Peirce — Induction Coefficients of Hard Steel Magnets. 351 



different lengths, but all 0*95'^°'^ in diameter. It soon appeared 

 that the hardening was not sufficiently uniform to serve my 

 purpose, so I reheated and hardened all these pieces. This 

 process, as was to be expected, injured the steel by increasing 

 the induction coefficients and decreasing the permanent mag- 

 netic moments of the seasoned magnets. This appears from 

 measurements given in Table Y, in which the first four columns 

 apply to all the pieces, but the last column only to the Jessops 

 and Crescent steels, which were almost exactly alike after the 

 rehardening. The permanent magnetic moments of the Stubs 

 steel magnets were only about half those of corresponding 

 magnets made of the other steels. The results of observations 

 upon numerous pieces of Jessops square and fiat tool steel 

 appear in Tables YI and YII. 



I have tested a number of magnets made of the "special 

 magnet steels" of different makers. These all had, of course, 

 relatively high permanent moments, but most of these steels 

 are difficult to work and I have not yet been able to procure a 

 sufficient quantity of any one of them, in shape suitable for 

 the making of dellecting magnets, to enable me to compare 

 the advantages of such magnets over those made of tine tool 

 steel. 



Table 1.— Magnets made of Round Polished Drill Rod. 



Brand. 



Crescent 

 Stubs... 

 Crescent 

 Stubs . - . 

 Crescent 

 Stubs... 

 Crescent 

 Stubs... 

 Crescent 

 Stubs . . . 

 Crescent 

 Stubs - . . 

 Crescent 

 Stubs . _ . 

 Crescent 

 Stubs . . . 

 Stubs . . . 

 Stubs . . . 

 Stubs... 

 Stubs... 

 Stubs... 

 Stubs... 

 Stubs . - . 



Lengtli in centime- 

 ters. 



Diameter in centi- 

 meters. 



12 



0-64 



12 



0-64 



12 



48 



12 



0-4 8 



12 



0-30 



12 



0-30 



10 



64 



10 



0-64 



10 



0-48 



10 



0-48 



10 



30 



10 



0-30 



8 



0-64 



8 



64 



8 



0-48 



8 



0-48 



6 



80 



8 

 10 



0-80 

 0-80 



12 



0-80 



15 

 18 

 20 



0-80 

 0-80 



0-80 



a _ oj J: oi 

 5 a. ^-r. 



!a)c-*-3 si's 



(., iU c =1 c tc 

 oi OS-- :s n,^ 



+i "^ i '^.^ a 

 fl ^ u 0. s 



I'd .2 2^.2 



0-23 



20 



0-21 



18 



0-22. 



0-18 



0-19 



0-19 



0-19 



0-18 



0-20 



0-18 



0-20 



018 



0-19 



0-18 



0-15 



0-18 



0-20 



022 



0-24 



0-26 



0-27 





27 

 27 

 31 

 30 

 36 

 36 

 25 

 24 

 30 

 27 

 30 

 25 

 20 

 16 

 21 

 19 

 10 

 12 

 14 

 17 

 21 

 28 

 35 



ee c « "" ^ j= 0) 

 ^- B a i cj- d 



^6 





0-009 

 0-008 

 0-007 

 006 

 006 

 0()5 

 008 

 0-0()8 

 0-006 

 0-007 

 0-007 

 007 

 0-010 

 0-011 

 0009 

 00(.9 

 0-015 

 0015 

 0-014 

 0-013 

 0-011 

 0009 

 0-0U8 



