Magnetic Permeability of Liquid Oxygen and Liquid Air. 285 



a little separated, thus forming apertures by which liquid could enter 

 or leave the annular inner core. 



The nature of this transformer is shown in Fig. 1. 



FIG. 1. 



Diagram of the Closed Circuit Transformer used in the Experiments. 



The mean perimeter of this rectangular-sectioned endless solenoid 

 was 13 J cm., and the solenoid had, therefore, very nearly 3*5 turns 

 per cm. of mean perimeter. When immersed in liquid oxygen a coil 

 of this kind will carry a current of 50 amperes. When a current of 

 A amperes is sent through this coil the mean magnetising force in 

 the axis of this solenoid is, therefore, represented by 4*375 times the 

 current through the wire, hence it is clear that it is possible to produce 

 in the interior of this solenoid a mean magnetising force of over 

 200 C.Gr.S. units. This primary coil had then wound over it, in two 

 sections, about 400 or 500 turns of No. 26 silk-covered copper wire to 

 form a secondary coil. The primary and secondary coils were sepa- 

 rated by layers of silk ribbon. The exact number of turns was not 

 counted, and as will be seen from what follows it was not necessary 



