Mr. Quitiby on- Crank Motion. 345 
one he is endeavouring “46 correct He informs us that in 
the proportions am: aS:: Ce: CS; and dn: aS:: Ce: 
Ct, the third terms are the same ; ze. Cc and Ce are the 
same!*. It is true that in ee reasoning to show that the 
principle assumed by Mr. Ward is not correct, I did com- 
mit an error ; and this I now sleet fully acknowledge, notwith- 
standing the writer of this ‘‘ Examination” has failed to prove 
it. My error was in assuming four lines proportional, which 
are not oe This oversight was a out to me 
last winter by my scientific friend Prof. R. atterson 3 
and it was my determination to forward a correction for the 
ensuing number of this Journal. The day after Prof. P- 
pointed out to me the error, I shewed him the following 
correction. 
Let the fig. represent the crank, and sd 
be a tangent to the circle: it is required 
to prove that “ the effects of the power 
to produce rotation at the several points 
of division of the quadrant, are notas the 
rpendiculars reper from those 
points to the line of force.” 
For the effect of P at the point a, we have 
Px hata E =Px CaP x Ca; 
Sm Ce 
and for the effect of P at the point d, we 
Sd Ci 
have PxXe x Cd=P x Gi * Cd =P 
xCt. And Mw if the principle as- 
_ sumed ard were fue, then 
would am ue dn:: Cv: Ct; or am: Cov: : 
i. Ct bat this we can readily perceive is not te ease ; 
for if @ be supposed to move forward till it be at the point 
D, itis plain that am will be =Cv ; but dn is not =r s 
therefore the principle assumed by Mr. Ward is not correct ; 
pe my proposition, eS the f this ‘‘ Examination” 
sserts is incorrect, is tru 
= shall now offer a few saicaekl on the demonstration which 
of this “ Examination” has given of the Crank 
pos He finds the equa tion @R=Px, andfrom athe delice the 
* iets ponsibli Ube the weiter oT Mile Eanes thet case & the terms 
VOL. XI—NO. a 
