propagated from suckers, from cuttings of the 
root, and from foreign seeds ; and the last ought, 
immediately on their arrival from China, to be 
sown, under protecting glasses, in boxes of light 
earth or of sand and peat. Some remarkably 
fine specimens of ailanthus are growing on the 
Duke of Northumberland’s grounds at Sion ; 
and numerous specimens of it, from 30 to 40 feet 
in height, may be seen in many parts of Hng- 
land. Its timber is hard, heavy, and glcssy, 
bears some resemblance to satin - wood, and is 
susceptible of the finest polish. 
AIR. The gaseous fluid which constitutes the 
great bulk or pure portion of the atmosphere, 
and which forms an essential aliment of both 
animal and vegetable life. Hvery known gaseous 
fluid, from about the middle of last century till 
quite a recent period, was chemically called an 
air ; and the gaseous fluid of the atmosphere, in 
order to be distinguished from other gases, was 
called atmospheric air. The principal airs known 
to the chemists of the last generation were vital 
air, or empyreal air, or dephlogisticated air, now 
called oxygen; phlogisticated air, now called 
nitrogen or azote ; nitrous air, now called nitric 
oxide and deutoxide of nitrogen; dephlogisti- 
cated nitrous air, now called nitrous oxide and 
protoxide of nitrogen ; inflammable air, now 
called hydrogen ; fixed air, now called carbonic 
acid ; and alkaline air, now called ammonia. 
The atmospheric air—the only body to which 
the name air is now with any propriety applied— 
‘consists of oxygen and nitrogen, in the propor- 
tion of one atom of oxygen and two atoms of 
nitrogen, or of two grains of oxygen and seven 
grains of nitrogen, or of one cubic inch of oxygen 
with four cubic inches of nitrogen. This propor- 
tion—which ,we have thus stated in the three 
forms of atom, weight, and volume—is usually 
represented in the form of 20°82 per cent. of 
oxygen, and 79°16 per cent. of nitrogen. A won- 
derful fact—beautifully illustrating both the wis- 
dom of the Creator and the benign care of his 
government—is that this proportion, so far as 
has been ascertained, prevails in all parts of the 
atmosphere,—that, in spite of the enormous con- 
sumption of oxygen in the processes of breathing, 
combustion, putrefaction, oxidation, and acidifi- 
cation, a universal provision exists for restoring 
volumes of it equal to the quantities consumed, 
—that notwithstanding the vastly greater con- 
sumption of it in some places than in others, an 
universal agency is in operation for maintaining 
the fair balance, or the equal diffusion of it in all 
localities of the earth and at all heights in the 
atmosphere,—and that, in defiance of an abun- 
dant and irregular ascent of ammonia, carbonic 
acid, miasmata, and other poisonous matters from 
almost all parts of the material surface of the 
world, chemical and meteorological appliances 
are everywhere at work to prevent these matters 
—except in small localities for the punishment 
of human filth, or indolence, or wickedness—from 
I. 
so accumulating as either to alter the air’s com- 
position or to impair its vital action. Yet though 
the air itself, or pure air, never and nowhere 
sensibly varies in the proportions of its constitu- 
ent oxygen and nitrogen, it is universally subject 
to two admixtures, and locally liable to numer- 
ous deteriorations, which more or less modify its 
power over vegetables and animals. Carbonic 
acid is generally mixed with the air in the pro- 
portion, by weight, of about one part. to a thou- 
sand; and this ingredient is, on the one hand, 
continually abstracted or drunk up by plants for 
assimilation into a main ingredient in their bulk, 
and is, on the other hand, as constantly evolved 
from numerous processes and degrees of animal 
and vegetable combustion and decay; and wher- 
ever, from want of ventilation or from confine- 
ment of the processes which evolve it, or from 
enormous local disproportion between these pro- 
cesses and those which consume it, or from any 
other causes kept in operation by the folly or 
carelessness or sin of man, it is allowed to form 
any considerable local accumulation, it totally 
overpowers the salubriousness of the air, and 
proves most noxious to every kind of animal. 
Watery vapour is everywhere suffused through 
the air, usually or averagely in the proportion, 
by weight, of about one part to an hundred; and 
the increase or the diminution of its quantity 
very sensibly affects the weight and the other 
mechanical conditions of the air, and modifies its 
action considerably on animals and very greatly 
on vegetables. 
acid and aqueous vapour, are so universally pre- 
sent in the air, and so uniformly coactive with it 
in its agency, as to be often considered as belong- 
ing to its constitution; and they really are ex- 
traneous to it, or must be considered as foreign 
matters, chiefly on account of their proportions 
being fluctuating while those of the oxygen and 
the nitrogen are uniform. But the deteriorating 
substances which rise into admixture with the 
atmosphere, directly from the presence of ani- 
mals, from the crowdedness of human population, 
and from the filthy habits, the manufacturing 
processes, the culpable negligence, and the wicked 
conduct of man, are, in all respects, foreign sub- 
stances; and by a singular law which strongly 
illustrates the doctrine of a moral providence— 
they have power to become less or more noxious 
or fatal almost exactly—perhaps quite exactly— 
in the degree in which they arise from the ani- 
mal corruptibility or from the moral delinquency 
of man. Thus, ammoniacal gases, which arise 
merely from animal decay, however large a pro- 
portion they bear to the air in large cities, sel- 
dom of themselves exert any noxious influence, 
but, on the other hand, contribute largely to the 
most valuable processes of vegetation; while the 
miasmata which arise in company with the am- 
moniacal gases from scenes of filthiness and care- 
lessness, the exhalations which ascend from stag- 
nant ponds and undrained marshes, and the gases 
G 
These two substances, carbonic | 
