Since I made my first communication to this Society on Dust, Fogs, and Clouds, most of the experiments have been repeated under different conditions.

Taking advantage of the late extremely cold weather, the apparatus was placed in the open air, and experiments made with it, the temperature of the air at the time being 8° Fahr. The result was the same as at higher temperatures. Cloudy condensation with dusty air; no condensation with filtered air.

The experiment in which dustless gas was burned in dustless air was repeated. The glass jet which was used for burning the gas in the first experiment, being now replaced by a platinum one, as it was thought possible the dust produced when the glass jet was used might be the result of the decomposition of the glass by the heat. Before makiug the experiment, the platinum jet was highly heated, to cleanse and make it inactive. The result, however, was as before. Dense fogging whenever the gas was lit, and the fogging continued so long as the gas was kept burning.