“A series of delicate and tedious experiments on heat have conducted me to the following results, which will be fully discussed in a paper shortly to be laid before the Society.

“1. An entire confirmation of my previous statement, that different kinds of heat are differently susceptible of polarization by transmission through a given bundle of mica plates; heat from obscure sources being less polarizable than that from luminous sources. I considered my investigations incomplete until I had proved not only that my former experiments had led me to correct results, but also why the only other person who I believe has attempted to obtain them was led to the opposite conclusion, as stated by M. Melloni in the Annales de Chimie for May 1837, namely, that all kinds of heat are equally susceptible of polarization. I have at length discovered, in the description of M. Melloni's method, the cause of his failure to detect this fact.