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POPULAR SCIENCE REVIEW. 
work, c c c, made with the additional top-piece D, has only E, and by merely 
slipping the two brass rods at c c, and screwing it down by the thumb-screws, 
a, it becomes air-tight, without weakening the sides, c c. 
New Lens for Carte Portraits. — Mr. Davies, of Edinbm’gh, an amateur 
photographer and experimentalist of repute, for whose opinion we have 
extreme respect, speaks very highly of a new lens for carte portraiture recently 
introduced by M. Darlot, of Paris. It is of short focus and singularly wide 
aperture, and is said to be far more rapid in its action than any other lens 
of the kind made in this country. The stops are arranged very ingeniously 
by a novel system of levers, one taking the place of another with the greatest 
ease and readiness. 
The Oxyhydrogen Light . — At the May meeting of the South London Photo- 
graphic Society, Mr. Alfred Harman called attention to some improvements 
he had made in the retort in ordinary use for generating this light as used 
for photographic enlargements by the solar camera — a branch of the art in 
which he is attaining great repute. Using one of Jones’s retorts made of 
cast-iron, with a top fitting like that of a collodion bottle, to prevent an ex- 
plosion, he found a greater danger unprovided for in the rapidity with which 
the gas was generated (consequent upon the quantity of cast-iron contained 
in this retort), which is so great that very often the pipes are not large enough 
to convey it quickly enough to the bags, and the accident in question occurs, 
despite the top. The improved retort is shaped like a coffee-pot, and made 
of sheet iron, the pipes are larger, and at the top there is a safety-valve, 
which, if there should be a stoppage in the pipe, opens and allows the oxygen 
to escape. The smaller pipes in common use are frequently clogged by the 
manganese and chlorate mixture getting into them ; to avoid this danger, the 
pipe leading from the retort to the washing-bottle, is twice the size of that 
usually employed, and is also provided about midway with a hollow baU 
intended to receive any water that would otherwise pass into the retort, in 
cases when it becomes necessary to lower the temperature, and so check the 
too rapid generation of the gas. A second washing-bottle is used, because 
on trial the water in it was always found to be more or less impregnated 
with the manganese, which in its absence would pass into the bag, but the 
larger pipe is not used after the first washing-bottle is passed. 
