On Magneto- Electric Induction. 449 



the pile 420 millims.; surrounding temperature 24°*0 ; read- 

 ing on the galvanometer 31*6 divisions. 

 Calculated for the distance 6*1 + 107*17, 



?/ 1 =13-0 divisions, y= g^- =22*25; 



the formula gives 



T==2440°, £=2167°. 



Second experiment. — In this experiment I obtained a large 

 deflection on the galvanometer, but the cylinder shone very 

 brilliantly. Distance from the pile 420 millims. Deflection 

 (mean of three experiments) = 42*0 divisions. At the dis- 

 tance 107*17 + 6*1 millims. we should have had 



1 7*A& 



y 1 = 17*68 divisions, y= ( ^gj = 29 ' 58 ? 



T=2670°, £=2397°. 



These two numbers, 2167° and 2397°, although higher than 

 those obtained in the first series, will not appear too high if we 

 reflect that platinum immediately melted before the flame, and 

 that the light emitted in the experiments of the second series 

 was considerably greater than that emitted in those of the 

 first. I think that all who have made researches of this nature 

 will consider the results obtained to be satisfactory, and that 

 there is reason to conclude that the formula 



y=mET 2 (J-0)-m(J-0), 



which has stood the tests so well up to 2000°, can confidently 

 be applied to experiments made at higher temperatures, and 

 that it can be employed to find the temperature of the sun. 



[To be continued.] 



LIV. On Magneto-Electric Induction. By Frederick 

 Guthrie and C. V. Boys, Assoc. R. School of Mines*. — 

 Parti. 



[Plate XIIL] 



IT is well known that the electric currents caused in a con- 

 ductor by relative motion between that conductor and 

 a magnetic pole are in such a direction as to impose a drag 

 upon such motion. An ideal friction (that is, one without 

 recoil) is called forth ; and, accordingly, in the experiments 

 sometimes called Arago's such current-friction exhibits itself 

 in the pursuit of the moving element by the one which is free 

 to move, though originally at rest. Again, the same current- 

 * Communicated by the Physical Society. 



