A T M 
AT'LIM, a town of Siberia, on the Oby. Lat. 61. 5. 
N. Ion. 85. o. E. Ferro. 
Atlim, a river of Siberia, which runs into the Oby, 
at a town of the fame name. 
AT'MOSPH ERE,_/i [ atmofphera , Lat. of ar^.'Sc, a va¬ 
pour, and Gr. afphere.] A term ufed to lignrfy 
the whole of the fluid mafs, confiding of air, aqueous and 
other vapours, elettric fluids, Sec. which furrounds the 
earth to a confiderable height, and partakes of all its mo¬ 
tions, both annual and diurnal. 
The compofition of that part of our atmofphere pro¬ 
perly called air, was till lately but very little known. For¬ 
merly it was luppofed to be a Ample, homogeneous, and 
elementary, fluid. But the experiments of Dr. Prieftley 
and others have difcovered, that even the purelf kind of 
air, which they call vital or dephlogiflicated, is in reality 
a compound, and might be artificially produced in various 
ways. This dephlogiflicated air, however, is but a (inall 
part of the compofition of our atmofphere. By accurate 
experiments, the air we ufually breathe, is compofed of 
only one-fourth part of this dephlogiflicated air, or per¬ 
haps lefs; the other three parts, or more, confiding of 
w hat Dr. Prieftley calls phlogijlicated , and M. Lavoifier, in 
tfte new chemiftry, mephitic, air. 
Befides thefe forts of air, it is obvious that the whole 
mafs of the atmofphere contains a great deal of water, to¬ 
gether with the vafl heterogeneous collection of particles 
raifed from all bodies of matter on the furface of the earth, 
by effluvia, exhalations, &c. fo that it may be conlidered 
as a chaos of the particles of all forts of matter confu- 
fedly mingled together. And hence the atmofphere has 
been confidered as a large chemical veil'd, in which the 
matter of all kinds of fublunary bodies is copioully float¬ 
ing; and thus expofed to the continual action of that im- 
menfe furface, the fun ; from whence proceed innume¬ 
rable operations, fublimations, reparations, compolitions, 
digeftions, fermentations, putrefactions, &c. 
There is, however, one Jubilance, namely, the electrical 
fluid, which is very diftinguilhable in the mafs of the at¬ 
mofphere. To meafure the abfolute quantity of this flu¬ 
id, either in the atmofphere, or any other Jubilance, is 
perhaps impoflible : and all that we know on this fubjeCt 
is, that the eleCtric fluid pervades the atmofphere ; that 
it appears to be more abundant in the l'uperiorthan the in¬ 
ferior regions; that it J'eems to be the immediate bond 
of connection between the atmofphere and the water which 
is fufpended in it; and that, by its various operations, the 
phenomena of hail, rain, (now, lightning, and other kinds 
of meteors, are occafioned. See thofe refpeCtive articles ; 
fee alfo the article Aerology. 
The ufes of the atmofphere are fo many and great, that 
it feems indeed abfolutely necelfary, not only to the com¬ 
fort and convenience of men, but even to the exiftence of 
all animal and vegetable life, and to the very conflitution 
of all kinds of matter whatever, and without which they 
would not be what they are : for by it we live, breathe, 
and have our being ; and, by inlinuating it/elf into all the 
vacuities of bodies, it becomes the great fpring of moft 
of the mutations here below, as generation, corruption, 
dilFolution, &c. and without which none of thefe opera¬ 
tions could be carried on. Without the atmofphere, no 
animal could exirt, or indeed be produced; neither any 
plant, all vegetationcealing without its aid; there would 
be neither rain nor dews to moiften the face of the ground ; 
and, though we might perceive the fun and (tars like bright 
fpecks, we Jhould be in utter darknefs, having none of 
what we call day-light, or even twilight: nor would either 
fire or heat exift without it. In fhort, the nature and con¬ 
flitution of all matter w ould be changed, and ceafe; want- 
this univerfal bond and conitituting principle. 
By the mechanical force of the atmofphere, as well as 
by its chemical virtues, many neceflary purpofes are an- 
fwered. We employ it as a moving power, in the motion 
of (hips, to turn mills, and for other fuch ufes. And it 
b one of the great diJcoveries of the modern philofophers, 
Vol.II. No. 83. 
