90S C O ME 
Having the quality of comprifing much ; compendious ; 
extenfive.-—So diffufive, fo comprehenfive, fp catholic a' 
grace is charity, that whatever time is the opportunity of 
any other virtue, that time is the opportunity of charily. 
Sprait. 
COMPREHENSIVELY, adv. In a comprehenfive 
manner. 
COMPREHENSIVENESS, f. The quality of includ¬ 
ing much in a lew words or narrow compafs.—Compare 
the beauty and comprehenji've'nefs of legends on ancient 
coins. Addifm. 
CAMPREIGNAC', a town of France, in the depart¬ 
ment of the Upper Vienne, and chief place of a canton, 
in the diftrifif of Bellac : ten miles north of Limoges. 
To COMPRE'SS, rv. a. [ comprejfus , Lat.] To force in¬ 
to a narrower compafs; to fqueeze together. To embrace. 
—There was in the ifland of Io a young girl comprejfed by 
a genius, who delighted to afiociate with the mufes. Pope . 
Her Neptune eyed, with bloom of beauty bleft, 
And in his cave the yielding nymph compreji . Pope. 
COM'PRESS, f. Bolfters of linen, by which furgeons 
fuit their bandages for any particular part or purpofe. 
gptincy. —I applied an intercipient about the ankle and 
upper part ot the foot, and by comprefs and bandage 
• dreffed it up. Wifemcm. 
COMPRESSIBILITY", f. The quality of being com* 
prcffible; the quality of admitting to be brought by force 
into a narrower compafs. 
COMPRES'SIBLE, adj. Capable of being forced into 
a narrower compafs ; yielding to preflu re, Io as that one 
part is brought nearer to another.—Their being fpiral 
particles, accounts for the elalticity of air; there being 
fpherical particles, which gives free paflage to any hetero¬ 
geneous matter, accounts for airs being comprejjible. Cheyne. 
COMPRES'SIBLENESS,y; Capability of being prefled 
clofe. 
COMPRESSION, f [comprefflo, Lat.] The aft of 
bringing the parts of any body more near to each other 
by violence; the quality of admitting fuch an effort of 
Force as may compel the body compreffed into a narrower 
fpace.—Whenever a folid body is preffed, there is an in¬ 
ward tumult in the parts, feeking to deliver themfelves 
from the comfrejfion, and this is the caule of all violent 
•motion. Bacon. 
Compreflion differs from condenfation as the caufe from 
the effeft, compreflion being the aftion of any force on 
a body, without regarding its effefts ; whereas condenla- 
tion denotes the Hate of a body that is aftually reduced 
into a lefs bulk, and is ah effeft of compreflion, though it 
may be effefted alfo by other means. Neverthelefs, com- 
predion and condenfation are often confounded. Pumps, 
which the ancients imagined to aft by luftion, do in re¬ 
ality aft by compreflion; the pifton, in working in the 
narrow pipe, compreffes the indofed air, fo as to enable 
it, by .the force of its increafed elafticity, to raife the 
valve, and make its efcape; upon which, the balance 
being deftroyed, the preflure of the atmofphere on the 
flagnant iurface, forces up the water in the pipe, thus 
evacuated of its air. 
