290 



THE CANADIAN NATURALIST. 



[Aug. 



which drain surfaces covered with decaying vegetation and decom- 

 posing silicates, from both of which they derive dissolved silica. 

 Such waters contain but small amounts of solid matters, but the 

 proportion of silica is relatively considerable, amounting, as we 

 have seen in the water of the Ottawa River, (which contains in 

 10,000 parts, 0-6116 of solid matters), to 0-2060, or thirty-two 

 per cent. ; while in the St. Lawrence, which contains for the same 

 amount of water, 1*6056, the silica equals -3700, or twenty-four 

 per cent, of the solid ingredients. The analysis by H. Deville of the 

 river-waters of France show, in like manner, large amounts of 

 silica, which seem to have been hitherto overlooked in the analyses 

 of most chemists. (Ann. de Chim. et Phys. [3], xxiii, 32.) 



It will be seen by a reference to the tables of analyses given in 

 the second part of this paper, that in the waters of the second class 

 the amount of silica is equal to from 0*15 to 60 parts for 100-00 

 of solid matter. In the alkaline waters of the third and fourth 

 classes its proportion is greater, and up to a certain point appears 

 to increase with that of the carbonate of soda. In the following- 

 table the proportions of carbonate of soda and silica for 10000 parts 

 of solid matters are given for certain springs, whose analyses will be 

 found in tables in and iv : 



The amount of silica which these waters contain does not in any 

 case exceed one or two ten-thousandths, and it is well known that 

 water at the ordinary temperature may dissolve very much more 

 than this amount of silica, even in the presence of alkaline chlorids 

 and of bicarbonates. 



§ 70. Inasmuch as carbonic acid, according to Bischof (Chein. 

 Geol. i, 2), decomposes not only the silicates of soda, but those of 

 lime and magnesia when they are in solution, it might be supposed 

 that the silica in the above waters exists either in a free state or as 

 a soluble silicate with a great excess of acid. The latter view, 

 especially in the case of magnesia, is rendered probable by nume- 

 rous experiments which I shall describe in another paper, 

 which form a part of the series already mentioned in § 41. From 



