[ 26 ] . 
the largeft trundle did; becaufe it makes twice as 
many revolutions for one revolution of the wheel and 
it’s axle : and then the power gained will be as fix- 
teen to one, becaufe the velocity of the power will 
be fixteen times as great as the velocity of the weight. 
If the weight be too great for this power to raife 
(which we ftill fuppofe to be exerted by one man) the 
winch may be put upon the axis of the third (or 
fmalleft) trundle, and then, in turning the winch, 
the power gained will be as thirty-two to one. 
But if the weight fhould be too great, even for this 
power to raife, the power may be doubled by draw- 
ing up the weight by a double rope, going under a 
pulley in the moveable block which is hooked to the 
weight, below the arm of the gib ; for then, the 
power will be as fixty-four to one. If the block has 
two pullies, and the rope be twice doubled below 
them, the power will be as 128 to one: and fo on, 
by adding more pullies, according to any required 
proportion. 
Whilft the weight is drawing up, the racch-teeth 
of a wheel Hip round below a catch or click that falls 
fucceffively into them ; and fo hinders the crane from 
turning backward, and detains the weight in any part 
of it’s afcent, if the worker fhould happen acciden- 
tally to quit his hold of the winch ; or choofe to reft 
himfelf before the weight is quite drawn up. The 
catch, in this crane, is conftrudted much in the fame 
way as in the great crane at Briftol, invented by the 
late Mr. Padmore, of that city. 
In order to let down a weight, the man who works 
the crane pulls down one end of a lever of the fe- 
cona kind, which lifts the catch out of the ratchet- 
wheel, 
