TJIIE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



SEPTEMBER 1868. 



XXII. On the Polarization of Heat at 100° C, and on the Mo- 

 tion accompanying Heat -conduction. By Professor Magnus* . 



IN a former essay on the polarization of heat, aud on its pas- 

 sage through parallel plates t, it has been already shown 

 that the heat radiated from a red-hot plate of platinum at an ob- 

 lique angle only comes in part from the surface, another portion 

 being radiated from the interior. This fact was deduced as a 

 consequence of the polarization of the heat radiated from such a 

 surface. Eor since the plane of polarization has the same posi- 

 tion as that of light refracted at a certain angle, we are com- 

 pelled to assume that, at all events, one portion of the emergent 

 rays suffers a refraction at the surface ; and in order that this 

 may be the case, the heat must come from the interior of the 

 plate. Since, however, this polarization takes place according 

 to the same laws as that of light, we are further compelled to 

 conclude that the propagation of the heat in the interior takes 

 place in the same manner as that of light, namely in transverse 

 oscillations. In the above-mentioned publication it was asserted 

 that the conduction of heat depends upon this species of motion. 

 This assertion, however, was only based upon the fact that the 

 motion which is called heat cannot be of two kinds, and that, if 

 its propagation through air, vacuum, or any other diathermanous 

 substance takes place by means of transverse oscillations, its pro- 

 pagation in the interior of such bodies as are not diathermanous, 

 which propagation we call conduction, must be of the same 

 nature. 



This conclusion could not be drawn with certainty, because it 



* Monatsbericht der koniglich preussischen Akademie der Wissenschaften 

 zu Berlin. Marz 1868. 



t Monatsbericht, 1866, p. 62. 

 Phil. Mag. S. 4. Vol. 36. No. 212. Sept. 1868. M 



