88 



R. W. Willson — Magnetic Field 







I 









use for other investigations. With one exception this stove 

 was the only mass of iron casually present whose effect it was 

 not easy to eliminate by reversal or removal at the time of the 



observations. 



— *~ 



B 



I 



Fig. 1. Plan of west wing of the Jefferson Physical Laboratory, with Mnes of 

 equal directive force in planes 5 ft. above first floor. 

 E, elevator. 



G. point below iron stove on second floor. 

 p p p, piers. 



When by the courtesy of Prof. Trowbridge and the Director 

 of the Laboratory, Prof. Lovering, I obtained for a special re- 

 search the use of one of the rooms of the non-magnetic wing 

 (No. 17 on the plan fig. 1), it became necessary for me to in- 







