32 



Mr. J. H. Pointing on a method of 

 Determination of (B + Y) — ( A + X) . 



[Nov. -.21, 



Weight in 

 pan. 



B + Y 



A + X 



B + Y 



Extremities of 

 oscillations. 



208-5 

 221-7 



209 -5 



246-9 



214 -4 

 244-1 



219 -2 



215-6 

 218 -0 



Resting point. 



515 -35 



229-95 



217 -1 



Mean of pre- 

 ceding and 

 succeeding 



resting points 



216-32 



230 -91 



Differences. 



13-73 



13-81 



A + X 



240-8 



221 -0 

 238-7 



231 -87 



217-12 



14-75 



B + Y 



226-1 



209-4 

 223-7 



217 -15 



232 -24 



15 -09 



A + X 



B + Y 



221 -8 



242-3 

 224-1 



211 -5 

 221 

 212-0 



232 62 



216 -77 



216-96 



232 -21 



15-66 



15 -44 



A + X 



219-0 



243-0 

 222-2 



231-80 



B + Y 



208 -3 



229-0 

 209-9 



219 '05 



This sudden change of resting 

 point must be due to some 

 irregular disturbance. It 

 is therefore rejected. It 

 was slowly returning to 

 nearly its former values. 



Mean (B + X) — (A + Y)=1475 divisions ='12831 milligramme. 

 Greatest deviation from the mean =1*02 division =-0089 mgm. 



The great difference between the resnlt here and that in series Y is 

 probably due to deposit of dust. The new mirrors had to be fixed up 

 just before the experiment began, and the doors were open for some 

 time. At the conclusion of the weighing I found a good deal of dust 

 on the weights. 



