Electromagnetic Stress. 



259 



The two halves of the ellipsoid were soldered into tubes 

 which could be fitted tightly, axially, into the coils, the free 

 ends projecting by amounts regulated by nuts, N (fig. 1), 



1. — Longitudinal vertical section of Traction Apparatus. 



Fit 



running on the tubes. To secure good alignment of the half- 

 ellipsoids, a small brass ring, B, of 1 millim. width, was made 

 to fit tightly on one half and loosely on the other at the 

 plane of contact. This ring was afterwards found to be an 

 important part of the apparatus, results obtained without it 

 being very uncertain. 



To the absence of such a guide in Bosanquet's experiments 

 may probably be attributed, to some extent, the uncertainty 

 of his results, especially at high inductions. 



One coil was suspended from a tripod stand by two rods 

 provided with nuts and screws, by which and two other screws 

 (not shown in the diagram) the coil could be raised or lowered, 

 levelled, and rigidly fixed. Below this was a platform, P, with 



