SOILS AND ALKALI. 
11 
has shown that the electrical current possesses the prop¬ 
erty of acting upon the soil constituents, rendering the 
insoluble ingredients more soluble; besides, it is the most 
active ozone former in nature, and shows its invigorating 
effects upon vegetable and animal life in every recurring 
thunder-shower. 
CHEMICAL PROPERTIES. 
Only very general statements can be made in regard 
to the kinds of plant food required by the different crops. 
Cereal crops feed on silicates, and contain a less amount of 
nitrogen than either root or leguminous crops, but they 
are improved by nitrogenous manure. The phosphoric 
acid is concentrated in the grain, and is the most constant 
of all the constituents of the crop. Root crops contain a 
large amount of potash, and are very exhausting to the 
soil; they take up more nitrogen than the cereals, besides 
other ash constituents, as phosphoric acid. The legumin¬ 
ous crops contain twice as much nitrogen as do the 
cereals, and potash and lime in large quantities, while 
silica is nearly absent. They respond readily to potash 
manures. 
Chemical analysis of the ash of plants reveals the 
character of the mineral matters which they absorb from 
water and soil; the office of each constituent is ascertained 
by what is known as water culture. The plan of the 
operation is quite simple. The seeds are germinated upon 
some clean support, as a sponge or piece of cotton ; they are 
placed in clean glass vessels and the vessels filled with pure 
water, so as to cover the roots. It has been found that if the 
water is pure, only a certain development will be produced ; 
but if, now, certain salts of the elements are added, the plant 
commences to thrive; for instance, potash has been found 
necessary to the formation of starch, and the chloride of 
potash gave the best results. Calcium (lime) has been 
thought to serve as a vehicle for sulphuric and phosphoric 
acid and in fixing the oxalic acid, which is poisonous to 
