57G 
MR. W. C. D. WHETHAM OX THE ALLEGED SLIPPIXG 
each observation the drop of water was removed by blotting paper. At any given 
temperature the apparatus was therefore in a definite state, and this was obtained at 
much less expenditure of time and patience than if the bulb had been always filled 
to a certain mark at a certain temperature, or the same mass of water always put in 
by adjusting the weight. A mirror was attached to the bulb by sealing wax, and the 
whole suspended bifilarly by a fine copper wire. The logarithmic decrement had to be 
reduced by suspending two brass balls at the end of a long bar magnet which was 
fixed to the bulb and by means of which the apparatus was set in oscillation. 
A series of preliminary observations gave as the ratio of the frictions 1 : I'OOOl, an 
accuracy in the proof of identity which was not justified by the roughness of the 
observations, but which, at any rate, showed that the difference could not be very great. 
After a week spent in preliminary investigation, the apparatus w'as set up in the 
