ON THE SPECIFIC HEAT OF WA'IKI; 



219 



current of 5 amperes was very small, the test could be made. Not having available 

 such a heavy standard, the comparison was made with the resistances MI, M 2 , the 

 calibration of which was described in the last section. MI having a bore of 2 mm. and 

 M a a bore of only 1 mm., the current density in M, was four times as great as in MI. 

 The constant terms were ascertained at the date of the test, and in M a all the 

 mercury in the leads above the level of the baffle plate was removed, the coefficients 

 of M a and Mj" Ixjing thus slightly altered. The values of the resistances were : 



M, = 



To Dynamo 



-0278m s +0-0001354m a 3 . 



The resistances were arranged in bridge, as shown in fig. 7, the resistance It (alxmt 

 19,000 ohms) Ijeing adjusted to obtain equilibrium with different values of current. 

 A stream of water was kept flowing around 

 the glass spirals containing the resistances, 

 but, as the current was kept on con- 

 tinuously, the temperature rose slowly, 

 and gave some trouble in getting the 

 required simultaneous scale readings. In 

 the accompanying table, the current used is placed in the first column, the next 

 two columns give the thermometer-resistance scale readings, the next two the 



TABLE III. Test of Thermometer-resistances under Various Currents. 



Experiment 147. 



Fig. 7. 



resistances calculated from the formulae by means of the readings, the next the ratio 

 M,/M 2 , the next the value of the resistance R when adjusted for equilibrium. The 

 value of R divided by 100,000 is the ratio which should be equal to M,/M a , the 



2 v 2 



