Agricultural and Horticultural Chemistry. 325 



substances which, according to the views of Liebig, consti- 

 tute the food of plants, are water, carbonic acid, and am- 

 monia; these not only contain the four elements of organic 

 matter necessary for their composition, but contain them in 

 a condition, capable of being assimilated by the organs of 

 plants. In addition to these substances, it is well known 

 that plants absorb others of an inorganic nature, which are 

 obtained wholly from the earth, and therefore, of course, 

 consist of substances existing in the soil, in contact with 

 their roots. From what has been stated it must appear 

 evident, that those manures, which contain those organic 

 and inorganic substances the most and in the best state of 

 being absorbed and assimilated by the organs of plants, are 

 the best, and consequently act the most beneficially; hence 

 the preparation of manures, now becoming such an impor- 

 tant study amongst cultivators of the soil. In fact, it is not 

 so easy as it is generally believed, to prepare a compost 

 perfectly suited to the purposes of the cultivator. It re- 

 quires a knowledge of the component parts and the several 

 qualities of the substances to be mixed; and whoever 

 wishes to prepare the best possible manure, must leave 

 nothing to chance; on the contrary, certain fixed principles 

 must be attended to, and chemistry must be consulted, 

 because it is that science only Avhich can teach us in what 

 substances soil is deficient, and what are to be supplied, if 

 the most abundant crops are to be produced. 



In majiing compost, some general rules are always to 

 be observed, and the chief point to consider is, that no sub- 

 stances are mixed together which act disadvantageously 

 upon each other, or cause the evaporation of the volatile 

 parts; on the contrary, such only are to be brought together 

 as mutually decompose and improve each. Layers of difier- 

 ent materials collected into large heaps, — such as dung, 

 marl, lime, common ashes, the ashes and lye of soap man- 

 ufacturers, loam, clay, gypsum, common salt, bone dust, 

 the refuse of salt works, peat, turf, weeds obtained from 

 fields, meadows and gardens, charcoal, night soil, the 

 sweepings of threshing-floors, — in short, all those materials 

 may be used and converted into the most powerful fer- 

 tilizers, without any of the enriching qualities being lost. 

 Those substances thus brought together, being of little 

 original value as a manure, are, by this means, converted 

 into an excellent fertilizer ; and owing to the powerful aid 



