Remarks on Mr. Quinby’s Crank Problem. 341 
of the exterior circle; the exterior circle representing the 
sweep of the crank. 
By the — arc AD: CD::CD: CG. There- 
fore2AD: CD::2 CD:CG. But 2 AD=are ADB, 
and 2 CD=AB. Consequently are ADB: CD:: AB 
G. Hence are ADBx CG =CDx AB. But it appears 
from a part of Mr. Quinby’s reasoning, the trath of which is 
admitted by his opponent, that when CD represents the 
whole degree of force exerted by the shackle bar on the 
crank, or, which is the same thing, (the shackle bar being 
perpendicular) the whole degree of force, exerted by the steam 
resents the mean tendency to ro- 
tation in the crank — that force preduces. Also it is evi- 
—< that in producing a semi-rotation of the crank, the pis- 
ton moyes through a ear equal to AB; and during the 
same time, the crank moves through the semi-cirtile ADB. 
But it has been shown that ADB x CG=CD x AB. There- 
fore the distance passed through by the piston, multiplied by 
the force by which itis driven, is equal to the distance through 
which the crank moves, multiplied by the mean force by 
which it is driven ; or in other words, the power and ‘econ 
are equal in quanti 
We might show with equal clearness, that the quantity of 
power exerted onthe piston, and of direct effect on the crank, 
are equal in any of the parts of their respective motions, which 
are simultaneously performed ; and also that no difference 
tain in this result, if, instead of remaining perpen- 
as I intend, before I close, to give a general course of reason 
i i whic h ill embrace a et : i a 
the piston and the offi, by the use of the phat we naae 
not shown, nor has Mr. Quinby, that there is none between 
the piston and the boiler, resulting from a proxi- 
mate cause. Mr. Quinby, therefore, had the logic of bis ar- 
gument been pure, could not have drawn from it the infer- 
ences which he does, viz. that there is no loss of power sus- 
tained by the use of the crank, and that the attempts to con- 
struct a rotary engine are idle. fore he could do this, he 
should show that steam, under like circumstances in other res- 
pects, will exert the same quantity of power, in proportion 
to the quantity of steam expended, on a piston which meets 
