CEN 
CEN 
sure of the atmosphere. This macliine con- 
sists of a large tube of copper, &c. in the 
form of a cross, placed perpendicularly in 
the water, and resting at the bottom on a 
pivot. At the upper part of the tube is an 
horizontal cog-wheel, w'hich touches the 
cogs of another in a vertical position ; so 
that by the aid of a double winch, the 
whole machine is moved round with very 
great velocity^ Near the bottom of the 
perpendicular’ part of the tube is a valve 
opening upwards ; and near the two extre- 
mities, but on the contrary sides of the 
arms, or cross part of the tube, are two 
other valves opening outwards. These two 
valves are kept shut, by means of spr ings, 
till the machine is put in motion ; when the 
centrifugal velocity of the water forces 
them open, and discharges itself into a cis- 
tern or reservoir placed there for that pur- 
pose. On the upper part of the arm are 
two holes, which are closed by pieces that 
screw into the metal of the tube. Before 
the machine can work, these holes must be 
opened, and water poured in tlirough them, 
till the whole tube be full ; by these means 
all the air will be forced out of the ma- 
chine, and the water supported in the tube 
by means of the valve at the bottom. The 
tube being thus filled with water’, and the 
holes closed by their screw-caps, it is turn- 
ed round by the winch ; when the water in 
the arms of the tube acquires a centrifugal 
force, opens the valves near the extremi- 
ties of the arms, and flies out with a velo- 
city nearly equal to that of the extremities 
of the said arms. 
If tire men who w’ork the machine be 
supposed to turn the winch round in tliree 
seconds , the machine will move rotrnd its 
axis in one second ; and, conseqirently, each 
extremity of the arms will move with a ve- 
locity of 18.8 feet in a second. A column 
of water, tlierefore, of three inches dia- 
meter, will issue through each of the valves 
with a velocity of 18.8 feet in a second ; 
but the area of the aperture of each of the 
valves is 7.14 inches ; which, being multi- 
plied by the velocity in inches = 125.6, 
gives 1610.784 cubic inches, the quantity 
of water discharged through one of the 
apertures in one second ; so that the whole 
quantity discharged in that space of time 
through both the apertures is = 3221.668 
inches ; or 193294.08 cubic inches in one 
minute. But 60812 cubic inches make a 
tun, beer-measure ; consequently, if we 
suppose the centrifugal piachine to revolve 
ironnd its axis in one second, it will raise 
nearly 3 tuns 44 gallons in one minute ; but 
this velocity is too great, at least to be 
maintained for any considerable time : so 
that, w^hen this and other deficiencies in 
the machine are allowed for, two tuns are 
nearly the quantity that can be raised by 
it in one minute. As tlie water is forced 
up the perpendicular tube by the pressure 
of the atmosphere, it is evident that this 
machine cannot raise water above 32 feet 
high. 
CENTRIPETAL /orce, that force by 
which a body is every where impelled, or 
any how tends towards some point as a cen- 
ter ; such is gravity, or that force whereby 
bodies tend towards the center of the earth ; 
magnetical attraction, whereby the load- 
stone draws iron ; and tliat force, whatever 
it be, whereby the planets are continually 
drawn back from right-lined motions, and 
made, to move in curves. 
The greater the quantity of matter in any 
body is, the greater will be its centripetal 
force, all things else alike. If a body laid 
upon a plane revolve at the same time, and 
about the same center with that plane, and 
so describe a circle ; and if the centripetal 
force, wherewith the body is drawn every 
moment towards the center, should cease 
to act, and the plane .should continue to 
move with the same velocity, the body will 
begin to recede fi om the center about which 
the plane moved. See Central /orces. 
CENTRISCUS, in natural Listoi’y, a 
genus of fishes, ranked among the branchi- 
ostegous order of Linnaeus, but by Dr. Shaw 
among the Cartilagenei. Generic character ; 
snout lengthened; body compressed, cari- 
nated beneath ; ventral fins united. There 
are but three species; viz. the scutatiis, 
scolopax, and the velitaris. All are found 
in the Indian seas, and tlie scolopax is like- 
wise a native of the Mediterranean. 
CENTROGASTER, in natural history, 
a genus of fishes of the order Thoracic!. 
Generic character : head compressed, 
smooth; gill-membraned, mostly seven 
rayed ; body depressed, smooth ; fins spi- 
nous j ventral connected by a membrane, 
with four sharp spines, and six soft rays. 
There are four species. 
CENTUNCULUS, in botany, a genus 
of the Tetrandria Monogynia class and or- 
der. Natural order of Rotacese. Lysima- 
chiae, Jussieu. Essential character : calyx 
four-cleft ; corol four-cleft, spreading ; sta- 
mina short ; capsules one-celled, opening 
horizontally. There is but one species, viz. 
C. minimus, bastard pimpernel, is an an- 
