XI HEIGHT OF SNOW-LINE 259 



ledonous plants ; large and elegant ferns are numerous, and 

 arborescent grasses entwine the trees into one entangled mass 

 to the height of thirty or forty feet above the ground. Palm- 

 trees grow in lat. 37° ; an arborescent grass, very like a 

 bamboo, in 40° ; and another closely allied kind, of great 

 length, but not erect, flourishes even as far south as 45° S. 



An equable climate, evidently due to the large area of sea 

 compared with the land, seems to extend over the greater part 

 of the southern hemisphere ; and as a consequence, the vegeta- 

 tion 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 arbor- 

 escent fern was found by Forster in New Zealand in 46°, where 

 orchideous plants are parasitical 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 : — 



Latitude. 



Equatorial region ; mean result 

 Bolivia, lat. 16° to 18° S. . . 

 Central Chile, lat. 33° S. . . 

 Chiloe, lat. 41° to 43° S. . . 



Tierra del Fuego, 54° S. . . 



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 



1 See the German Translation of this Journal : and for the other facts Mr. 

 Brown's Appendix to Flinders's Voyage. 



of Snow-line. 



UDserver. 



15,748 



Humboldt. 



17,000 



Pentland. 



14,500 to 15,000 



Gillies, and the Author 



6000 



Officers of the Beagle 





and the Author. 



3500 to 4000 



King. 



