490 PROCEEDINGS OP THE AMERICAN ACADEMY. 



Investigations on Lioht and Hkat. mabk and published wholly or in part with 

 Appropriation from the Rumford Fund. 



XXII. 



CONTRIBUTIONS FROM THE PHYSICAL LABORATORY OF THE 

 MASSACHUSETTS INSTITUTE OF TECHNOLOGY. 



XLIIL — EXPERIMENTS ON THE RELATION OF 

 HYSTERESIS TO TEMPERATURE. 



By Frank A. Laws and Henry E. Warren. 



Presented by Charles R. Cross, October 10, 1894. 



This paper gives an account of some experiments to determine the 

 effect of temperatures much above the normal on the dissipation of 

 energy by hysteresis in a specimen of steel. 



At the time of the beginning of this research, in February, 1894, 

 there were no complete studies of this subject known to us. A casual 

 reference is to be found in the Proceedings of the American Institute of 

 Electrical Engineers, Vol. VII. p. 325, 1890, by Prof. Harris J. Ryan. 

 The tests there referred to were made on a cast-iron rinw. The maxi- 

 mum temperature employed was 360°. The details of the measure- 

 ments are not given. A short paper by Dr. Wilhelm Kuntz appeared 

 in the Electrotechnische Zeitschrift, Vol. XIII., May 6, 1892. In 

 this Dr. Kuntz showed that the hysteresis loss decreased with rise 

 of temperature. A second paper by the same author appeared in 

 the Electrotechnische Zeitschrift, Vol. XV., April 5, 1894. The 

 magnetometer method was used by Dr. Kuntz in this work. In this 

 paper tests of several ferrous materials are given, as well as some on 

 a specimen of nickel. 



At the outset of this research it was decided that alternating cur- 

 rents should be used, and that the losses should be determined by a 

 Wattmeter, thus reducing the time required for observations to a mini- 

 mum. The instrument which we designed and used is shown in 

 Figure 1. We have decided to call the arrangement a Watt-balance. 

 Mr. A. E. Kennelly has given in the Electrical Engineer, December 21, 



