C 73 1 ] 
fame fwiftnefs of motion, when the lever is moved 
upwards, as downwards. 
The great wheel I, fixed on the arbor K, turns 
the pinion c, on the arbor of which the crank d (to 
move the ventilator), and the fly e (to help the mo- 
tion), are fixed. The pinion c y is turned three times 
by each alternate motion of the lever ; which may 
be increafed, or diminilhed, according to the numbec 
of teeth in the pinion c. 
The number of teeth in the wheel A is fixty-fix, 
but need not be toothed above half way. Inftead 
of this wheel there might be a barrel, with a chord 
round it, fixed at each end of the arch of the lever, 
and projecting fomewhat from it; which, by the 
motion of the lever, would work in the fame man- 
ner in other refpeCts, and be eafier made, and at lefs 
expence. 
The wheel D fixed to the rochet C has thirty-three 
teeth, and its pinion G eleven. 
The wheel F fixed on the arbor K has twenty- 
four teeth, and its pinion H fixteen. 
The greater the number of teeth in the rochets, 
the better. 
'Tab. 26. contains the plan (in parts) of the whole 
machine, except the lever B and fly e y which are in 
Tab. 27. 
Tab. 27. alfo contains the elevation of the arbor, 
with its different fixtures ; viz. 
Fig. 1. The rochet C and wheel D {Tab. 26.) fixed 
together. 
2. The outfide wheel F that works the pinion- 
wheel H {Tab. 26). 
5 A 2 Fig. 
