CON 
COM 
the glass thus filled under the receiver of an 
air-pump ; and on exhausting the receiver, 
which removed the pressure of the atmos- 
phere from over the water and the glass 
vessel which contained it, in consequence of 
which the water rose a little way into the 
tube, viz. expanded itself. He then placed 
the apparatus under the receiver of a con- 
densing engine, and on forcing the air into 
it, which increased the pressure upon the 
water, a diminution of bulk evidently took 
place ; the water descending a little way 
within the tube. “In this manner,” Mr. 
Canton says, “ I have found by repeated 
trials, when the heat of the air has been 
about 50“, and the mercury at a mean height 
in the barometer, that the water will ex- 
pand and rise in the tube by removing the 
weight of the atmosphere, one part in 
21740, and will be as much compressed 
under the weight of an additional atmos- 
phere. Therefore the compression of water 
by twice the weight of the atmosphere is 
one part in 10870.” “ Water has the re- 
markable property of being more compres- 
sible in winter than in summer, which is 
contrary to what I have observed both in 
spirits of wine and oil of olives.” By the 
same means, and in the same circumstances, 
Mr. Canton ascertained the property of be- 
ing compressed in some otlier fluids, and 
the results are as in the following table : 
Millionth part. 
Compression of spirit of wine... 66 
oil of olives 48 
rain water 46 
sea water 40 
mercury 3 
COMPTONIA, in botany, so called in 
honour of Henry Compton, Lord Bishop of 
London, a genus of the Monoecia Triandria 
class and order. Essential character : male, 
ament, calyx two-leaved; corolla none; 
anthers two-parted. Female ament, calyx 
sixleaved; corolla none; styles two; nut. 
ovate. There is but one species, viz. C. as- 
plenifolia, fem-leaved Comptonia, a native 
of North America. 
COMPUTATION of a planet's motion. 
See Planet. 
Computation, in law, is used in respect 
of the true account or construction of time, 
so understood as that neither party, to an 
agreement, &c. may do wrong to the other ; 
and that the determination of time be not 
left at large, or taken otherwise than ac- 
cording to the judgment and intention of law. 
If a lease is ingrossed, bearing date Ja- 
nuary 1,1808, to have and to hold for three 
years from henceforth, and the lease is not 
executed till the second of January ; in this 
case the words from henceforth shall be ac- 
counted from the delivery of the deed, and 
not by any computation from the date. 
And if the lease be delivered at four o’clock 
in the afternoon on the said second day it 
shall end the first day of January, in the 
third year ; the law, in such computations, 
rejecting all fractions or divisions of the day. 
CONCAVE, an appellation used in speak- 
ing of the inner surface of hollow bodies, 
but more especially of spherical ones. 
Concave glasses, such as are ground hol- 
low, and are usually of a spherical figure, 
though they may be of any other, as para- 
bolical, &c. All objects seen through con- 
cave glasses appear erect and diminished. 
CONCENTRATION, in chemistry, the 
act of increasing the strength of fluids,which 
are rendered stronger by abstracting a por- 
tion of the mere menstnium. This is generally 
effected by evaporation, where the menstru- 
um is driven off at a lower heat than is re- 
quired to drive off the substance with which 
it is united. Thus, dilute sulphuric acid may 
be considered as a mixture of the real acid 
with water ; and by applying a certain heat 
the water may be evaporized, leaving the 
acid behind in a state of concentration. 
When concentrated as much as possible, its 
specific gravity is about twice as great as 
that of water ; but it can rarely be obtained 
denser than 1.85. Wlien concentrated to 
2.000 it contains a considerable portion of 
water, as has been proved by combining it 
with barytes or potash, in which case water 
remains behind, and does not enter into the 
combination. Again, vinegar consists of an 
acid and water, and brandy of alcohol and 
water ; and in proportion as the acid and 
alcohol are freed from the water, they are 
said to be more or less concentrated. This 
may be performed, (1.) either by simple 
distillation, in which case the acid or spirit 
comes over first, leaving the water behind ; 
or, (2.) by exposing the vinegar or brandy 
to severe frost, when the water will be 
frozen, and the acid or alcohol will be found 
in a state of concentration in the middle of 
the ice ; the greater the cold the higher the 
state of concentration. M. Lowitz has 
found that the acid, however concentrated, 
congeals at 22°. Sulphuric acid, on the 
other hand, exposed to a much less severe 
cold crystallizes, and to effect this it must not 
be greatly concentrated. 3. Another mode 
of concentrating the acetic acid is by distil- 
