MOVJNG FORCE. 
Cases of iJjffi- through equal spaces in equal times, it can make no difference !< 
docuiilef'of whether the iime or the space be taken as an element of the i|{ 
moving force, mechanical power j and when, in such cases, Mr. Smeaton 
takes either of these, it does not follow that be abandons the ||j 
other. j 
He does not say that the consideration of the time is neces- n 
sarily excluded ; he only says it is not necessarily included in J 
the estimation of mechanical power ; and be has, at the con- )i 
elusion of the passage referred to by the reviewers, taken care | 
to discriminate the particular cases in which the time mayor | 
may not be so taken into consideration. He says, “ but no/e I 
i 
all this, (relating to the quantity of power expended in raising i 
a known weight with an uniform velocity to a known height) I 
as to be understood in the case of slow or equable motions of 
the body raised ; for, in quick, accelerated, or retarded mo- 
tion, the vis inertia of the body moved will make a varia- 
tion*.” 
He might, indeed, consistently with his principles, have ex- | 
eluded altogether the consideration of the time in which any I 
mechanical effect is produced. For, according to these prin- 
ciples, the same quantity of mechanical power is required to I 
raise a given weight to a given height, in whatever time it may | 
be effected, or whether the motion be equable or not, provided | 
that the velocity of ike tveioju at the leginning and the end of I 
the operation le the same\. Accordingly he says, “ from the I 
whole of what has been investigated, it therefore appears, that H 
time, properly speaking, has nothing to do with the production i 
of mechanical effects, otherwise than as, by equally flowing, it 
becomes a common measure j so that whatever mechanical 
effect is found to be produced in a given time, the uniform i 
continuance of the same mechanical power will, in a double 
time, produce two such effects, or twice that effect. A meeba- I 
* Pliil. Trans. 1*59, p. 106 . j 
t It is, I prc.<ufn«>, hardly necessary to say, that when the motion of |* 
the weight is so quick as to make the resistance of the air er any otlier f 
medium through which it moves, considerable ; otlier effects, beside* i 
the mere raising of tlie weight, must be taken into tlic account. 
nical il 