ATM 473 
that the feveral motions attributed by the ancients to a 
fuga vacui, are really owing to the prelfure of the atmof¬ 
phere. Galileo, having obferved that there was a certain 
ltandard altitude, beyond which no water could be eleva¬ 
ted by pumping, took an occalion from thence to call in 
queftion the doCtrine of the fchools, which afcribed the 
alcent of water in pumps to the fuga vacui, and inftead of 
it he happily fubftituted the hypothefis of the weight and 
prelfure ot the air. It was with him, indeed, little better 
than an hypothelis, ftnce it had not then thofe confirmations 
from experiment, -afterwards found out by his pupil Tor¬ 
ricelli, and other fucceeding philofophers, particularly 
Mr. Boyle. 
As to the wholcfomcnefs of atmofpheric air, it is generally 
oh the tops of mountains more falubrious than in pits or ve¬ 
ry deep places. Indeed denfe air is always more proper for 
refpiration, as to the mere quality of denlity only, than 
that which is rarer. But then the air on mountains, tho’ 
rarer, is freer front mephitic vapours than that of pits; 
and hence it has been found, that people can live very well 
on the tops of mountains, even when the air is but about, 
half the denlity of that below. 
M. de Saulfure, in his journey upon the Alps, having 
oblerved the air at the foot, on the middle, and on the 
fummits, of various mountains, obferves, that the air of 
the very low plains feems to be the lefs falubrious ; that 
the air of very high mountains is neither very pure, nor, 
upon the whole, feems fo fit for the lives of men, as that 
of a certain height above the level of the fea, which he 
eftimates to be about 200 or 300 toifes, that is, about 430 
or 650 yards. Dr. White, in the Phil. Tranf. vol.lxviii. 
giving an account of his experiments on air made at York, 
fays, that the atmofpherical air was in a very bad ftate, and 
indeed in the word he had ever obferved it, on the 13th of 
September, 1777 ; when the barometer flood at 30-30, the 
thermometer at 69°; the weather being calm, clear, and 
the air dry and fultry, no rain having fallen for above a 
fortnight. A flight fliock of an earthquake was perceived 
that day. The air of a bed-room at various times, viz. 
at night, and in the morning after Jleeping in it, has been 
alfo examined by various perfons; and it has been gene¬ 
rally found, that after deeping in it the air is lefs pure 
than at any other time. 
Dr. Ingenhoufz likewife lent an account of his expe¬ 
riments, made in the year 1779, upon the purity of the 
air at fea and other parts ; which account was read before 
the Royal Society the 24th of April, 1780, and isinferted 
in the Phil. Tranf. vol. lxx. His firft obfervations were 
made on-board a veflel in the mouth of the Thames, be¬ 
tween Sheernefs and Margate, w here he found that the 
air was purer tlytn any other fort of common air he had 
met with before. He found that the lea-air taken farther 
from the land, viz. betw een the Englilh coalt and Oltend, 
was not fo pure as that tried before; yet this inferior pu¬ 
rity feems not to take place always. The doctor’s gene¬ 
ral obfervations, deduced from his numerous experiments, 
are, “ That the air at fea, and clofe to it, is in general pu¬ 
rer, and fitter for animal life, than the air on the land, 
though it leems to be fubjeCt to fome inconliltency in its 
degree of purity with that of the land: that probably 
the air will be found in general much purer far from the 
land than near the fhore, the former being never JubjeCt to 
be mixed with land-air. 
The doctor in the fame paper tranferibes a journal of 
experiments, fhewing the degree of purity of the atmof¬ 
phere in various places, and under different circumltan- 
ces. The method ufed in thefe experiments was to in¬ 
troduce one meafure of common air into the eudiometer- 
tube, and then one meafure of nitrous air. The moment 
that thefe two forts of elaltic fluids came into contaCt, he 
agitated the tube in the water-trough, and then meaJurcd 
the diminution, expreiling it by hundredth parts of a mea- 
furej thus, when he Jays, that fuch air w as found to be 
130, it ligniries, that, after mixing one meafure of it with 
one of nitrous air, th§ whole mixed, .and the diminifhed 
6 E quantity 
