and placed over a sink. Alongside of this
faucet there is a double gas burner, which may be connected with
furnaces and heating apparatus by means of rubber tubing. A special
hall, with draught and ventilation, is set apart for precipitations by
sulphureted hydrogen and the preparation of chlorine and other
ill-smelling and deleterious gases. The great amount of light and
space provided secure the best of conditions of hygiene to this fine
and vast laboratory, where young people have all the necessary
requisites for becoming true chemists.--_La Nature._

* * * * *

DUST-FREE SPACES.[1]

[Footnote 1: Lecture to the Royal Dublin Society by Dr. Oliver J.
Lodge, April 2, 1884.]

Within the last few years a singular interest has arisen in the
subject of dust, smoke, and fog, and several scientific researches
into the nature and properties of these phenomena have been recently
conducted. It so happened that at the time I received a request from
the secretary of this society to lecture here this afternoon I was in
the middle of a research connected with dust, which I had been
carrying on for some months in conjunction with Mr. J.W. Clark,
Demonstrator of Physics in University College, Liverpool, and which
had led us to some interesting results. It struck me that possibly
some sort of account of this investigation might not be unacceptable
to a learned body such as this, and accordingly I telegraphed off to
Mr. Moss the title of this afternoon's lecture. But now that the time
has come for me to approach the subject before you, I find myself
conscious of some misgivings, and the misgivings are founded upon this
ground: that the subject is not one that lends itself easily to
experimental demonstration before an audience. Many of the experiments
can only be made on a small scale, and require to be watched closely.
However, by help of diagrams and by not confining myself too closely
to our special investigation, but dealing somewhat with the wider
subject of dust in general, I may hope to render myself and my subject
intelligible if not very entertaining.

First of all, I draw no distinction between "dust" and "smoke." It
would be possible to draw such a distinction, but it would hardly be
in accordance with usage. Dust might be defined as smoke which had
settled, and the term smoke applied to solid particles still suspended
in the air. But at present the term "smoke" is applied to