IN December 1881 my attention was casually called to the popular superstition that sunlight puts the fire out. Returning from a walk I had found the blinds of my sitting-room closely drawn, for the benefit, as I was told, of the fire, which was low. On my appearing somewhat sceptical about the use of this proceeding, my landlady cited the above-mentioned superstition as a well known fact. For her benefit and instruction I made the poker red hot, and focused the sun's rays on it with a bull's-eye, showing her that, though the bright light prevented the red heat from being seen, it had not extinguished it, and was, moreover, capable of making a smaller piece of metal red hot. But I was myself so struck with the power of even the December sun in overcoming the light of the most highly incandescent body, that I determined to make further experiments. Even the intense glow produced by heating in the blowpipe flame a small piece of chalk, though it was sufficient to light up the whole room, entirely disappeared in the sun's rays. This led me to ask what would be the result of testing the sun's light in the same way against that of a flame. If, according to the older theory, luminous flame consists of incandescent solid particles, then I should expect that these would behave under the strong light exactly as the white-hot iron did, while, on the other hand, if as some have maintained the white light of a flame proceeds from gases of great vapour-density, then I might expect results which, if not different, would be at least interesting.