130 IIOM^ CROPS FEED. 



by no means fully charged with carbonic acid, and their 

 solvent effect is much less than that exerted by water sat- 

 urated with this gas. 



The quantity (by volume) of carbonic acid in 10,000 

 parts of rain-water has been observed as follows: Accord- 

 ing to 



Locality. 

 Lampadius, 8 Country near Freiberg, Saxony. 



Mulder, 20 City of Utrecht, Holland. 



Von Buumbauer, 40 to 90 " " " " 



Peligot, 5 ? 



The quantities found are variable, as might be expected, 

 and we notice that the largest proportion above cited does 

 not even amount to one per cent. 



In river and spring water the quantities are somewhat 

 larger, but the carbonic acid exists chiefly in chemical com- 

 bination as bicarbonates of lime, magnesia, etc. 



In the capillary water of soils containing much organic 

 matters, more carbonic acid is dissolved. According to a 

 single observation of De Saussure's, such water contains 

 2"! „ of the gas. In a subsequent paragraph, p. 221, is 

 given the reason of the small content of carbonic acid in 

 these waters. 



The weaker action of these dilute solutions, when con- 

 tinued through long periods of time and extending over 

 an immense surface, nevertheless accomplishes results of 

 vast significance. 



Solutions of Alkali-Salts. — Rain-water, as we have 

 already seen, contains a minute quantity of salts of am- 

 monia (nitrate and bicarbonate). The water of springs 

 and rivers acquires from the rocks and soil, salts of soda 

 and potash, of lime and magnesia. These solutions, dilute 

 though they are, greatly surpass pure water, or even car- 

 bonated water, in their solvent and disintegrating action. 

 Phosphate of lime, the earth of bones, is dissolved by 

 pure water to an extent that is hardly appreciable ; in 



