ELEMENTS OF SOILS. 
223 
great proportion of liquids. The physical constitution of the atmosphere being determined, 
life, its functions, and its apparatus, are adjusted to those conditions. 
Carbon is a solid. The diamond is always referred to as an example of pure carbon, 
because, when burned, the residue is carbon in union with oxygen. The common form, 
charcoal, differs but slightly from the diamond in composition, but the physical properties 
are quite different, although the difference is not greater than that of pure alumina and 
the sapphire. So it is not improbable that, like the instance here cited, the difference is 
due to crystallization. Carbon forms the solid parts of organic bodies, except those which 
are formed of the compounds of lime. In the vegetable kingdom, especially, carbon is 
the element which gives solidity and strength to the individual. It also enters largely 
into the composition of fluids, or it may be said that this state is preparatory to a conver¬ 
sion into the solid form. Carbon is always black when uncrystallized. Chalk and lime, 
magnesia, together with a great number of other bodies of the mineral kingdom, are com¬ 
pounds of carbon, or rather triple compounds of oxygen, carbon, and lime or some other 
base. Carbon is widely distributed in both the organic and inorganic worlds. It is asso¬ 
ciated with the oldest products of the latter, and is brought up from the lowest depths of 
the earth, and hence is as ancient and consequential as any of the elements except oxygen. 
Soil without carbon, very rarely, if ever, produces perfect vegetables. The experiments 
which go to prove the contrary are suspicious. Soil which has been heated to redness 
does not part with its carbon ; the acids do not destroy it; and hence those instances where 
it has been attempted to destroy organic matter, or the carbon in soil, may be set off against 
the difficulty of destroying it under circumstances more favorable. Crenic or apocrenic 
acids are scarcely destroyed by a red heat, when the quantity is very small; so the organic 
matter of soils is very rarely consumed, when brought to a bright redness preparatory for 
analysis. 
Principal compounds of the four preceding elements. 
The compounds which oxygen, hydrogen, nitrogen and carbon, form among themselves, 
are water, air, and carbonic acid. These will be fully treated in this place, as they are 
agents of the highest importance in the economy of life. 
Water. Few substances are anhydrous; although it is necessary to premise that we do 
not here mean to employ the term in its usual sense. Some substances retain water me¬ 
chanically, and, if dried, are truly anhydrous, or without water in their constitution. We 
mean, by the term anhydrous , to specify that condition of substances in which they neither 
contain water mechanically by absorption, nor chemically by combination. We use the 
word with a wider than the usual latitude ; and for this reason, that so far as the welfare 
of either kingdom of nature is involved, the mechanical combination is as important as the 
chemical. 
Nearly four-fifths of the matter of animals is liquid, all of which is lost simply by drying 
in the atmosphere at its natural temperature. Vegetable matter contains less. Wood 
