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GEOLOGICAL MEMOIRS. 



tive examination of the waters of two alpine streams, made by M. 

 Adolph Schlagintweit, is here given. 



1. The Moll at Heiligenhlut. 2. The Oetz at Vent. 



37800 grammes of the water 29000 grammes of the 



evaporated. water evaporated. 



Carbonate of lime 0*3182 0*13044 



Carbonate of magnesia. 0*1334 0*00144 



Silica 0*2719 0*25170 



Chloride of potassium 1 n AQOn „ niOKr . 

 Chloride or sodium . J 



Oxide of iron 0*0363 0*37728 



Manganese 0*1221 traces. 



Argilla traces traces. 



Sulphates traces — 



Sand in suspension . . 0*0733 0*24888 



0*9882 1*02230 



Although both of these rivers rise in the crystalline slate range, 

 and resemble each other in the mass of the substances held in solu- 

 tion, yet the above analyses show important differences in the indi- 

 vidual constituents. This is particularly the case with the carbonate 

 of lime and carbonate of magnesia ; the larger proportion of these in 

 analysis No. 1, is due to the general distribution of carbonate of lime 

 in all the rocks of the Upper Moll district, the composition and 

 stratigraphical conditions of which are referred to in Chapter x. ; 

 whilst in the Oetz Valley only a few, quite isolated limestone masses 

 occur. On the other hand, the greater proportion of oxide of iron 

 is present in analysis No. 2 ; and this is always an important product 

 of weathering. The greater proportion of calcareous matter in the 

 Moll-district is of much interest with respect to the series of obser- 

 vations on Alpine vegetation, given by the author in a subsequent 

 chapter of this work. 



The history of the hydrographical phsenomena of the Alps is suc- 

 ceeded by observations on Erosion, having reference to the present 

 effects of rivers as eroding agents, and their relation to the formation 

 of valleys in general ; the sudden emptying of large reservoirs of 

 water ; notices of the course of the great flood (from the bursting of 

 the Vernagt Lake) in the year 1848, with a table, showing the re- 

 markable differences between the time required for the passage 

 through the valley of the great bulk of the flood-water from place 

 to place, and the usual rate of the river-water passing the same 

 places ; the influence of valley-basins on the course of great bodies of 

 water (as seen in the table above referred to) ; the transport of blocks 

 and shingles ; and the collecting of the water of the Alpine lakes. 



The subject of Weathering, or the mechanical disintegration and 

 chemical decomposition of rocks by means of the atmosphere and its 

 precipitations, succeeds, and demands notices of the physical pro- 

 perties of the earth and its composition, of the nature and properties 

 of humus, and of the influence of vegetation on the formation of the 



