N. MATERIA MEDICA, THERAPEUTICS, AND HYGIENE. 553 



RELATION OF EARTH STRATA TO THE COMPOSITION OF 



WATERS. 



Dr. List has been prosecuting some inquiries in reference 

 to the variations in composition of spring and river water, iu 

 the course of which he comes to the following conclusions : 

 First, the qualitative and quantitative composition of the 

 water and its physical peculiarities are dependent upon the 

 characteristics of the strata in which the water originates. 

 Second, that the amount of carbonic acid is greater in springs 

 rising in limestone districts, or which pass through limestone 

 strata, than in those from sandstone formations. Third, that 

 the amount of carbonic acid is, in some degree, dependent 

 upon the temperature of the water. Fourth, that the amount 

 of inorganic residuum varies in very narrow limits, and is 

 greater in autumn than in spring. Fifth, that the amount 

 of this residuum, and that of carbonic acid, have no direct re- 

 lation to each other. Sixth, that the total degree of hard- 

 ness is in proportion to the amount of ash ; the temporary 

 hardness to the amount of carbonic acid, this being greater 

 in autumn than in spring. Seventh, that the rain -tall in- 

 creases the amount of ash in spring w 7 ater, wherever there is 

 soluble material in the soil to be w r ashed out, and this in di- 

 rect ratio to the amount of rain-fall. Eighth, that nitric acid 

 is specially discernible in water after a heavy rain, and after 

 great cloudiness and thundery weather. Ninth, that ammo- 

 nia and nitric acid occur when the falling; rain filters through 

 into water in elevated ground. Tenth, that the occurrence 

 of organic material is independent of the occurrence of the 

 fixed constituents. Eleventh, wood and other similar bodies 

 furnish to running water no increase of nitric acid; on the 

 other hand, they supply rich quantities of oxidizable com- 

 binations and greater quantities of ammonia. Stiidicn zur 

 Statistic der Wassei\ E. Zist, 1872, 50. 



ACTION OF SALT AND POTASH SALTS ON THE SYSTEM. 



Careful study was made by Bunge of the remarkable fact 

 that herbivorous animals, domestic as well as wild, exhibit a 

 necessity for salt beyond the amount in their natural food, 

 while the carnivorous do not, although the latter do not ob- 

 tain any more in their ordinary nutriment. Also that, while 



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