88 PRINCIPLES OF GARDENING. [CH. II- 



bodies of the first importance to the cultivator of the 

 soil, yet of the economy of which he is generally most 

 ignorant, inasmuch as that their judicious employ- 

 ment requires considerable chemical acquirements. 

 Eyery substance increasing the fertility of a soil, 

 when incorporated ^^ith it, is a manure ; henc^, 

 the earths, when applied to regulate its retentive 

 powers, are actually manures. Manures are ani- 

 mal, vegetable, and mineral ; they directly assist 

 the gro^\i:h of plants ; first, by entering into their 

 composition ; secondly, by absorbing and retaining 

 moisture from the atmosphere ; thirdly, by absorbing 

 the gases of the atmosphere ; fourthly, by stimu- 

 lating the vascular system of the plants. Manures 

 ajjproximately assist vegetation : firet, by killing 

 predatory vermin and weeds ; secondly, by pro- 

 moting the decomposition of stubborn organic re- 

 mains in the soil ; thirdly, by protecting incumbent 

 plants from violent changes of temperature. 



AH these properties seldom, if ever, occur in one 

 species of manure, but each is usually particularized 

 by possessing one or more in a superior degree. 

 That is the most generally applicable manure which 

 is composed of matters essential to the growth of 

 plants ; the chief of these are carbon, hydrogen, and 

 oxygen; therefore all animal and vegetable sub- 

 stances ai'e excellent manui'es. It would evidently 



