Dire 
124 
alkali exists in it, rather as silicate, as in leached 
ashes. Anthracite coal ashes contain carbonate 
of lime, alumina, and oxide of iron; and it is 
good, so far as these abound. 
“The nitrates, or second class of nourishing 
salts, include not only saltpetre, both Hast In- 
dian and South American, or nitrate of potash 
and nitrate of soda, but also all composts of lime, 
alkali, and animal matter. These produce am- 
monia, which, without the lime would act on 
geine, and render that soluble. Ammonia, by 
the mere act of presence, hastens decay; but 
without the influence of lime, ammonia is changed 
to a nitrate of that base, or to nitrate of am- 
monia, Thus in a compost of animal matter 
without alkaline bases, not only has not all the 
geine been rendered as soluble, as is usually sup- 
posed, by the action of ammonia, but the absence 
of alkali has caused the ammonia, before its full 
action has occurred on the organic matter, to be 
converted into a nitrate of that base. But if the 
lime excecds that which the nitric acid can 
saturate, then the soluble geine is seized upon, 
and becomes inert. Nitrates act under the in- 
fluence of the growing plant, the base let loose 
acts on geine, the acid is decomposed, and nitro- 
gen given up to the plant, and it becomes one of 
their essential elements. The elements of nitrate 
of ammonia are all taken up, both acid and base. 
_ If there are any salts which can be called vege- 
table food, they are the nitrates. The imme- 
diate effects of saltpetre or of any other alkaline 
nitrate are due to the liberated alkali, acting on 
the geine; and its permament effects, for experi- 
ence has proved permanency of effect peculiarly 
due to nitrates, are owing to the liberation of an 
immense dose of oxygen, which is produced from 
the gradual decomposition of the acid. Now 
the insoluble geine condenses this in its pores, 
like charcoal. This condensation, like that of 
gas by charcoal, produces heat; it is like fer- 
menting manure, while the condensed oxygen 
acts slowly on the geine, forming carbonic acid. 
It has upon the geine, buried in the soil, the 
same effect that tillage would have, rendering it 
soluble, with this additional advantage, —that 
its carbonic acid instead of escaping acts on the 
silicates. New portions of alkali are thus liber- 
ated, supplying for years that which was first 
applied, as a part of the saltpetre. The nitrates 
then, hold the very first place among salts, in 
agriculture. 
“The phosphates—or third class of nourishing 
salts—include bones, horn, hair, nails, hoofs, 
and claws, and a large portion of the salts found 
in the liquid excretions of animals, These act 
much like nitre, the acid forming a constituent 
of the plants. It is not probable that the acid 
in this class is decomposed. It has not yet been 
proved that carbonates and nitrates exist already 
formed except in a very few plants. The quantity 
of salts which may be applied, will be greatest in 
the carbonates, next in the nitrates, and thirdly 
SALT. 
in the phosphates. The quantity of any salt which 
may be used will, after the largest amount, which ' 
can be safely employed has been ascertained, de- 
pend upon the farmer’s ability to produce it. 
Carbonate of lime may be used to any extent, 
according to the farmer’s idea of its value. Car- 
bonates of alkali may be used with benefit. The 
largest quantity which has been known to be 
used without injury, has been 53 bushels of ashes 
per acre, which are equal to 240 lbs. of potash. 
The quantities used must be determined by ex- 
periment, and perhaps when the largest amount, 
which has been stated, is taken for a new start- 
ing point, the ultimate quantity will be found 
limited only by the geine in the soil, or applied 
in conjunction with the salt. 
‘Tf we now turn to the other division of salts, 
the poisons, that is those whose acid forms but a 
small portion of the elements of plants, we find 
two classes,—first, sulphates, as gypsum, cop- 
peras, Glauber’s salt, all of which in small quan- 
tities are beneficial. An explanation, which at- 
tributes the action of sulphate of lime or plaster, 
to its power of decomposing and fixing in soil 
carbonate of ammonia ought to show, first, the 
actual presence of that salt in air,—second, that — 
sulphate of ammonia is not decomposed by the 
resulting carbonate of lime in the cold,—and third, 
that common salt would, in equivalent quantity 
with plaster, produce equally good effects. It 
never has, and therefore this explanation is not 
correct.—Secondly, muriates or chlorides, as they 
are strictly called, as common salt, muriate of 
lime, bittern, spent ley from soap-works. Com- 
mon salt has been found beneficial when applied 
at the rate of 30 bushels per acre; and at 14 
bushels per acre, was found to produce effect 
next best to 53 bushels of ashes per acre; but 
quick lime at 26 bushels per acre on the same 
land, produced no good result. 
“In all this action of salts, it is seen that the 
presence of life seems almost essential. What- 
ever the vital principle be, it may be best re- 
presented as analogous to electricity and galvan- 
ism. In this point of view, the salts present 
themselves in a new relation,—in a relation, in 
which alone, they may be said to be stimulants 
or excitants. Plants and soil act, it may be sup- 
posed, for illustration, by forming galvanic bat- 
teries or piles with each other. The most active 
element in the pile is the growing plant. It is 
an acknowledged fact, that chemical action, 11 
not the source is ever attended by electrical ef- 
fects. An acid, in contact with an alkali, or 
metal, always produces chemical action ; but the 
silicates of the soil are already combinations of 
acid and metals; hence as such, they have no 
tendency to act on each other. If there be added 
to these a salt or an acid, chemical action, de- 
composition begins. The electricity is, we may 
say, excited by salts—they are in this sense, and 
in no other, excitants or stimulants. The very 
first act of vegetation, the germination of seeds, 
