Alternating Current Magnetic Curve Tracer. 



Ill 



In either case, by means of one of the mirrors attached to the 

 I-magnetometer helix, we are enabled to record a displace- 

 ment, the rectangular components to which are independent 

 of each other, and accurately proportional to the intensity of 

 magnetization of the sample and the magnetizing force pro- 

 ducing that magnetization, at any point in the magnetic 

 cycle. 



Thus we have, in this magnetometer system of two simple 

 helices connected as described, the fulfilment of all the essen- 

 tial conditions for an instrument measuring the dissipation of 

 energy in either " static " magnetic cycles, or in " periodic " 

 magnetic cycles of any frequency. 



§ 4. Fig. 3 shows the form of the magnetic-curve tracer 



Fi<T. 3. 



now used in the Magnetic Observatory of Princeton Uni- 

 versity. It consists, first, of a solid wooden base of circular 

 shape, provided with levelling-screws. From this base arise 

 four vulcanite pillars, which support a vulcanite disk, having 



