C E M 
C E N 
CEN 
318 
a good fitting of large pieces of iron-work, 
which renders it necessary sometimes to join 
anti separate the pieces repeatedly, before a 
proper adjustment is obtained. When this 
is expected, the white lead ought to predo- 
minate in the mixture, as it dries much slower 
than the red. A workman, knowing this 
fact, can be at little loss in exercising his own 
discretion in regulating the quantities. It is 
safest to err on the side of the white lead, as 
the durability of the cement is no way injured 
by it, only a longer time is required for it 
to dry and harden. When the fittings will 
not admit easily of so thick a substance as 
flannel being interposed, linen may be substi- 
tuted, or even paper or thin pasteboard. 
This cement answers well also for joining 
broken stones, however large. Cisterns built 
of square stones put together with this ce- 
ment, will never leak, or want any repairs. 
In this case the 'stories need not be entirely 
bedded in it: an inch, or even less, of the 
edges that are to lie next the water, need 
only be so treated; the rest of the joint may 
be 'filled with good lime. 
Another cement that will stand the action 
xf boiling water' and steam . — This cement, 
which is preferable even to the former for 
steam-engines, is prepared as follows: Take 
.two ounces of sal ammoniac, one ounce of 
flowers of sulphur, and 16 ounces of cast-iron 
filings or borings. Mix all well together by 
rubbing them in a mortar, and keep the pow- 
der dry. 
When the cement is wanted for use, take 
one part of the above powder, and twenty 
parts of clean iron borings or filings, and 
blend them intimately by grinding them in a 
mortar. Wet the compound with water, and 
when brought to a convenient consistence, 
apply it to the joints with a wooden or blunt 
-spatula. By a play of affinities, which those 
who are at all acquainted with chemistry will 
be at no loss to comprehend, a degree of ac- 
tion and re-action lakes place among the in- 
gredients, and between them and the iron 
surfaces, which at last causes the whole to 
.unite as one mass. In fact, after a . time, the 
mixture and the surfaces of the tlanches be- 
.come a species of pyrites (holding a very 
large proportion of iron), all the parts of 
w hich cohere strongly together. 
Blood cement . — A cement often used by 
'Coppersmiths to lay over the rivets and 
edges of the sheets of copper in large boilers, 
•to serve. as an additional security to the join- 
ings, and to secure cocks, Ac. from leaking, 
is made by mixing pounded quicklime with 
.'Ox’s blood. It must be applied fresh made, 
as it soon gets hard. If the properties of this 
cement were duly investigated, it would pro- 
bably be found useful for many purposes to 
which it has never yet been applied. It is 
extremely cheap, and very durable. 
Flo nr paste . — Flour paste for cementing, 
.is formed principally of wheaten flour; boiled 
in water till it is of a glutinous or viscid consist- 
ence. It may be prepared of these ingre- 
dients, simply for common purposes ; but 
when it is used by bookbinders, or lor pa- 
per-hangings, it is usual to mix with the flour 
a fifth or sixth of its weight of powdered re- 
sin or alum; and where it is wanted still 
more tenacious, gum arabic, or any kind of 
size, may be added. 
Japanese cement, or rice glue . — This ele- 
gant cement is made by mixing rice-flour 
intimately with cold water, and then gently 
boiling it. It is beautifully white, and dries 
almost transparent. Papers pasted together 
by means ot this cement will sooner separate 
in their own substance than at the joining, 
which makes it useful in the preparation of 
curious paper articles, as tea-trays, iadies' 
dressing-boxes, and other articles that require 
layers of paper to be cemented together. 
CENCHRUS, in botany, a genus of the 
polygamia monoecia class of plants. There 
are two flowers, the one male, the other her- 
maphrodite ; the proper tlower is single, with 
two lanceolated, acuminated, concave valves: 
there is no pericarpium, and but one round- 
ish seed. There are eleven species. 
CENSOR, in Roman antiquity, a magi- 
strate whose business it was to reform the 
manners and to value the estates of the 
people. 
CENSUS, in Roman antiquity, an authen- 
tic declaration made before the censors, by 
the several subjects of the empire, of their 
respective names and places of abode. This 
declaration was registered by the censors, 
and contained an enumeration in writing of 
all the estates, lands, and inheritances, they 
possessed ; their quantity, quality, place, 
wives, children, domestics, tenants, slaves. 
CENT, in commerce, an abridgment of 
centum, is used to express the prolit or loss 
arising from the sale of any commodity: thus 
we say, there is 10 per cent, profit, or 10 per 
cent, loss; which is fog. profit, or X loss, 
upon the sale of the whole. In the trade ot 
money, it signifies the benefit or interest of 
any sum of money. Thus money is worth 
4 or 5 per cent, upon exchange. But in 
brokerage, it must be observed, that cent, is 
applied in a different manner. For example, 
if a broker or exchange-agent takes A per 
cent, for the contracts made by his interposi- 
tion, it is to be understood that there is paid 
to him A of a pound, viz. 2s. 6d. for every 
100/. he negotiated. 
