30d M. Marchand on Natural Waters. 



density of the water is also strongest, and their richness in 

 saline principles most considerable. A sudden variation in 

 temperature produces also a considerable variation in the 

 constitution of the water. 



9M, We knew before this time the influence of the clear- 

 ing of forests upon the abundance or the scarcity of springs. 

 We had never, however, reckoned upon the influence of vege- 

 tation in general, and, particularly, of the influence of the cul- 

 tivation of agricultural plants upon these same phenomena. 

 It is generally believed that springs are more abundant in 

 winter than in summer. This opinion is erroneous ; it re- 

 sults, from my observations, that, in limestone formations 

 at least, the springs are more abundant when vegetation 

 is most active, and that they decrease in importance in pro- 

 portion as vegetable life is extinguished. They are at their 

 minimum of production about the 15th or 20th of January. 



lOM, All our water, of springs, of brooks, and of rivers, 

 contain azotes ; and, nevertheless, the water of the sea which 

 receives these diJOferent fluids does not contain appreciable 

 traces of these salts. This may be accounted for, on the one 

 hand, from the influence of the respiration of fishes ; the 

 azotes contained in water, in passing with it through their 

 gills, undergoes a decomposition of which the result is am- 

 moniacal. On the other hand, in the depths of the ocean, a 

 considerable quantity of univalve and bivalve mollusca are 

 found (oysters, mussels, &c.), which continually excrete a 

 certain quantity of free sulphuretted hydrogen, which, in its 

 nascent state, ought still to convert to the ammoniacal state 

 the nitric acid of the azotes with which it is in contact. The 

 mud and slime deposited by the waters contain crystals of 

 ammonico-magnesian phosphates, and the waters contain 

 hydrosulphuric acid. 



Wth, Hydrosulphuric acid, free or combined, is also often, 

 if not always, found in rain water. It is this principle which 

 supplies with sulphur the plants belonging to the cruciferous 

 family. 



12thy From this last fact, it results that those localities 

 which are infected by hydrosulphuric acid, may be purified 

 therefrom by the cultivation of plants belonging to this 

 family. 



