On a New Form of Ergometer. 87 



Let a,— number of beats of pendulum (1) per period = — ; 



• . c i 



Let a 2 = number of beats of pendulum (2) per period =—; 

 Cj and c 2 being small fractions less than e 2 . 



Let Nx = whole number nearest to w x ; 

 Let N 2 = whole number nearest to n 2 . 



Tnen w 1 + cr 1 =N' 1 . 



n 2 + c 2 = N 2 - 



n 1 —n 2 + Ci — c 2 = Ni— 2ST a = M, a whole number. 



n\—n 2 -\-c x — c 2 is less than 2(« 1 + g 2 ). 



If, therefore, 2(0 1 -t-* 2 ) is numerically less than §, then M=0, 



whence N 1 =N' a = K 





n l — N — C\ _ 



Jl andN= Cl ' 2 ~ 



-Ca$i 







n 2 N — c 2 



t 2 t 2 - 



-k 





Eight determinations of the rate of an Ut 2 fork, 



made by the 



preceding 



method, gave the following results :— 





Temp. Fahr. 



V. s. 



v. s. at 60° F. 



Diff. from mean. 



54-0 



128*134 



128-090 





+ 0-003 



56-3 



128-114 



128-087 





o-ooo 



58-0 



128-102 



128-087 





o-ooo 



60-0 



128-090 



128-090 





+ 0-003 



62-2 



128-077 



128-093 





+ 0-006 



63-0 



128-060 



128-082 





-0-005 



64-5 



128-050 



128-083 





-0-004 



73-5 



127-984 



128-084 





-0-003 



XY. On a New Form of Ergometer* . 

 By Feederick John Smith, B.A.f 



IN the present period of electrical science, in addition to 

 that branch which deals with lighting, another very im- 

 portant branch has grown out of the great stock, viz. the 

 distribution of power, as the different Companies call it. 



In estimating the qualities of various electromotors, and 

 also in certain physical experiments connected with motion 

 (for instance, to illustrate the amount of work done to keep 

 the balls of a centrifugal governor at any given angle), some 

 sort of very sensitive ergometer is required. In dealing with 

 a few foot-pounds per minute instead of many horse-power, 

 great care must be taken that the ergometer be of consider- 

 able range, dead-beat in its action, and that it have no internal 



* The term " Ergometer " is now logically used for Dynamometer. See 

 Thomson and Tait's ' Elements of Natural Philosophy.' 

 t Communicated by the Author. 



