THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



NO V EMBER 1862. 



XLIV. On the Thermal Phenomena which accompany the changes 

 in volume of Solid Bodies, and on the corresponding Mechanical 

 Work. By M. Edlund*. 



IT follows directly from the first principles of the mechanical 

 theory of heat, that the absorption or disengagement of heat 

 which accompanies any modification of a body, does not depend 

 solely on this modification itself, but on the external mechanical 

 work which may be created or destroyed at the same time as this 

 modification takes place. The experimental verifications of this 

 general theorem are, with reason, classed amongst the most con- 

 vincing proofs which can be given of the great principle of the 

 equivalence of mechanical work and heat. Thus, in late years, 

 physicists have laid great weight on Hirn's experiments on the 

 heat disengaged by the condensation of the steam of a machine 

 in motion, and on the experiments of M. Favre on the total heat 

 disengaged by the solution of an equivalent of zinc in a voltaic 

 circuit comprising an electro-magnetic motor. M. Edlund has 

 proposed to himself the task of investigating, from the same 

 point of view, a thermal phenomenon as yet little studied — the 

 disengagement or absorption of heat which accompanies the con- 

 traction or elongation of a metal wire. 



The principle of the experiments consisted in measuring suc- 

 cessively, 1st, the quantity of heat absorbed by a wire which is 

 elongated during the time in which a weight suspended to its 

 extremity descends by a given quantity ; 2nd^ the quantity of 

 heat disengaged by the same wire when it became shorter by the 



* Translated from an abstract, published by M. Verdetin the Annates de 

 Chimie et de Physique, February 1862, of the original paper, which appeared 

 in Poggendorff's Annalen, vol. cxiv. p. 1. 



Phil. Mag. S. 4. Vol. 21. No. 162. Nov. 1862. Z 



