PEIRCE. — MAGNETS OP HARDENED CAST IRON. 



709 



the moments 3470, 2500, and 4190 approximately : this steel was in our 

 hands, therefore, not so good as the Seel)ohm and Dickstahl Special, The 

 special magnet steels can be bent or formed, but cannot be heated hoi 

 enough for welding without spoiling the material for making magnets. 



In Figure 2 the results of observations made by Mr. John Coulson 

 and myself upon round cast-iron rods 18 cm. long and 0.95 cm. in diam- 



Figure 2. 



eter are shown. The rods were magnetized in a solenoid, of 4927 turns 

 in a length of 980 millimetres, placed with its axis horizontal and per- 

 pendicular to the meridian, and the relative moments, at different times, 

 of the rod under investigation were determined from the deflection of a 

 mirror magnetometer placed outside the solenoid in tlie Second Position 

 of Gauss with respect to the magnet. The abscissas represent the field 

 (in tens of gausses) to which the rod is subjected by the current in the 

 solenoid; the ordiuates represent the corresponding magnetic moment of 



