i8o STUDIES FOR STUDENTS 



weathering in fact becomes in large measure a climatic phenomenon. In moist 

 and hot regions it is accomplished easily and rapidly; in hot and dry regions 

 it seems to play an unimportant part, and where high degrees of cold prevail 

 even an abundance of water is unable to produce it in any but an insignificant 

 amount. Beneath the ever-moist moss cushions of Finland and the northern Ural, 

 granite shows undecomposed surfaces.' 



Russell, from observations in the southern hemisphere, reaches the 

 same conclusions, his statements being as follows: 



I may remark from observation that in the Kerguelen and Crozet Islands, 

 in the South Indian Ocean, where a cold, humid cHmate prevails, and where not 

 only forests but arborescent growths of every description are wanting, there is 

 but little soil, and nothing approaching terra rossa is to be seen. These islands 

 are formed, probably throughout, of dark basaltic rocks, rich in iron, which under 

 more favorable conditions would yield a deep layer of ferruginous soil. Con- 

 trast with the Kerguelen Islands others of similar origin in the tropics, as the 

 Samoan Islands, for example. On Kerguelen the highest vegetation is a bitter 

 cabbage which grows mostly in sheltered places along the coast, where it is sur- 

 rounded with rhatted ferns and tussocks of moss. The landscape, even on the 

 exceptional days of sunshine, is dark, silent, and gloomy. Among navigators 

 this island is called, not unjustly, the "Land of Desolation." In the Samoan 

 Islands the rank luxuriance of tropical vegetation imparts to the land when 

 seen from the ocean the deep tint of malachite. Wherever the bare earth appears 

 it gleams forth through the overshadowing boughs with a brilliancy that is en- 

 hanced by contrast and gives a dash of Pompeian red to the picture of tropical 

 beauty. The soil is deep and rich, and, as in Bermuda, must have been derived 

 entirely from the decay of the rocks forming the islands, which in this case, how- 

 ever, are basaltic, and agree in many ways with the rocks forming the Kerguelen 

 Islands. 



The contrast between the present condition of the Kerguelen Islands and 

 that of the Samoan Islands has resulted from differences in climatic conditions. 

 This conclusion would have to be modified, perhaps, should it be found that the 

 former had recently been glaciated. There are abundant observations to show, 

 however, that, in general, islands below latitude 50° south, where winter is almost 

 continuous, are desolate, uninhabitable wilds, and that forty degrees nearer the 

 equator, where perpetual summer reigns, lands formed of nearly identical rock 

 have suffered deep decay and are covered with a rich ferruginous soil, which 

 supports a varied and luxuriant tropical flora. ^ 



That rock decay may take place to some extent in cold climates and 

 is frequently absent because of glaciation is indicated by the observa- 



1 Fiihrer jilr Forschungsreisende, Berlin, 1886, p. 100. 



2 Subaerial Decay of Rocks and Origin of the Red Color of Certain Formations, 

 Bulletin 52, U. S. Geological Survey, pp. 30, 31, 1889. « 



