288 Prof. A. Gray and Mr. A. Wood. Effect of a [Mar. 12, 



and then plunging it into cold water ; when it was found to be softer 

 than it was originally. For the original wire, for example, the modulus 

 of rigidity was 7'97 x 10 C.G.S., for the wire as drawn down it 

 was 8*06 x 10 C.G.S., and for the annealed wire it was 7*81 x 10 

 C.G.S. Curve II is the curve for the annealed wire corresponding to 

 curve I, that is, showing the differences after forty oscillations of 

 the amplitudes of oscillation of the wire under the various fields 

 and the amplitude with zero field. The latter amplitude it is to be 

 remembered was the greater. 



After annealing and re-drawing had been performed in succession, 

 the wire gave curve III, and its rigidity modulus was 8 '3 18 x 10 

 C.G.S. 



These three curves make it clear that the effect of the magnetic 

 field on the internal viscosity of a nickel wire depends very largely on 

 the hardness of the metal, as, of coarse, we should expect. 



The progressive modification of the groups of molecular magnets by 

 the magnetic field is opposed by the greater resistance introduced by 

 the hardening, and the changes due to the field are not produced. In 

 the annealed condition the wire has its groups much more at liberty 

 to take up a new arrangement, and this is shown also, of course, by 

 the smaller magnetic susceptibility in the hardened condition. 



Curves I a , II a , give the results as in I and II, but after twenty 

 oscillations. It will be observed that while ll a is above II up to and 

 beyond the field of maximum difference of amplitude, and is then below 

 II, curve I a is below II throughout its entire course. 



Effect of Drawing Down on the Iron Wire. — This is shown in fig. 2, in 

 which the ordinates and abscissae represent the same quantities as do 

 the ordinates and abscissae of the curves in fig. 1, after twenty oscil- 

 lations in each case. The amplitude for iron, it is to be remembered, 

 is greater with field than with no field. The steep rise of curve I, and 

 the horizontality of the remaining part, show the fact noted in the 

 former paper, that the effect of the magnetisation in iron is attained 

 with low fields, and that higher then produce little further effect. 



After the results shown in curve I had been obtained the wire was 

 drawn through two holes of the draw plate, and after this treatment 

 gave curve II. This curve is lower and rises less sharply than I, 

 showing that the internal viscosity of the wire was not so much 

 affected by the magnetic field as previously. 



The drawn wire was then annealed, and gave curve III, which does 

 not differ much from I. Further drawing down resulted in curve IV, 

 which is practically a straight line, that is, the difference is now nearly 

 proportional to the field. Ee-annealing of the now much thinner wire 

 gave curve V, which shows a very distinctly greater effect of magneti- 

 sation on viscosity than ever before. The repeated drawing and 

 annealing process thus seems to result in the finally annealed wire in 



