OF NATURAL PHILOSOPHY. 127 



the preference as an original measure to the former, 

 because any error committed in the process by 

 which that is determined becomes subdivided in 

 the final result ; while, on the other hand, any mi- 

 nute error committed in determining the length of 

 the pendulum becomes multiplied by the repetition 

 of the unit in all measurements of considerable 

 lengths performed in yards. 



(121.) The same admirable invention of the pen- 

 dulum affords a means of subdividing time to an 

 almost unlimited nicety. A clock is nothing more 

 than a piece of mechanism for counting the oscil- 

 lations of a pendulum ; and by that peculiar property 

 of the pendulum, that one vibration commences 

 exactly where the last terminates, no part of time is 

 lost or gained in the juxta-position of the units so 

 counted, so that the precise fractional part of a day 

 can be ascertained which each such unit measures. 



(122.) It is owing to this peculiar property by 

 which the Juxta-position of units of time and weight 

 can be performed without error, that the whole of 

 the accuracy with which time and weight can be 

 multiplied and subdivided is owing. * The same 

 thing cannot be accomplished in space, by any method 



* The abstract principle of repetition in matters of measure- 

 ment (viz. juxta-position of units without error) is applic&blc 

 to a great variety of cases in which quantities are required to be 

 determined to minute nicety. In chemistry, in determining 

 the standard atomic weights of bodies, it seems easily and com- 

 pletely applicable, by a process which will suggest itself at once 

 to every chemist, and seems the only thing wanting to place 

 the exactness of chemical determinations on a par with astro- 

 nomical measurements. 



