[ 27 ] 
wheel, and gives the weight liberty to deicend. But 
if the defcent be too quick, he pulls the lever a little 
farther down, fo as to make it rub againfl the round 
edge of a wheel, by which means he lets the weight 
go down as flowly as he pieafes ; and, by pulling a 
little harder, he can fop the weight, if needful, in 
any part of it’s delcent. If he accidentally quits his 
hold of the lever, the catch immediately falls, and 
fops the whole machine. 
In the figure of this crane [Tab. I.] A is the 
great wheel, and B it’s axle on which the rope C 
coils. This rope goes over a pulley D in the arm 
of the gib E, and is hooked to the' weight F for 
drawing it up. G is the winch, H the largeft trun- 
dle, I the next largeft, and K is the axis of the 
fmalleft trundle, which is fuppofed to be hid from 
view by the upright fupporter L. M is a trundle, 
which is turned by the great wheel; and on the axis 
of this trundle is fixt the ratchet wheel N, into the 
teeth of which the catch O falls. P is the lever, 
from which goes a rope QjQ^over a pulley R, to the 
catch; the end of the rope being fixed into the lever 
and catch. S is an elaflic bar of wood, of which, 
one end is fcrewed to the floor ; and from the other 
end (out of fight in the figure) goes a rope to the 
farther end of the lever, beyond the pin or axis on 
which it turns in the upright fupporter T. The ufe 
of this bar is to keep up the lever from rubbing 
againft the edge of the wheel U, and to let the catch 
keep in the teeth of the ratchet-wheel. But, when 
the end P of the lever is pulled down, it lifts the 
catch out of the ratchet wheel by means of the rope 
QCF and gives the weight F liberty to defcend : 
E 2 bi* 
