Magnetic Permeability of various Alloys of Iron. 123 



A correction is of course necessary for the demagnetising effect of the ends in all 

 these highly permeable specimens; see Note A at end. Experiments arein progress 

 with more slender and carefully turned rods and rings of silicon iron, and the best 

 iron (S. C. I.), in order to compare more accurately their magnetic properties; as 

 far as they have gone, these confirm the general results above stated. The com- 

 paratively small susceptibility of iron to feeble magnetic forces has been long 

 known, but we believe that hitherto no other substance has been found better 

 than iron in this respect. 



The coercive force of the silicon steel is about one half that of the best iron 

 S. C. I, its retentivity is also much less, and the hysteresis loss per complete 

 magnetic cycle is therefore much smaller. The B and H curves of S. C. I. and 

 the 5i per cent, silicon steel, were carefully plotted, their areas measured, and 

 the ergs dissipated per complete cycle, with a maximum magnetising force of 

 45 C. G. S. units, were found, with the following results : — 



Table XVIII. 



It is hardly necessary to point out the great importance of the above results 

 from a theoretical as well as practical point of view. We may add that these 

 silicon-iron alloys, as well as some of the manganese steels, manganese-nickel 

 steels, and tungsten steels are patented products. 



Some low silicon steels were tested by Mdme. Sklodowska Curie in her inves- 

 tigation on the magnetic properties of tempered steels. Mdme. Curie states that 

 " the presence of small quantities of silicon does not appear sensibly to alter the 

 magnetic ^jroperties of steel." * But in the table of results, given by this able 

 experimenter, it will be seen that a tempered steel, containing 1-28 per cent, of 

 silicon, has its coercive force reduced about 32 per cent, when compared with 

 steel containing the same percentage of carbon, but without silicon. 



The specimens employed by Mdme. Curie were those used by M. le Chatelier, 

 to which we have referred on p. 99, and consisted of short bars, whose length 

 was only twenty times their diameter ; the magnetic reaction of the ends was 



* See Bulletin de la Societe d^ encouragement pour l 



IHANS. EOr. BUB. SOC, N.S. VOL. Til., PAET IV. 



ie nationale, Janvier 1898, p. 53. 



