598 



Prof. C. Bams on the 



of inertia, k, of the watch without ballast is easily found from 

 its mass (65"874). In this way, roughly, Z.- = 681 g.cm. 2 

 The increments of moment of inertia, 8k, were directly com- 

 puted. They were produced by successively increasing small 

 metallic masses, all added at a distance of about 6 cm. below 

 the knife-edge. 



The table, which is an example of a single series of observa- 

 tions, is otherwise clear. The rates are given in seconds per 

 hour of the chrouometer (time in hours and fractions of an 

 hour) for each pair of consecutive observations, since this 

 method lends itself well for description in the annexed chart, 

 where curve I. shows the advance of the watch (ordinate) in 

 terms of the chronometer time (absciss;)). The given series 

 applies for an added ballast, increasing the inertia k about 

 3 per cent. The rates are inscribed on the successive 

 branches of the curve. It will be seen that two typical rates, 

 respectively positive and negative, are involved. 



Table I. — Time and successive rates of the rocking watch. 

 £ = 681 g.cm. 2 Ballast added b* cm. below knife-edge. 





Chrono- 



Advance 



Successive 



Average 



Average 



Ballast. 



meter 



of watch 



rates 



rate : long 



rate: short 





(hours). 



(sec). 



(sec. /hour). 



period. 



period. 



(^'=20 g.cm. 2 



1034 



- 13 





-46-0 s./h. 



+ 16-1 s./h. 





17-78 



+ 170 



+ 16 







cW£-03 



33-83 



+ 373 



+ 16 









41-07 



- 45 



-58 









57-35 



- 821 



-48 









65-88 



- 672 



+ 17 









81-75 



- 443 



+ 14 





- 





90-28 



- £8:s 



+ 18 









105 72 



- 49 



+ 15 









114-82 



+ 108 



+ 17 









129-32 



+ 322 



+ 15 









13810 



- 86 



—46 









153 53 



- 795 



-46 









162-33 



- 636 



+ 18 









177-27 



- 415 



+ 15 









186-30 



- 772 



-39 









201-40 



-1378 



-40 









209-62 



-1236 



+ 17 









225-58 



- 996 



+ 15 







The rates obtained in all the different series for successive 

 increments of the moment of inertia are given in Table IT. 

 and in the corresponding chart, fig. 2. For convenience in 

 plotting, the successive observations are supposed to have 



