oks. Dr.
Draper* has observed a similar difference between the chemical action
of light in New York and Virginia. This can be only explained by the
supposition that the intensity of the light and heat of these climes
interferes with the action of the ENERGIC rays on those sensitive
preparations which are employed.

* I would here take occasion to remark that our country man, Dr.
Draper, is very frequently quoted by Mr. Hunt in his "Researches."

LUNAR PICTURES--DRUMMOND LIGHT.

The Roman Astronomers state that they have procured Daguerreotype
impressions of the Nebula of the sword of Orion. Signor Rondini has a
secret method of receiving photographic images on lithographic stone;
on such a prepared stone they have succeeded in impressing an image of
the Nebula and its stars; "and from that stone they have been enabled
to take impressions on paper, unlimited in number, of singular beauty,
and of perfect precision." Experiments have, however, proved that "no
heating power exists in the moon's rays, and that lunar light will not
act chemically upon the iduret of silver."

It was at one time supposed that terrestrial or artificial light
possessed no chemical rays, but this is incorrect--Mr. Brande
discovered that although the concentrated light of the moon, or the
light even of olefiant gas, however intense, had no effect on chloride
of silver, or on a mixture of chloride and hydrogen, yet the light
emitted by electerized charcoal blackens the salt. At the Royal
Polytechnic Institution pictures have been taken by means of sensitive
paper acted upon by the Drummond Light; but it must of course be
distinctly understood, that they are inferior to those taken by the
light of the sun, or diffused daylight.

If our operators could manage to produce good pictures in this way they
would put money in their pockets, as many who cannot find time during
the day would resort to their rooms at night. I throw out the hint in
hopes some one will make the experiment.

I have learned, since the above was written, that an operator in Boston
succeeded a short time since in procuring very good pictures by the aid
of the Drummond Light; but that the intensity of the light falling
directly upon the sitter's face caused great difficulty, and he
abandoned it. This may, probably, be remedied by interposing a screen
of very thin tissue paper tinged slightly of a bluish color.

CHAP. XII.

ON COLORING DAGUERREOTYPES.

Nearly,