376 



MESSES. V. H. VELEY AND J. J. MANLET ON 



thrown into one arm of the bridge, while the coil and its leads are in another arm 

 thus, changes in resistance of the leads produce no effect on the readings. The 

 values for R in steam and ice were ascertained by different arrangements of plugs, 

 and hence different bridge wire readings. The coils used are indicated by letters. 



STEAM. 



The boiling point of water for -p = 748*78 is 99*59 ; hence the value for R under 

 this condition is 19T355. 



ICE. 



Hence II = 172-288, if t = ; similarly, for t = 20'15 R was found in the same 

 manner to be 176-149. Taking R at as 1, R at 20'15 = 1*02241, and at 

 99-59 = 1-11067, the curvature is very slight, and is expressible by the equation 



R,= l + -0011123 t; 

 but if R 15 := 1, then R = -0010911, and the equation for the temperature coefficient is 



SB, = R 15 (l + (t- 15) X -001094), 

 with a probable error of 1 in 1000. 



CONSTRUCTION OF THE BRIDGE. 



In preliminary experiments with the ordinary form of metre bridge used with a 

 telephone and small induction coil as described by KOHLRAUSCH and others, difficulty 



