HALL AND CAMPBELL. — MAGNETIC EFFECTS IN SOFT IRON. 037 



Ettiiii^sluiusen effect in Plate 2, and the results here attained are not 

 entitled to any great confidence. They are 



It seems inadvisable to calculate a temperature-coefficient of ^7), 

 from these data,. 



With Plate 2 we put the circuit C^Ki into connection with the 

 west coil of the galvanometer and the circuit C«K<i into connection 

 with the east coil, as in Figure 9.^ We shall call this arrangement 

 C'iKi vs. C2K2, or (4) vs. (2). Series with this arrangement were 

 coupled with series having a (2) vs. (4) arrangement, the galvanometer 

 connections being exchanged in the shift from one arrangement to the 

 other. The results are 



The numbers given in brackets, which are the ones to be finally 

 taken, are reached by deducting 1.5 per cent from the numbers immedi- 

 ately above, the deduction being made for reasons given in connection 

 with eTe- 



From these data we get the following temperature-coefficient of eT^ 

 in Plate 2 : 



(612 — 492) -f- 492 (83.9 — 12.2) = 0.0034. 



The transverse differences of temperature (between the arms) actu- 

 ally produced by electromagnetic action in the cases here described in 

 Plate 2 were about 0.0053° at the low temperature and 0.0067° at the 

 high temperature. Whether these temperature-differences are set up 

 instantaneously by the magnetic action or whether they grow for a 

 time after the full magnetic field-strength is on, is a question we can- 

 not at present answer with full confidence. The galvanometer was 

 usually read about 45 to 60 seconds after the magnet-current, C„, was 

 put on. We have not observed any tendency toward galvanometer 



^ Proportions are not observed in this figure, nor is the device for keeping 

 the two wires separate, except at their soldered junction, within the glass 

 tubes in V shown. For this detail see Figure 10. 



