laud, seems to extend over the greater part of the 

 southern hemisphere ; and, as a consequence, the vegetation partakes 

 of a semi-tropical character. Tree-ferns thrive luxuriantly in Van 

 Diemen's Land (lat. 45), and I measured one trunk no less than 

 six feet in circumference. An arborescent fern was found by 

 Forster in New Zealand in 46, where orchideous plants are para- 

 sitical on the trees. In the Auckland Islands, ferns, according to 

 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 : 



^u<le. SKAS* 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. . . 3,500 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 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 Chile, on the other hand, a little northward of Con- 

 cepcion, the sky is generally clear, rain does not fall for the seven 



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

 Mr. Brown's Appendix to Fliuders'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 2:5,000 feet. It is probable 

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

 thawed, 



