SCIENTIFIC SUMMAEY. 
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mirror, for the experiments of Professor W. Allen Miller, F.R.S., show that 
polished metals do not all reflect the extra violet rays so perfectly as they 
reflect the visible rays. For instance, he found that speculum metal and 
polished steel reflect exactly the same rays of the spectrum, and give spectra 
on a photographic plate of exactly the same length each. But he also found 
that speculum metal gave an intense image for one-half only of the length 
of its spectrum, whilst steel gave a more intense image than any other metal 
throughout the whole length of the spectrum of the light reflected from its 
surface. These results point to the conclusion, that a steel parabolic mirror 
will enable a photograph to be taken more rapidly than can be done by 
speculum metal or silvered glass reflectors. The Mechanic's Magazine also 
states that Mr. Dallmeyer is making a special enlarging lens for producing 
magnified copies without loss of details : but we think this must be a mistake, 
inasmuch as it is not superior defining power which is required, so much as 
superior films to enlarge upon, more free from structural defects ; also the 
means of obtaining a much finer granular deposit of silver. 
Enlargements hy the Magic Lantern. — Mr. J. C. Leake has pointed out 
that with an ordinary magic lantern, and a quarter- plate, or carte-de-visite 
lens, the photographer has a most efiicient enlarging apparatus, which, with 
a very thin fully developed transparency, and a lamp and reflector so arranged 
as to equalise the illumination over the entire field, clean lenses, and suitable 
arrangements in the way of a screen upon which to place the sensitised 
paper, gives capital results. We have seen some excellent enlargements 
thus produced. 
A Suggestion for the Treatment of Old Nitrate Baths. — xAt the February 
meeting of the London Photographic Society, Mr. Johnson stated that, 
acting upon a hint given by Mr. W. Morgan Brown, he had tried the action 
of permanganate of potash upon old nitrate baths. He found that the salt 
became deoxidised, so that after filtration a perfectly colourless solution re- 
mained, giving clean pictures entirely free from fog. 
Neiu Apparatus. — Mr. Ernest Edwards, of Baker Street, and Mr. Johnson, 
have each introduced a new portable and very complete pocket apparatus for 
photographs 2 inches square. The lenses are Boss’s. 
Effects of Light on Glass. — Photographers have recently given considerable 
attention to the discolouration of glass bj'- light, a matter of great importance 
in connection with glass operating rooms ; and a paper by Mr. Thomas Gaffield, 
published in the American Journal of Science and Art, was made the subject 
of discussion at the February meeting of the North London Photographic 
Society. Mr. Gaflield describes experiments extending over four years, con- 
ducted with varieties of glass obtained from France, Belgium, Germany, 
America, and England. They demonstrate very clearly the degrees of in- 
fluence which sunlight has on the specimens experimented with. White 
French plate, and all white sheet glass of the better kind changed to a yellow 
hue after a month’s exposure to strong sunlight, but the dark green, dark 
blue, and bluish green remained unchanged. Window glass ranging from 
the white of French plate to the green of English sheet glass, gave the 
same results, but the dark green, blue, and blue-green remain unchanged. 
A brownish green sample made in Belgium, also remained unchanged. 
Every specimen of plate glass tested, except an inferior blue kind, and a 
