Breath Figures

Abstract

ON reading Lord Rayleigh's short article on breath figures in NATURE of May 25 and finding he was not satisfied with the explanation I offered of them, I thought it would be as well to see if it was possible to get some further information on the subject. For this purpose I repeated the experiments with variations in the conditions. As the writer of the article seemed to think that the hot gases act in some way in cleaning the surface of the plate, the experiments were now made at lower temperatures. In place of the blow-pipe flame a Bunsen burner was used, and in order to protect part of the surface from the action of the hot gases, the plate was supported on two thick iron bars, so as to confine the action of the gases to the narrow space between them, and further, the glass plate was kept as cold as possible. It was intended to use ice for this purpose, but it was found that it kept the under surface always dewed, so that the gases could not come into contact, with the plate. Wet blotting-paper placed on the upper surface was found to keep the plate cool enough, and yet not so cold as to cause the deposition of dew. It was found that it was not necessary to pass the plate through the flame to get the breath figures; it could be held some distance above it with a similar result, but, as might be expected, a longer time was necessary than when in the flame, not only on account of the lower temperature of the gases, but also on account of the plate getting heated by the longer exposure.