OF ARTIFICIAL MANURES. 159 



and energetic decay, will benefit plants in the first 

 year of their application ; those, again, that are sol- 

 uble in acids, or decay with less readiness, not till 

 the second or third ; and those, lastly, that are 

 wholly insoluble, or decay still more slowly and with 

 greater diflficulty than the preceding, cannot be ab- 

 sorbed by plants till a still later period. For this 

 reason, analysis may properly arrange these articles 

 of manure in three distinct classes : 1st. Substances 

 soluble in water ; 2d. Substances soluble in acids j 

 3d. Substances insoluble in water and in acids ; — 

 because the farmer is thereby placed in a position to 

 deduce for himself a tolerably correct conclusion re- 

 specting the time and duration of the effect to be 

 expected. To this rule, however, such manures as 

 are composed principally of undecayed or undecom- 

 posed vegetable or animal matters form an excep- 

 tion ; they do not become soluble, and consequently 

 capable of being absorbed by plants, until they have 

 undergone the process of decay. Rape-meal, bone- 

 dust, and woollen rags, for example, contain but few 

 elements, the latter none whatever, that are soluble in 

 water ; yet a great error would be made in pronoun- 

 cing them collectively manures of very slow opera- 

 tion. In such cases, practical experiments must de- 

 cide, and it will soon be shown that rape-meal passes 

 readily, bone-dust with less facility, and woollen rags 

 with still greater difficulty, into decay. If bones are 

 made easily soluble by means of an acid, or rags by 

 means of lye (that is, water saturated with an alkali), 



