OF SOUTH CAROLINA. 229 
Or Mawnure_s. 
Every thing, added to the land, that tends to preserve or increase the fertility of the arable soil, 
may be considered a manure. 
It is not necessary to discuss the direct application of those substances to the soil in which it is 
deficient—such as soda, potash, phosphate of lime or bone ash, &c. Under peculiar circumstances, 
such applications are possible, but with us they are generally out of the question, excepting to a 
very limited extent. 
We must use such materials only as are cheap, easily accessible, and that require but little skill in 
the preparation, at the same time that they contain the substances that enter into the composition 
of the crop. In proportion as a manure answers these conditions, it is valuable. 
Modern chemical science has shed a flood of light on the interesting. subject of manures, in all 
its bearings. A few of the most important researches on this subject will be presented here. 
Manures may be divided into two classes: those of organic origin, including animal and vegeta- 
ble substances, and those of mineral origin, or mineral manures. Although organic manures are 
distinguished by the nitrogen which they contain, they also abound in mineral matters of the most 
valuable sorts. That plants may, and do, derive from the atmosphere a large portion of the car- 
bon and other organic elements which they contain, is quite certain ; nevertheless, it is equally true 
that they take up, by the roots, nitrogen and other organic elements, particularly in the young state, 
and before the leaves are fully developed—hence the value of organic manures is estimated by the 
amount of nitrogenized substances they contain, notwithstanding the valuable salts also present in 
them. Hermbsladt has shown, experimentally, that the value of wheat flour, as food, will vary 
with the amount of nitrogen in the substance with which the wheat is manured. 
Of all manures those of animal origin are the most active and most valuable. In the excretions 
of animals there will always be present all the constituents of the food, excepting the portion con- 
verted into flesh, blood, and bone, by nutrition. The former consist of organic matters, and the 
latter of phosphate of lime; so that a corn-fed animal will return to the dung-heap all the ingre- 
dients of the grain, excepting a portion of the organic matter and phosphate of lime ; and so of the 
rest of its food. When we know the chemical composition of the food, the value of the excrements 
may be estimated. Léebig, who has popularised this subject in the most interesting manner, has 
shown that the condition of the animals has great influence on the value of the manures. Lean 
and growing animals extract more from the food than full grown and fat ones, and consequently 
leave poorer manures. 
Carniverous animals that feed upon highly nitrogenised food, have the richest excrements, and 
hence the value of night soil, as a manure, and of guano,* which is composed of the excrements of 
sea-fowls, that feed upon animal matter. A manure, to possess great value, must be complex in its 
* The following is the composition of guano, according to Townes. 
Oxalateiof ammonite te. <ic-).1.'s. 6s -lccmoletacremte ste set 
Bp ate Oe S SOO dae See OOP ae coe Sn doageanddec 66.2 i 
Traces of carbonate of amonia and organic matter. 
Phosphates of lime and of magnesia......-...---.+- e000 29.2 
. Phosphates and alkaline chlorides and traces of sulphates.... 4.6 
