| or the virgin soil of forests. 
AMMONIA. 157 
ingly in moderate doses, and in mixture with the | 
carbonaceous matter of the soot, and possessing, 
in large doses, a degree of energetic causticity 
which operates with destructive violence on the 
tender organs of plants. 
Ammonia, in all its manurial action, appears 
to operate best in a state of natural mixture with 
the various ingredients of farm-yard dung, and 
next best in a state of thorough mixture with 
the several vegetable and mineral ingredients of 
a long-wrought arable soil; so that, in order to 
its most beneficial effects being developed, it 
either ought never to be distributed in a sepa- 
rate or concentrated condition, as in that of salts, 
guano, or putrid urine, or ought, previous to dis- 
tribution, to be thoroughly mixed with a large 
proportion of loamy and vegetable soil. The ni- 
trogen which it supplies to plants requires to be 
in combination with certain other elements, in 
order to serve as the most suitable food or the 
peculiar nourishment of animals; and these other 
elements are usually furnished in the most effec- 
tive proportions either by average farm-yard man- 
ure or by a complex and thorough mixation of 
chemical manures with the soil of arable lands 
Ammonia, though 
always useful and often indispensable, does by 
no means require to be in every instance supplied 
to the ground even as an ingredient of farm-yard 
manure, and still less in any such concentrated 
form as that of guano, putrid urine, ammoniacal 
salts, or ammoniacal water; for when any soil, 
whether newly reclaimed from the forest, or en- 
riched by prolonged fallow, or worked into prime 
condition by judicious cropping, contains a sufii- 
cient supply of the other ingredients required 
for combination with nitrogen, the ammonia ob- 
tained from the atmosphere may be perfectly 
ample for every purpose of luxuriant vegetation. 
See Atumina, Azorz, Humus, Manurs, and Foop. 
The action of an artificial supply of ammonia, 
even in the main capacity of this substance as a 
source of nitrogen, is limited, like that of hu- 
mus aS a source of carbonic acid, chiefly to an 
acceleration and rarely to an augmentation in 
the development of our cultivated plants; and 
when the supply is made in any incautious or 
concentrated form, it overstimulates the plants 
to the diminution or exhaustion of their vital 
energy, or even exerts such a caustic power upon 
their roots or foliage as speedily to kill them. 
Any ammonia, exhibited to plants in the form of 
a caustic vapour, is certain to peril their vege- 
tation. Ammoniacal water, such as is obtained 
in the manufacturing of coal gas, though used 
with a highly fertilizing effect in various capaci- 
ties, and particularly as a top-dressing to grass 
lands, yet requires to be employed with consider- 
able caution, and, if administered in too great 
strength, will work utter mischief and disaster. 
This liquid, as procured at the public works, is 
of three different strengths, and might, in any 
instance, have its strength tested by instruments; 
yet it ought never to be applied till so far diluted 
with rain or river water that it will not, when 
tested on a grass sward, farther discolour the 
narrow root-leaves of any of the grasses than 
slightly to lighten the tinge of their verdure. 
Even genuine guano, in spite of its well-estab- 
lished and very great power as a fertilizer, pos- 
sesses such a caustic superabundance of ammoni- 
acal matter, that, if applied to the soil in an 
undiluted state or not well mixed with a very 
large proportion of mineral ingredients, it will 
seriously injure most kinds of plants, and rapidly 
kill not a few. Yet the fixed salts of ammonia, 
particularly the sulphate, the muriate, and the 
phosphate, require, for quite an opposite reason, 
to be thoroughly diluted with foreign matters, or 
administered only as ingrediential parts of com- 
pound manures; for when exhibited in powder, in 
solution with water, or in mixture with only a 
small proportion of soil or other mineral diluent, 
they remain in a chief degree inactive, and are 
but very limitedly absorbed by plants. The true 
cause of their efficiency to any extent in the soil is 
believed by Boussingault to be their reconversion, 
by means of calcareous matter, into carbonate of 
ammonia; and as this reconversion is invariably 
resisted in the laboratory or upon the surface of 
the ground, and takes place only in the peculiar 
and complicated circumstances of their contact 
with other manures and partial exclusion from 
the air in diffusion through the soil, they exert 
their ammoniacal force upon vegetation just or 
very nearly in the degree of their removal from 
an undiluted or unmixed condition. A true 
knowledge of the complicated relations of am- 
monia, will thus tend to fix attention upon it 
chiefly as an ingredient in rain-water and in 
compound manures, and will inculcate extreme 
caution respecting its undiluted or concentrated 
artificial use. 
At a recent meeting of the French Academy 
of Sciences, M. Boussingault made a commu- 
nication relative to a new ammoniacal man- 
ure. Having remarked that magnesia, the basis 
of which has always been regarded as injuri- 
ous to vegetation, was found in the ashes of all 
vegetables, and in a proportion in accord with 
the quantity of phosphorus also found in the 
ashes, and of that of the azote, which enters into 
the composition of plants, he was led to infer 
that vegetables must assimilate with ease and 
advantage the ammoniated-magnesian phosphate. 
Being desirous of verifying this by experiment, 
he planted on the 1st of May last some early 
maize, which had already germinated in two se- 
ries of pots, into the half of which he had poured 
15 grammes (about half an ounce) of double phos- 
phated salt for each pot. The two series of pots 
were then placed in the open ground. During 
the first twenty-five days the vegetation was the 
same with both series; after that there was a 
difference in favour of the pots which had been 
watered with the phosphate. 
On the 25th of 
