130 HOW 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 Baumhauer, 40 to 90 Ee “ ae 
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-Salis—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 
