MKKrriJY STAN|).MU)S OF RESISTANCE, KTC. 



H7 



in :i ilniililc t;ink designed for the measurement of standards t' n-sistance. This tank 

 is shown in fig. 10 with the coils in position. M is a small eleotro-lBOiOf employed 



Fig. 10. 



to drive the vane V. The stirring arrangements and communicating tubes are such 

 that oil is pumped from the lower part of the tank T to the top of T', and afterwards 

 circulates from the bottom of T' to the top of T. The whole apparatus is set up in a 

 constant-temperature room, no difficulty being experienced in keeping the bath steady 

 to 0-1 C. 



The shunting of one of the coils Q, R, or S is effected by the turning head shown, 

 the appropriate connections with the resistance box r being thus immediately made. 



P' is a standard m;tnganin coil belonging to the British Association, and was used 

 extensively throughout the comparisons. It is Wolff coil No. 1690, having a small 

 temperature coefficient (+ O'OOl per cent, per rise in temperature of 1 C. for an 

 average temperature of 17 '" < '. I. .m<l is knOWD tfl tan raBMned OOOStUll in \.ihn- 

 for several years. The value of 1690 has been obtained by means of a long series of 

 observations with the platinum silver coils of the British Association. The unit in 



