Brown — Subsidence of Oscillations of Iron Wires and Alloys. 401 



Table IV. 



The heating of the wires dimiuishes the amplitude of the 70th vibration 

 of SCI. considerably in both the D.C. and A.C. fields; but it lias no effect 

 on the stalloy in the D.C. field, though it diminishes the 70th amplitude in 

 the A.C field by about 12 per cent. 



The full-line curve refers to S.C.I., and the broken-line curve to stalloy. 



The table and curves show that there is much less damping of torsional 

 oscillations in the stalloy than in the S.C.I. wire. The stalloy wire in t)ie 

 soft physical state could not be fatigued at all even by the application of an 

 alternating magnetic field for one hour and a half, whereas the S.C.I, wire 

 in tlie soft state had a maximum fatigue 0'22 with the application of the 

 alternating magnetic field for about half an hour. Tliis silicon iron alloy 

 when submitted to a special heat treatment which prevents it from ageing is 

 used in electrical engineering work under the trade name stalloy ; but this 

 specimen of wire under test has not been so treated, as is shown by its ability 

 to be fatigued when in the harder physical state. 



About four years ago, Sir E. A. Hadfield, f.r.s., of the Hecla steel works, 

 Sheffield, presented the author with a collection of about a dozen alloys of 

 iron in the form of wires of size No. 19, a few of which were found suitable 

 for these experiments. 



The chemical analyses of the specimens were done in the chemical 

 laboratory attached to the Hecla works, and the wires were all subjected 

 to the same heat treatment, namely, tliey were heated to a temperature 

 of 800° C. and allowed to cool in the air so as to prevent scaling. 



SCIENT. PEOC. K.D.S., VOL. XIV., NO. XXXH. 3 T 



