352 TliAKSACTIO.YS OF TUE AMEUICAN IxSTTTVTE. 



may do by assisting the water to better dissolve the mineral consti- 

 tuents, of which we will s[)eak further hereafter. To consider in 

 succession the three subdivisions of that class of fertilizers which 

 furnish plant food, we may speak first of those which are characterized 

 by their comparative abundance of ammonia, a substance that in 

 solution is known bj* the common name of hartshorn, which was given 

 to it because it was first obtained by distilling the horns of harts or 

 deer. It is obtained most abundantly from the decomposition of 

 animal matter ; it is alkaline in its nature, and consequently combines 

 with acids to form salts, and has a strong affinity for water, the latter, 

 at a temperature of sixty degrees, being capable of absorbing 

 ninety times its volume of ammoniacal gas. The ammonia in a state 

 of solution, being absorbed by the roots, is carried upward and 

 decomposed in the interior of the plant, and contributes to the forma- 

 tion of the albuminous matter in the woody portions, and in some plants, 

 as, for instance, in peas and other leguminous ones very materially 

 to the constituents of the seeds. Ammonia may exist in the soil in 

 solution as just mentioned, or it may be in combination with various 

 acids, and consequently in an inert condition, or it may be absorbed 

 by humns or vegetable matter in the soil, which has a strong affinity 

 for it. These conditions should be kept in mind as of great import- 

 ance, not onh' with regard to the branch of the snbject of which we 

 are now speaking, but with reference to the action of lime, potash 

 and other strong alkaline agents which .we shall have occasion to 

 mention further on. For practical purposes artificial ammoniacal 

 manures may be classed as guano, too well known to require minute 

 description here, and divided by agriculturists into ammoniated and 

 phosphatic guano, according as the ammonia or phosphoric acid pre- 

 ponderates in its composition. The materials resulting from the 

 composting of animal matter with snbstances capable of absorbing 

 or neutralizing their ammonia, as in the so called poudrettes, and the 

 products obtained by tho combination of other substances with the 

 ammoniacal liqnors produced in various manufacturing processes, 

 amono- which may be named the chemical compound sulphate of 

 ammonia, which has been stated to have been employed in England 

 with considerable success. The value of each and all of these, from 

 the standpoint from which we are now looking, must be estimated 

 according to their relative proportions of ammonia and the readiness 

 with which the same may be brought into a state of solution in the 

 soil. Guano has been used as a fertilizer in Peru from the earliest 



