At this moment a cord was pulled so as to
raise the camera, and then a few moments were allowed to elapse in
order that the apparatus might become immovable. As the objective was
all the time in the dark, it had neither cap nor shutter, but was
unmasked from the beginning of the operation.
In order to form an impression on the plate, it was only necessary to
give light; this being easily done by passing an electric current by
means of a commutator, so as to light the incandescent lamps. At the
end of the exposure, the lamps were extinguished and the entire
apparatus was immersed in darkness. The mean time of exposure was from
four to five minutes. The apparatus was then hauled up, and the
negative developed.
The experiments could be renewed as often as necessary, and the
apparatus be pointed in all directions by turning it a certain number
of degrees by means of a lever attached to the upper rod. In this way
were obtained various views of the inaccessible gallery in different
planes.
[Illustration: FIGS. 2 AND 3.--REPRODUCTION OF PHOTOGRAPHS TAKEN IN
THE INACCESSIBLE GALLERIES.]
We reproduce herewith two of Mr. Langlois' most interesting
photographs. One of these shows the head of the corpse of a young
miner whose face stands out in relief against the side of the gallery
(Fig.
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