CON 
CON 
ling acetate of copper reduced to powder 
in a retort. At first there comes over a 
liquid nearly colourless, and almost insipid, 
and afterwards a highly concentrated acid, 
tinged witli green ; but being distilled a 
second time in a moderate heat it is colour- 
less, transparent, exceedingly pungent and 
concentrated. 4. The most perfect method 
of obtaining this acid in a concentrated 
state, was discovered by Mr. Lowitz, of 
Petersburgh. It is thus : distil a mixture of 
three parts of acetate of potash, and four 
parts of sulphuric acid, till the acetic acid 
has come over into tlie receiver. To sepa- 
rate it from the sulphuric acid, with which 
it is slightly contaminated, it must be dis- 
tilled over a portion of acetate of barytes. 
. CONCENTRIC, in mathematics, some- 
thing that has the same common centre 
with another : it stands in opposition to 
eccentric. Concentric is chiefly used in 
speaking of round bodies and figures, 
or cu'cular and elliptical ones, &c. but 
may be likewise used for polygons, drawn 
parallel to each other upon the same 
centre. Themetliod of Nonius, for gradu- 
ating instruments, consists in describing 
with the same quadrant 4.5 concentric 
arches, dividing the outermost into 90 equal 
parts, the next into 89, &c. 
CONCEPTION, in logic, is the simple 
apprehension or perception which we have 
of any thing,without proceeding to affirm or 
deny any thing about it. There are r^es 
by which we may guide and regulate our 
conceptions of things, which is the main 
business in logic : for most of our errors in 
judgment, and the weakness, fallacy, and 
mistakes of our argumentation proceed 
from the darkness, confusion, detect, or 
some other irregularity in our conceptions. 
The rules are these: 1. To conceive of 
things clearly and distinctly in their own 
natures. 2. Completely in all their parts. 
3. Comprehensively in all their properties 
and relations. 4. Extensively in all their 
kinds. 5. Orderly, or in a proper method. 
■ CONCESSION, in rhetoric, a figure 
whereby something is freely allowed that 
yet might bear dispute, to obtain something 
that one would have granted to him, and 
which he thinks cannot fairly be denied, as 
in the following concession of Dido, in 
Virgil : 
“ The nuptials he disclaims, I urge no 
more; 
Let him pursue the promis’d Latian shore. 
■ A short delay is all I ask him now ; 
A pause from grief, an interval from woe.” 
CONCHIUM, in botany, a genus of the 
Tetrandia Monogynia class and order. 
Calyx none; petals four, supporting the 
stamina ; stigma turbinate, mucrouate ; 
capsule one-celled, two-seeded ; seeds 
w’inged. 
CONCINNOUS, in music, a term gene- 
rally confined to performance in concert. 
It applies to that nice discriminating execu- 
tion in which tlie band not only gives with 
mechanical exactness every passage of 
the composition, but enters into the design 
or sentiment of the composer, and, pre- 
serving a perfect concord and unison of 
eflfect, moves as if one soul inspired the 
whole orchestra. 
CONCHOID, in geometry, the name of 
a curve, given it by its inventor, Nicomedes , 
and is thus generated. 
Draw the right line QQ (see Plate III. 
Miscel. fig. 14.) and AC perpendicular to it in 
tlie point E ;.and from the point C draw many 
right lines C M, cutting the right line Q Q 
in Q ; and make QM = QN, AE=:EF, 
viz. equal to an invariable line : tlien the 
curve, wherein are the points M, is called 
the first conchoid ; and the other, wherein 
are the points N, the second; the right line 
Q Q being the directrix, and the point C 
the pole ; and from hence it will be very- 
easy to make an instrument to describe the 
conchoid. 
The line Q Q is an asymptote to both the 
curves, which have points of contrary flec- 
tion. See Asymptote. If Q M = A E z= 
«, EC = 6, MR = EP = a;, ER=PM 
= y ; then will — ■ 2 6 a: =. 
V 3^ — %h and express the 
nature of the second conchoid; anda:”-}- 
‘Z h -^-y^ ^b^ a? 
a* x^, the nature of tlie first ; and so both 
these curves are of the third kind. 
This curve was used by Archimedes and 
other ancients in the construction of solid 
problems ; and Sir Isaac Newton says that 
he himself prefers it before other curves, or 
even the conic sections, in the construction 
of cubic and biquadratic equations, on ac- 
count of its simplicity and easy description, 
shewing therein the manner of their con- 
struction by help of it. 
CONCHOLOGY. The study of shells, 
or testaceous animals, is a branch of natu- 
ral history, though not greatly useful in hu- 
man economy, yet perhaps by the beau- 
ties of the subjects it treats of, is adapted 
to recreate the senses, and insensibly lead 
to the contemplation of the glory of the 
Divinity in their creation. 
Z 2 
