CARBON, OXYGEN, etc. 
17 
Hardness in well and spring waters is often due to the presence of the compounds of 
chlorine. Chloride of potassium forms an important element of tobacco ; and indeed it 
is somewhat remarkable that both chlorides, that of sodium and that of potassium, exist 
together in such large proportions as they are found in this deleterious weed. One variety 
of tobacco was found by Will and Fresenius to contain 8'53 of chloride of potassium. 
The stalks of hops contain 9'64 per centum. The Saccharum officinarum contains a much 
larger quantity ; amounting, according to Stenhouse, to 30 per centum. 
CARBON, OXYGEN, HYDROGEN AND NITROGEN. 
In various states of combination, these bodies constitute those forms of matter which are 
called organic. The most important, or those which are most generally distributed, are 
carbon and oxygen forming carbonic acid, oxygen and hydrogen forming water, hydrogen 
and nitrogen forming ammonia. In the present constitution of bodies, not one of these 
compounds could be dispensed with : they are universally diffused and present in some 
form or other, in the vegetable, animal and mineral kingdoms. 
Carbonic acid is the source of carbon in plants. It is also the great solvent in nature 
for the hardest materials, such as felspar in granite. Its constant, though slow action, 
compensates for the rapid and powerful action of mineral acids. I have already alluded 
to this property of carbonic acid. 
Water in itself, and as water, must be furnished to all living bodies, and there are but 
few substances in the mineral kingdom which do not require it; but when it is considered 
in its constitution and the decompositions \vhich it is susceptible of, and the changes it can 
effect in other bodies, or in its actions and reactions, its influence and importance are 
exceedingly magnified and extended. The same may be said of ammonia, the great source 
of nitrogen in organized bodies. 
I need not here dwell longer either upon these elements themselves, or upon their com¬ 
pounds*. Of carbonic acid, I would remark in this place, that I have some doubt as to 
the absorption of it by the leaves of vegetables ; and even admitting that it is absorbed, 1 
can not but maintain the position that the roots are the principal organs which convey it 
to the plant. Leaves may condense carbonic acid on their surfaces, without absorbing it. 
It is, however, a point upon which I do not propose to insist. The fact that it is necessary 
that it be supplied by the roots, I have no doubt will be readily admitted ; and hence prac¬ 
tically the materials which are capable of furnishing it, must be supplied where they are 
required. 
* See Vol. I, pp. 223 -227 of the Agriculture of New-York. 
[Agricultural Report-—Vol. ii.] 3 
