Remarks on Mr. Quinby’s Crank Problem. 348 
the case necessarily ~— Thus, when we say that the pow- 
er of the steam in an engine, operates to a disadvantage om 
the crank, if the pitman be oblique to the crank, we meam 
power in degree. But when we say, that this disadvantageous 
action occasions no loss of power, we mean, power in quan- 
tity. And when we speak in general terms of the power of 
the steam engine, we use the word in a still higher sense ; @ 
sense in which it involves three attributes; and could be ex- 
pressed only by the product of three unlike quantities, viz. the 
egree of force on the piston, the length of the stroke, and 
the number of strokes per minute.* 
It also appears from = — remarks, that if we 
would compare the power exerted on a machine, with the ef- 
fect produced by it, we ieee siichies the nature of the ef- 
fect produced, and ‘the purpose for which the estimate is 
made. If the effect be that of confining a body in a fixed 
“position, itis in degree only, and the comparison can 
made only in degree. Butin machinery in which the effect 
is produced by motion, the comparison may be made either 
in degree or in quantity ; according to the perpen whic 
the estimate is made. If, in such machinery, the 
the comparison be to determine to what extent the dégive of 
power is modified, the estimate will be made in degree only. 
The lever, and other instruments, commonly called the me- 
chanical powers, are usually constructed for the purpose of 
modifying in degree, an existing power, in order to adapt it 
to the production of an effect, which is either greater or less 
in degree, than the power. In ma ing an estimate of the ef- 
fect of such machinery, therefore, our object is easels ac- 
effect in degree 
But ie mnacinery ornare constructed for i the 
ing a continued power, (as that of water or: 
steam) to the ee of aun effect, if we would compare: 
the power with the effect, in order to determine whether the 
power be profitably expended, the comparison must always 
ty. <p aE a 
If in making such a comparison as that last tientioned, we 
take for the power, that which is actaally applied to the ma- 
chine in the given case, as Mr. Quinby does in his demon- 
Mr. Quinby, in one of his communica tions to this is work, gives a “ Defi- 
nto of the oaee r “ the steam engine,”. which involves oaks the * frst of 
se three attributes. This evidently can be no test of the effect which the 
prc ‘produces, we when the other attributes are given. 
