M. MELLONI ON THE POLARIZATION OF HEAT. IGl 



tion of refracted light is perpendicular to the plane of refraction^ 

 or of reflection, at which reflected light is polarized. On the 

 other hand, the rays polarized perpendicularly, to the plane of 

 reflection, are no longer capable of being reflected from the la- 

 minae of glass at 35° 25', but penetrate into its substance without 

 undergoing any diminution of intensity. Therefore, the refracted 

 hght in the interior of the pile, being completely polarized in a plane 

 perpendiculai' to that of the refraction, after traversing a certain 

 number of laminae, and arriving upon the surfaces of the suc- 

 ceeding laminae at an angle of 35° 25', will experience the same 

 negative effect ; viz. it will traverse them all without suffering 

 any loss by reflection. But this entire transmission cannot be 

 effectuated at any other inchnation, because, in that case, the 

 luminous rays which are penetrated at a certain depth of the pile, 

 and which become polarized by refraction, then undergo only an 

 effect of incomplete polarization, by the action of the reflecting 

 surfaces of the remaining laminae, which consequently resume a 

 portion of their ordinaiy activity, which increases in proportion to 

 its further removal, in either direction, from 35°* 25'. The losses of 

 the luminous pencil will therefore follow the same progression, so 

 that the maximum intensity, in transmitted light, will necessarily 

 occur at the angle of complete polarization. 



Thus the known fact of luminous polarization by reflection 

 and refraction, and the equally known fact of the peq^endicula- 

 rity of the planes of these two polarizations, necessarily conduct 

 to the consequence, that light transmitted by a pile of numerous 

 diaphanous laminse attains a maximum intensity at the angle of 

 complete polarization, produced by reflection. 



Vice versa, starting from the observation of this maximum, in 

 the quantity of light transmitted at different inclinations of the 

 pile, we deduce from it the existence of the two polarizations, the 

 angle at which polarization by reflection takes place completely, 

 and the perpendicularity of the two planes at which the light is 

 found polarized by virtue of the forces of reflection and refrac- 

 tion. 



Now, this is precisely the case with the transmission of ra- 

 diant caloric by piles of mica ; for, by examining the series of 

 numbers contained in the first columns of the last six tables, it 

 will be seen that the transmission by the series of parallel la- 

 minae increases with the inclination, up to an angle comprised 

 between 33° and 35°, and decreases again beyond that limit. 



