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For this purpose, I made a special transmitter, which consists 
of a shallow wooden box, having a disc of brass in its bottom, 
to which one electrode is attached. Above this is placed a 
thin layer of the red phosphorus, and the whole enclosed by very 
flexible brass plate, bound down round the edges, and having the 
other electrode attached to it. A mouthpiece is arranged so as to 
direct the voice against the centre of the thin brass plate. When 
this transmitter is joined up in circuit with a telephone, singing 
and articulation are distinctly reproduced. When a battery is in- 
cluded, the sounds come out of the telephone with singular clear- 
ness and loudness; and there is also a very remarkable want of any 
rattling, such as is usual with an ordinary microphone. I have 
also found that the cell, which is really a form of loose contact, can 
act as a receiver as well as a transmitter ; but my experiments on it 
in this capacity are as yet incomplete. 
4. Dust, Fogs, and Clouds. By Mr John Aitken. 
( Abstract .) 
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, how- 
ever, was as before. Dense fogging whenever the gas was lit, and 
the fogging continued so long as the gas was kept burning. 
The experiment for detecting small quantities of dust has also 
