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2 MODERN MAGIC LANTERNS.
effected, the names of the various parts and their functions
had best be pointed out.
In Fig. 1, A represents the lantern body, generally provided
with a chimney, B. Inside this is placed a light, c,
in front of the light is a lens, known as a condenser, D, and
in front of the condenser again, and some little distance
from it, is another lens, called the objective, E. As close as
possible to the condenser and between it and the objective
is the slide, which is held between springs, in grooves, or in
some similar manner at F. The screen upon which the
pictures are thrown is shown at G. Here, then, are the
essentials of a magic lantern :
A light.
A condenser, l These are sometimes spoken of as "the
An objective, j optical system" of a lantern.
A carrier or slide-holder.
A lantern body, which encloses the light, and which
retains the various other parts in their relative
positions.
The means of illumination is a point of primary importance,
and it is due to the rapid strides in this particular
which have been made during recent years especially, that
the lantern has increased so largely in popularity. The
various lights now in general use are oil lamps, the
limelight, and the electric light, the illuminating power
of which is in the same ratio as the above order, oil
(and incandescent electric lamps under some circumstances)
having the least, the electric arc lamp the most, and the
modifications of the limelight occupying an intermediate
place in this respect.
In buying a lantern the choice of the light is one of the
first considerations. If it is intended for use for photographic
enlarging and for the exhibition of slides, etc., on
only a small scale, there are several forms of the oil lamp
burning petroleum which can be employed with advantage
in the direction of economy, both of trouble and money ;
especially if the user is likely to want the lantern where
house gas is not available and where there are difficulties in
the way of getting compressed gas. Where a considerable
size of picture is required, say anything over seven or eight
INTRODUCTORY. 3
feet in diameter, a more powerful light than that given by
a petroleum lamp becomes a necessity if a brilliant light
is wanted, and one of the forms of the limelight must
be used, or the still more powerful arc lamp. What
form of limelight, again, will depend to some extent
on the size of disc and illumination required. The " oxycalcium
" light and the " blow-through " or " safety " jet
can be used with success on discs up to twelve or fifteen
feet in diameter, but for anything over this size what is
known as the mixed jet should be employed. But these
sizes are in all cases the author's opinion only. Some
workers would be quite satisfied with less illumination than
that intended above, and would consequently use a less
Fig. 2. THE OPTICAL SYSTEM.
powerful light or a bigger disc ; others, on the other hand,
might wish for more illumination than he regards as
sufficient. It will be gathered froin the foregoing remarks
that the brilliancy of the picture depends upon the size at
which it is shown, and that, given the same light in each
case, the smaller the disc of light thrown upon the screen
the more brilliant it will be.
These two factors, the light and the size of the image,
are by no means, however, the only ones to be taken into
consideration. The function of the condenser is to collect
as much as possible of the light and direct it upon the slide ;
therefore, the more of the light that the condenser collects
the more brilliant will be the image. The objective is
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