Brown — Subsidence of Oscillations of Iron Wires and Alloys. 403 



scale, tliat is the division corresponding to an angular twist of the free end 

 of the wire of about ./zi'e degrees. 



Tabi.e V. 



The low and high chromium wires and the wire containing nickel behave 

 like ordinary iron wire, that is, the damping curve obtained witli the alter- 

 nating magnetic field in each case lies Moio the curve obtained with the 

 corresponding direct magnetic field, whereas the reverse is the case with the 

 wire containing 5'19 per cent, of chromium. It vi^ill be seen also that the 

 A.O. damping curve for this latter wire is identical with the one obtained 

 with the wire containing higher chromium : in fact, added chromium seems to 

 diminish the damping in I).0. fields, but only up to a certain percentage of 

 chromium in A.O. magnetic fields. This wire, however, has a considerable 

 amount (1"88 per cent.) of other impurities, which no doubt masks the effect 

 of damping of torsional oscillations when A.C. magnetic fields are applied. 



Vestalin is the trade name of a wire which seems to be practically the 

 same material as an alloy whose physical properties — thermal, electrical, and 

 magnetic — were investigated from seven to fii;'teen years ago in the Royal 

 College of Science by Sir W. F. Barrett, f.e.s., and the present writer, and 

 was then known as No, 1287L, a nickel steel containing about 25 per cent, of 

 nickel.' 



The main constituents^ of the specimen of vestalin under test are 

 Fe = 75'63 per cent., Ni = 23' 13 per cent., and it has the peculiar physical 

 property that it cannot be made mechanically softer by heating to a briglit- 

 red heat by means of a Bunsen flame, and then allowed to cool slowly. The 

 wire was tested for simple rigidity by three different methods and when in 



1 Scient. Trans. Roy. Dub. Soc, Series II, vol. vii, pp. 67-126, 1900; vol. viii, pp. 109-126, 

 1904 ; vol. ix, pp. 59-S4, 1S07. 



* The determinations of the principal constituents of Vestalin and Nickelin were done in the 

 chemical laboratory of this College, by Mr. G. van. B. Gilraour, a fourth-year research student in 

 chemistry. 



