The Philosophical magazine; a journal of theoretical, experimental and applied physics . the inside layer was muchweaker, although the insulation was still perfect when the wirewas in place. I can only account for this by the electric currentgenerating heat in the wire, which was unable to pass outwardbecause of the outside layer and also of the pieces of paperwhich were used to separate the layers of wire; hence the ringat high magnetizing-powers must have been at a somewhathigher temperature than the bath, to an amount which it is im-possible to estimate. It is probable that it was not very
The Philosophical magazine; a journal of theoretical, experimental and applied physics . the inside layer was muchweaker, although the insulation was still perfect when the wirewas in place. I can only account for this by the electric currentgenerating heat in the wire, which was unable to pass outwardbecause of the outside layer and also of the pieces of paperwhich were used to separate the layers of wire; hence the ringat high magnetizing-powers must have been at a somewhathigher temperature than the bath, to an amount which it is im-possible to estimate. It is probable that it was not very great,however; for at this high temperature continued for hours itrequires but little increase of heat to finally destroy the can, however, tell the direction of the error. We see, on comparing Tables I. and II. with Table III., thegreat effect of heat on the magnetic properties of nickel. Wesee that for low magnetization the permeability is greatly m-a-eased, which is just opposite to what we might expect; but onplotting the curve we also notice the equally remarkable fact,. 1. Curve at 15° C. 2. Curve at 220^ C. that the maxinnim of magnetization is decreased horn -8=G3400o^. 3 = 49,],0 to ^i^=190()() or :s = 3H00. This curious result isshown in the annexed figure, where we see that for low magne- and Maximum of Magnetism of Nickel and Cobalt. 331 tizing-forces ^ is increased to about three or four times its valueat 15^ C, and the maximum value of yii is increased from 222to 315. When 53 has a value of 32,000, ft is not affected bythis change of temperature, seeing that the two curves coincide;but above that point /u, is less at 220° C. than at 15° C. Inother words, if nickel is heated from 15° C. to 220° C, the mag-netization of nickel will increase if the magnetizing-force is small,hut will decrease if it is large. It is impossible to say at presentwhether increase of temperature above 220° will always produceeffects in the same direction as below it or not. T
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