[ 531 ] 



LX. On Electromagnets. — No. I. 

 By B. H. M. Bosanquet, St. John's College, Oxford. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



THIS paper contains the results of the complete examina- 

 tion of two cylindrical electromagnets, with so much 

 comment as is needed to show r the nature of the generaliza- 

 tion which is being worked out. 



In the following tables of results, each normal place re- 

 presents a number of experiments. The number of normal 

 places has been reduced as far as possible consistently with 

 exhibiting the course of the values. 

 The quantities are as follows: — 



§$, magnetic induction (number of lines of force through 

 unit area, field intensity) through equatorial section of 

 magnet ; 



p, magnetic resistance = ™gnetfc potential 



47TftC 



where n is the total number of coils, and the current 

 inC.G.S.; 



Earth's force, H, V; H='1723 in the mean, 



V='433; 

 ampere-turns = 10 nG ; 



/, focal distance in terms of length = ZxHneso ffo^ e 5 

 M, moment ; 



moment ,. ,* n 



m — = magnetization. 



; volume 



The bars are wound uniformly from end to end. If the 

 magnetizing coil be concentrated towards the middle the 

 magnetic resistance is diminished. 



The induction-coils are concentrated as close as possible to 

 the equatorial section. If they are distributed more towards 

 the ends, the apparent magnetic resistance is increased. Their 

 number was varied between 200 and 1. 



