324 PROFESSOR WHEWELL, ON CAUSE AND EFFECT. 



of alteration. The steady rate is the indication of the absence of any cause 

 of alteration ; and the rate of going measures the progress of time, in a 

 state of things in which causes of change are thus excluded. If an altera- 

 tion takes place in any part of the clock, once for all, the rate is altered ; 

 but the new rate is steady as the old rate was, and, like it, measures the 

 uniform progress of time. But the difference between the new rate 

 and the old is occasioned by the difference of the parts of the clock ; and 

 the new rate may very properly be said to be caused by the change of 

 the parts, and to be subsequent to it : for it does prevail after the change, 

 and does not prevail before. 



But how is this view to be reconciled with the one just quoted from 

 the Reviewer, and, as it appeared, satisfactorily proved by him ; accord- 

 ing to which all mechanical effects are simultaneous with their causes, 

 and not subsequent to them? We have here the two views in close 

 contact, and in seeming opposition. 



In the going of a clock, the parts are in motion ; and these motions 

 are determined by forces arising from the form and connexion of the 

 parts of the mechanism. Each of the forces thus exerted at any instant 

 produces its effect at the same instant ; and thus, so far as the term cause 

 refers to such instantaneous forces, the cause and the effect are simul- 

 taneous. But if such instantaneous forces act at successive intervals of 

 time, the motion during each interval is unaltered, and by its uniform 

 progress measures the progress of time. And thus the motion of the 

 machine consists of a series of intervals, during each of which the motion 

 is uniform, and measures the time; separated from each other by a series 

 of changes, at each of which the change measures the instantaneous 

 force, and is simultaneous with it. And if, in this case, we suppose, at any 

 point of time, the instantaneous forces to cease, the succession of them 

 being terminated, from that point of time the motion would be uniform. 

 And since the rate of the motion in each interval of time is determined 

 by the instantaneous force which last acted and by the preceding motion, 

 the rate of the motion in each interval of time is determined by all the 

 preceding instantaneous forces. Hence, when the series of instantaneous 

 forces stops, the rate at which the motion goes on permanently, from that 



