^{page 240 note *} Proc. Roy. Inst., vol. vi. p. 3, 1870Google Scholar; also Essays on the Floating Matter in the Air, p. 5, Longmans, Green, & Co., 1881Google Scholar.

^{page 240 note †} Paper read before Royal Society, December 21, 1882; also Nature, vol. xxviii. p. 139Google Scholar.

^{page 243 note *} In the figs, the white surface represents the light-reflecting dusty air, while the black represents the transparent air, free from reflecting particles.

^{page 243 note †} The only reason I can imagine for this difference between Dr Lodge&s results and mine is that he worked with more powerful sources of illumination than I did. He used either the sun's light, an oxyhydrogen lamp, or a Serrin arc-lamp, while I only used gas. Now one result of this difference would evidently be that the illuminating beam used by him would have a much greater heating effect than the one used in my experiments, and would therefore heat the surfaces under examination. I found this effect even with gas. If the body had a small capacity for heat, it was only necessary to keep the light focused on it for a short time to heat it sufficiently to cause a clear space to form over the part where the light acted.

^{page 258 note *} The amount of dust breathed by invalids at the two places will not be greatly different, as most of their time is spent in the house, and the air in the rooms at the two places will be nearly equally dusty. The higher temperature inside will slightly reduce the thermal effect, but will not diminish the rate of evaporation.