Prof. Forbes on the Refraction and Polarization of Heat, 29 1 



(which at first was zero), by the depolarizhig influence of the 

 crystal, is equal to that lost by the ordinary pencil. 



Q5, That the same law holds in the case of heat, the expe- 

 rinients, of which the followin<r is a brief summary, seem to 

 indicate. The coincidence has generally been more perfect, 

 as the steadiness of the source of heat admitted of more accu- 

 rate comparison. The indications in the same line are alone 

 intended to be compared, as they are expressed in degrees of 

 the multiplier, the absolute amount of which would vary in 

 different experiments. The interposed film of mica No. 1 . 

 is that mentioned in (54?), as giving a red of the second order 

 when placed between the polarizing and analysing })lates 

 crossed ; the film No. 2. gave a plum red of the first order 

 under the same circumstances. 



[To be continued.] 

 2P2 