CENTAUR, centaurus, in astronomy, a 
constellation of the southern hemisphere com- 
monly joined with the wolf, and called cen- 
taurus cum lupo. In Ptolemy’s catalogue, 
it .consists of 37 stars ; in Tycho’s ot 4; and 
of 35 in the Britannic catalogue, with Sharp’s 
appendix. • 
CENTAUREA, a genus of the polygamia 
frustranea order, in the syngenesia class of 
plants, and in the natural method ranking 
under the 49th order, composite. The re- 
ceptacle is bristly, the pappus simple, the 
corollulie of the radius funnel-shaped, longer 
than those of the disk, and irregular. There 
are 77 species, of which we shall only men- 
tion two, viz. 
1. Centaurea cyanus, the bluebottle, grows 
commonly among corn. The expressed juice 
of this flower stains linen of a beautiful blue 
colour, but it is not permanent. Mr. Boyle 
says, that the juice of the inner petals, with 
a little alum, makes a beautiful permanent 
colour, equal to ultramarine. 
2. Centaurea glastifolia. The root of this 
species is an article in the materia medica. 
It has a rough, somewhat acrid taste, and 
abounds with a red viscid juice. Its rough 
taste had gained it some esteem as an astrin- 
gent; its acrimony as an aperient; and its 
glutinous quality as a vulnerary: but the 
present practice takes very iittle notice of it. 
CENTER* of a bastion, a point in the 
middle of the gorge of a bastion, whence the 
capital line commences, and is generally at 
the angle of the inner polygon. 
Center of a conic section, a point in 
which the diameters intersect each other. In 
the ellipsis, this point is within the figure, 
and in tire hyperbola, without. 
Center of a curve of the higher kind, the 
point where two diameters concur. When 
all the diameters concur in the same point, 
sir Isaac Newton calls it the general center. 
Center of a dial, that point where the 
axis of the world intersects the plane of the 
dial ; and therefore in dials that have centers, 
it is-that point wherein all the hour-lines meet. 
All dials have centers, except such as have 
their planes parallel to the axis of the world. 
Center of gravity, in mechanics, that 
point about which ail the parts of a body, 
in any situation, balance each other. Hence, 
1. If a body is suspended by this point as the 
center of motion, it will remain at rest in any 
position indifferently. 2. If a body is sus- 
pended in any other point, it can rest only- 
in two positions, viz. when the center of gra- 
vity is exactly above or below the point of 
suspension. 3. When the center of gravity 
is supported, the whole body is kept from 
falling. 4. Because this point has a constant 
endeavour to descend to the center of the 
earth, therefore, 5. When the point is at li- 
berty to descend,- the whole body must also 
descend, either by sliding, rolling, or tum- 
bling down. 6. 'The center of gravity in re- 
gular uniform and homogeneal bodies, as 
■squares, circles, Ac. is the middle point in a 
line connecting any two opposite points or 
angles. Wherefore, if such a line is bisected, 
the point of section will be the center of .gra- 
vity. See Mechanics. 
Center of oscillation, that point in a 
pendulum in which, if the weight of the 
several parts was collected, each vibration 
would be performed in the same time as 
when those weights are separate. This is 
the point whence the length of a pendulum 
is measured, which, in our latitude, in a pen- 
dulum that swings seconds, is 39 inches and 
2--10ths. 'The center of suspension is the 
point on which the pendulum hangs. 
Center of percussion, in amoving body 1- , 
that point wherein the percutient force is 
greatest, or that point with which if the body : 
strikes against any obstacle, no shock shall 
be felt in the point of suspension. See Me- 
chanics. 
CENTIPES, in zoology, see Scolopen- , 
DR A. 
CENTNER, among metallurgists and as- 
sayers, denotes a weight divisible first into a 
hundred, and afterwards into other lesser 
parts. It is, however, to be observed, that 
the centner of metallurgists is the same, with 
the common hundredweight ; whereas that 
of assayers is no more than one dram, to 
which the other parts are proportional, and 
nevertheless pass by the names 100 ib. 641b. 
32 lb. Ac. 
CENTRAL forces, the powers which 
cause a moving body to tend towards, or re- 
cede from, the center of motion. See Me- 
chanics. 
CENTRIFUGAL force, that force by 
which all bodies that move round any other 
body, in a curve, endeavour to fiy off from the 
axis' of their motion in a tangent to the peri- 
