HALL AND CAMPBELL. — MAGNETIC EFFECTS IN SOFT IRON. G31 



Mounting the Plates in 

 THE Field. 



Figures 7 and 8 show the 

 method of mounting the plates 

 in the magnetic field for the 

 electromagnetic experiments. 

 7" 7' is a trough of soft iron 

 consisting of a rectangular 

 one-piece^ block about 4.5 

 cm. long, 6.5 cm. tall and 

 2.0 cm. wide, with a channel 

 0.5 cm. wide and 5.5 cm. deep 

 cut through it from end to 

 end, leaving an uncut part 1 

 cm. thick below. Through 

 holes drilled in this uncut 

 portion two streams of water, 

 entering at the ends and 

 meeting at the middle, reach 

 ten vertical passages, five in 

 each wall of the trough. The 

 passages in each wall lead 

 into a horizontal passage at 

 the top, and the two streams 

 of water issuing from the 

 apparatus are reunited into 

 one beyond the range of our 

 figures. 



The object of this water 

 circulation is to control the 

 temperature of the trough, and 

 so that of our iron plate, which 

 lies in the channel of the 



^ The trough first used was not 

 from one piece, but was a com- 

 posite affair soldered together. 

 It leaked more or less, and after 

 much trial the new trough was 



substituted for it March 26, 1910. Nearly all our observations on the 

 transverse and longitudinal effects made before that date we regard as tenta- 

 tive only and reject from our final results. 



