XXIII. On radiation from dull and bright surfaces

In connection with an investigation on heat radiation which I have been carrying on for some time past, and on which I recently presented a communication to the Royal Society, I have had occasion to examine the important results obtained by Mr. Mortimer Evans on the radiation of light and heat from bright and dull surfaces when incandescent (‘Roy. Soc. Proc.,’ vol. 40, 1886, p. 207); and I have repeated and verified some of his experiments. Mr. Evans experimented on carbon filaments of incandescent lamps; and in calculating, for my own use, the resistances of the filaments at different degrees of incandescence I was led to an unexpected result, and hence to an investigation of which I desire just now to offer a preliminary notice.