OF A.RTS AND SCIENCES. 205 



Intestigatioks on Light and Heat, published with Appropeiation prom thk 



komford fcnd. 



XII. 



CONTRIBUTIONS FROM THE PHYSICAL LABORATORY OF 

 HARVARD UNIVERSITY. 



ON THE HEAT PRODUCED IN IRON AND STEEL BY 

 REVERSALS OF MAGNETIZATION. 



By John Trowbridge and Charles Bingham Penrose. 



Presented May 29th, 1883. 



The following experiments were made with the object of testing cer- 

 tain deductions that seem to follow from Weber's theory of magnetism. 

 The test applies to any theory which regards magnetization to be due 

 to a regular change of position or rotation of the molecules. Weber's 

 theory, doubtless, has strong experimental evidence in its favor, such 

 as the experiments of Beetz,* showing a maximum intensity of mag- 

 netization in iron deposited by electrolysis in a magnetic field. But 

 the experiments of Siemens! indicate that the theory must at least be 

 modified; and our experiments upon the heat developed by rapid 

 magnetization and reversals of magnetization seem to show that mo- 

 lecular work — at least of the kind supposed by Weber — does not 

 play so strong a part in magnetic phenomena as has generally been 

 supposed. 



Various observers have measured the heat which they supposed to 

 be due to magnetization and to reversals of magnetization. Thus 

 Joulet revolved a piece of iron, contained in a tube of water, between 

 the poles of a horseshoe magnet, and measured the rise of temperature 

 and the work done. Van Breda § placed an iron cylinder in a coil of 

 copper wire, bored a hole in the iron, and placed the bulb of a spirit 

 thermometer in this hole. On passing a continuous current of elec- 

 tricity through the coil, no increase of temperature was denoted by the 

 thermometer. When, however, the current was made and broken 



* Fogg. Ann., cxi., 1860. 



t Ann. Phys. Chem., 1881. 



t Phil. Mag., xxiii. 263, 347, 435, 1843. 



§ Compt. Rend., xxi. 961 ; also, Pogg. Ann., Ixviii. 552, 1846. 



