404 NOTES ON THE GEOLOGY 



1'593.6 grains were evaporated, and left a residuum of salts 

 equal to 325.0 grains ; which, in 500 grains, would be 102.1 

 grains. 



I have met with no analysis of the water of this lake, except 

 one by Dr. Marcet ; and, as he possessed but a very small quan- 

 tity of it, I thought it desirable to repeat the process. 



In five hundred grains of the water, I find 



Grains. 



Chloride of calcium, ...... 0.74 



Chloride of magnesium, .... 5.76 



Chloride of sodium, ...... 90.53 



Sulphate of soda, . . . . . . 5.67 



102.75 

 Amount of salts by evaporation in 500 grains, . 102.10 



Excess, 65 



This excess is of course to be imputed to errors of analysis. 

 Had time permitted, I should have repeated the process more 

 frequently than I have done. Dr. Marcet gives the result of his 

 analysis of five hundred grains by merely stating the precipitates 

 produced by certain reagents, as follows : 



Grains. 



Muriate of silver, 111.5 



Sulphate of barytes, ...... 66.0 



Phosphate of magnesia, ..... 10.5 



I have not reduced the above analysis so as to compare it ac- 

 curately with my own. But it is obvious to inspection, that he 

 found considerably more sulphuric acid in this water than I did. 

 I ought to mention a fact, however, that may account for tliis 

 difference, without imputing it to errors of analysis. When I 

 first received the water, it was so strongly impregnated with 

 sulphureted hydrogen as to tarnish silver at once. Now must 

 not this gas have resulted from the decomposition of the sulphates 

 in the water ? If so, as Dr. Marcet mentions nothing of the 

 kind, it may (wplain the smaller quantity of sulphates which I 

 was able to find. Again, the specimen which I analyzed was 



