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The Optical Magio Lantern Journal and Photographic Enlarger. 35
turning the handleto whichever branch the light is required, the oxygen is supplied to the one, and cut off from the other, and to both lanterns when the lever is placed mid-way.
When the oxy-hydrogen light is used, the dissolving tap is of a more complicated order, for not only has the oxygen to be diverged, but the supply of housc-gas or hydrogen must also be under control. In the form shown at Fig. 19, which is the invention of Mr. Wood, there are two separate taps, the levers of which arc connected by a rod, so that both move in unison. The oxygen supply is admitted at A, and the
oe oe hydrogen at B. The tubes P i : a ii FAL D and E ieading to the lanZann terns in the tap cross
each other so that in the case of two lanterns standing side by side, both sets of oxygen and hydrogen \@ tubes will be immediately Fig Ae. * behind each lantern. The oxygen is conveyed at C and F, and the hydrogen at D and F, the alternation being cFected by the movement of the lever G. Asit is essential that a smal! flame be allowed to burn during the time the light is suppressed, a small jet of hydrogen is kept burning, so as to avoid re-lighting.. This supply is regulated by means of a by-pass, as is shown in the cut.
Fic. 20.
In the bi-unial lantern, a form which is now almost universally employed, one lantern is placed above the other, the dissolving tap may
be of the form shown at Fig. 20. This class of
tap is supplied with by-passes for both hydrogen and oxygen, by which a small supply of both gases is allowed to reach the limes to keep them hot.
A dissolving tap for use with three lantcrns is a much more complicated affair than the forcgoing, although the general principle is the same. Not only must it be capable of directing the gases to any one lantern, but also to two and even to three at once when desirable. There are inthis case sixsupply tubes to be under control, and it cach had a scparate tap to be turned on and of, the difficulty can be better understood than expressed ; but the ingenuity of lantern-makers and exhibitors has happily overcome all difficulties in this direction, as illustrated in the cut Fig. 21. Allthat it is necessary for the operator to do is
to manipulate the handles; the by-passes are adjusted by means of the small thumb-screws shown.
Another conjunction of taps to achieve the same result is by first setting a lever (Fig. 22),
and then turning a tap. Its mode of working will be understood by the following :—The supplies vof hydrogen and oxygen are attached to HB and OB respectively. Then O2 is connected