It was long thought that water was not compreflible in¬ 
to lefs bulk ; and it was believed, till lately, that after the 
air had been purged out of it, no art or violence was 
able to prefs it into lefs fpace. In an experiment made by 
the Academy del C-i men to, water, when violently fqueezed, 
made its way through the fine pores of a globe of gold, 
rather than yield to the compreflion. But the ingenious 
Mr. Canton, attentively conlidering this experiment, found 
that it was not fufiiciently accurate to j u ft if y the conclu- 
fion which had always been drawn from it; Ante the Flo¬ 
rentine philoloplvers had no method of determining that 
the alteration of figure in their globe of'■gold, occalioned 
fuch a diminution of its internal capacity, as was exaftly 
equal to the quantity of water forced into its pores. To 
bring this matter therefore to a more accurate and deci- 
4 
C O M 
five trial, >he procured a fmail glafs tube of about two feet 
long, with a.ball at one end, of an inch and a quarter in 
diameter. Having filled the ball and part of the tube 
with mercury, and brought it exabtiy to the heat of fifty 
degrees of Fahrenheit’s thermometer, he marked the place 
where the mercury flood in the tube, which was about 
fix inches and a half above the ball; he then raifed the 
mercury by. heat to the top of the tube, and there lealed 
the tube hermetically ; then upon reducing the mercury 
to the fame degree of heat as before, it flood in the tube 
i*tfo °f an inch higher than the mark. The lame expe¬ 
riment was repeated with water exhaufted of air, inftead 
of mercury, and the water flood in the tube of an 
inch above the mark. Since the weight of the atmofphere 
on the outfide of the ball, without any counterbalance 
from within, will comprefs the ball, and equally raiie 
both the mercury and water, it appears that the water 
expands -JWj of an inch more than the mercury by remov¬ 
ing the weight of the atmofphere. Having thus deter¬ 
mined that water is really compreflible, he proceeded to 
eftimate the degree of compreflion correfponding to any 
given weight. For this purpofe he prepared another ball, 
with a tube joined to it; and finding that the mercury 
in of an inch of the tube was the hundred thoufandth 
part of that contained in the ball, he divided the tube 
accordingly. He'then filled the ball and part of the tube 
with water exhaufted of air; and leaving the tube open, 
placed this apparatus under the receiver of an air-pump, 
and obferving the degree .of expanfion of the water an- 
fwering to any degree of rarefaftion of the air: and again 
by putting it into the glafs receiver of a condenfing en¬ 
gine, he noted the degree of compreflion of the water 
correfponding to any degree of condenfation of the air. 
He thus found, by repeated trials, that, in a temperature 
of fifty degrees, and when the mercury has been at its 
mean height in the barometer, the water expands one 
part in 21740 ; and is as much comprefled by the weight 
of an additional atmofphere; or the compreflion of water 
by twice the weight of the atmofphere, is one. part in 
10S70 of its whole bulk. Should it be objefted, that the 
comprefiibility of the water was owing to any air which 
it might be iuppofed to contain, he anlwers, that more 
air would make it more compreflible; he therefore let in¬ 
to the hall a bubble of air, and found that the water was 
not more comprefled by the fame weight than before. In 
fome farther experiments of the fame kind, Mr. Canton 
found that water is more compreflible in winter than in 
fummer; but he obferved the contrary in ipirit of wine, 
and oil of olives. The following table was formed when 
the barometer was at twenty-nine inches and a half, and 
the thermometer at fifty degrees. 
Compieflion of 
Millionth parts. 
Spec, grav 
Spirit of wine - - 
- 
■66 - - 
846 
Oil of olives - 
- 
48 - - 
918 
Rain water - - - 
- 
46 - - 
1000 
Sea water - - - 
- 
40 - - 
- 1028 
Mercury - 
- 
3 - - 
- 13595 
He infers that tliefe fluids are not only compreflible, but: 
elaflic; and that the compreflions of them, by the fame 
weight, are not in the inverfe ratio of their denfities, or 
fpecific gravities, as might be fuppofed. The compreflion 
of the air, by its own weight, is lurprifingly great; but 
the air may be (till further comprefled by ai t. This im- 
menfe compreflion and dilatation, Newton obferves, can¬ 
not be accounted for.in any other way, but by a repelling 
force with which the particles of air are endued ; by vir¬ 
tue of which, when at liberty, they mutually fly each 
other. This repelling power, he adds, is Itronger and 
more fenfible in air, than in other bodies ; becaufe air is 
generated out of very fixed bodies, but not without great 
difficulty, and by the help of fermentation: now thofe 
particles always recede from each other with the greateft 
violence, and are compreffed with the greateft difficulty, 
which, when contiguous, cohere the more ftrongly. 
COMPRLS'SURE, 
