Transverse Fields and Allied Phenomena. 



417 



example of the decrement of rigidity due to a current of one 

 ampere in an iron wire suspended in air, compared with the 

 effect when the wire is submerged in flowing water, other 

 things being equal. It will be seen how relatively large the 

 heat effect is, the decrements for the submerged wire being 



less than l om at 5 meters of distance and 90° of twist lying 

 within the errors of measurement. Apart from this the ques- 

 tion is open whether even the submerged wire is not heated 

 to an extent appreciable by the method of observation. 



Hence in my concluding experiments I tested an iron and a 

 brass wire of about the same dimensions, in the same apparatus 

 and under like condition consecutively. Both were submerged 

 in running water. The results for iron are given in figure 10, 

 those for brass in figure 11. The wires were sufficiently thin 



360° -%W -"/«' 



.210. 



fea. \oJrok. 



' U i 



and the current strong enough to give large deflections (up to 

 50 om ). The current and diameter in brass (6 amp., -020 cm ) are 

 smaller, in iron (7*5 amp., -044 om ) larger. In both cases, 

 however, there is a definite decrement of rigidity due to the 

 circular field of about the same order, and in both cases so far 

 as can be made out it is a mere heat effect. 



I am obliged therefore to conclude, that in so far as these 

 experiments have weight the effect of longitudinal magnetiza- 



