C 2 5 ] 
Three trundles, with different numbers of daves, 
are applied to the cogs of a horizontal wheel with an 
upright axle ; and the rope, which draws up the goods, 
coils round the axle. The wheel has 96 cogs, the 
larged; trundle 24 daves, the next larged 12, and 
the finalled has 6. So that the larged trundle makes 
4 revolutions for one revolution of the wheel and 
it’s axle, the next larged makes 8, and the fmalled 
makes 16. A winch is occafionaliy put upon the 
axis of either of thefe trundles for turning it- the 
trundle being ufed that gives a power bed fuited to 
the weight : and the handle of the winch defcribes a 
circle, in every revolution, equal to twice the circum- 
ference of the axle of the wheel. So that the 
length of the winch doubles the power gained by 
the revolutions of each trundle. 
As the advantage gained by any machine or engine 
whatever, is in dired proportion of the velocity of 
the power to the velocity of the weight , the powers 
of this crane are eafiiy edimated; and are as fol- 
lows. 
If the larged trundle be turned by the winch, it 
will make four revolutions for one revolution of the 
great axle on which the rope coils in drawing up the 
weight and as the length of the winch is double 
the femidiameter of the axle, the power gained will 
be as eight to one : that is, a man will be able to raife 
eight times as much weight by means of the engine, 
as he could do by his natural drength without itT al- 
lowance being made for fridion. 
i If the weight be too great for this power to raife, 
the. fecond trundle may be turned by the winch, 
which will turn the wheel and axle twice as flow as 
Vol. LIV. E the 
