M. MELLON! ON THE POLARIZATION OF HEAT. 155 



is easily obtained, as has been seen above, by multiplying the 

 difference of the two forces corresponding to the parallel and 

 l^erpendicular positions by 100, and dividing the jjroduct by the 

 first of those two numbers. 



This polarized heat, or, in other terms, the heat which dis- 

 appears in the act of the intersection of the two planes of refrac- 

 tion, is neither destroyed nor absorbed, but simply reflected, as 

 occurs in the polarization of light. This may be proved by 

 taking two of our bundles, composed of twenty or thirty laminae, 

 which are to be inchned from 30° to 40° upon the axis of radia- 

 tion, and to receive at first a parallel and vertical direction. Af- 

 terwards withdraw the thermoscopic body from its place, and 

 dispose it laterally at the same distance from the posterior pile, 

 keeping it still turned towards it, but in such a manner that the 

 axis of its cylindrical envelope forms, with the anterior sheet, 

 an angle equal to that formed on the other side of the normal 

 by the incident calorific pencil. The effect of the reflection, 

 which should take place evidently in the direction of the ther- 

 moscopic body, is then extremely feeble, and the index of the 

 galvanometer scarcely departs a few degrees from its natural 

 position of equiUbrium ; for the heat transmitted by the first 

 pile arrives upon the second, and continues to be transmitted by 

 the remaining laminae, in consequence of the parallelism of the 

 planes of refraction. But if the anterior pile be turned in such 

 a manner as to place its plane of refi*action perpendicular to that 

 of the posterior pile, leaving all the rest in their previous state, 

 a considerable deviation is immediately manifested in the indi- 

 cating needle of the galvanometer, which proves a very abundant 

 reflection of heat upon the sm*face of the second pile : now, in 

 experiments on polarization, it is precisely when the two planes 

 of refraction are thus disposed, that a great portion of the heat 

 no longer reaches the thermoscope. 



The following are the eight tables. 



