46 Note on M. Mascart's paper, u On Magnetization." 



mentioned metals yield with iodide of ethyl only zinc ethyl, 

 a tin alloy should give such large quantities of tin tetrethyl. 

 This may be accounted for perhaps by the greater stability 

 of the tin tetrethyl at high temperatures, the organo-metallic 

 compounds of bismuth, lead, aluminium, and antimony all 

 decomposing when strongly heated. 



Y. Note on M. Mascart's paper, " On Magnetization" * 

 By E. F. J. Love, B.A., Demonstrator of Physics in the 



Mason Science College, Birmingham f . 



IN the above-mentioned paper, M. Mascart draws attention 

 to the fact that the values of the coefficient of magnet- 

 ization, as determined by using long cylinders, differ from 

 those obtained by the employment of rings ; and tries to 

 demonstrate that " a special phenomenon is produced in the 

 case of closed rings which exaggerates the effects of induc- 

 tion/' 



Without presuming to question M. Mascart's investigations, 

 I may be allowed to point out that the facts admit of an 

 entirely different and much simpler explanation. 



Calling the two values of the magnetization-coefficient 

 determined with the help of bars, / and f ly as is done by 

 M. Mascart, I may first point out that f\ is measured by 

 finding the magnetic induction at the centre of the bar, while 

 /is determined by the magnetic moment, which depends on 

 the distribution of magnetic induction throughout the bar. 

 In all cases the induction through the central section is the 

 greatest, owing to lines of induction leaving the bar all along 

 its length, and not all going right through to the ends ; the 

 effect of this is to diminish the apparent value of the magneti- 

 zation-coefficient as determined from the magnetic moment. 

 The extent to which the induction-lines escape is very 

 surprising, as the following example will show : — 



A rectangular bar of soft iron was bent into a ring, and 

 turned in the lathe to a true circle, 10 centim. in diameter. 

 It was then cut into tw r o halves along a diameter, and the cut 

 ends worked to true planes. On each half a primary coil of 185 

 turns was wound, and these were connected together, giving a 

 primary of 370 turns covering up the iron. Two secondary 

 coils of 10 turns each were then wound on, one near the end 

 of one of the semicircles, the other forming a spiral extending 

 over the surface of the same semicircle. The two electro- 



* Phil. Mag. June, 1886, p. 515. 

 t Communicated by the Author, 



