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76 MODERN MAGIC LANTERNS.
diversity in this respect, but it is now getting customary for
slides to be marked on the lines laid down by the Photographic
Club a few years ago, this should always be done. The
marking consists in indicating the two top corners of the
slide by two spots, which are best white on a black background,
or black on a white one, as shown in Fig. 43. Not
only must they indicate the top of the slide, but they must
act as a guide to the face of the slide, which has to go next
the condenser. To ascertain this, the slide should be held
up in front of a piece of white paper in the position in which
it is intended to be seen upon the screen, that is to say, with
any inscription it may contain reading the right way round
and not backwards. The two spots, which may conveniently
be cut out of stamp-paper with a punch or pair of scissors,
should then be stuck on the two top corners of that side of
the slide facing the observer. In putting slides into the
carrier, they must be put in upside down for reasons pointed
out before (chapter X.), and when to be seen by reflection on
an opaque screen of any kind (Fig. 54) the spotted side must
go next the condenser ; when shown on a translucent screen
(Fig. 56) the spotted side of the slide must be turned away
from the condenser. If this is not attended to, the picture
as seen will be reversed from left to right, and any lettering,
names over shop doors, and the like, will read backwards.
The slides should always be rubbed over with a clean
duster before being shown, any dust or finger marks upon
them will be enormously magnified on the screen. For this
reason they should be held by one corner on putting them
into the carrier and not fingered all over.
During an exhibition of slides the room should be kept as
dark as possible. This seems so obvious as not to require
mention, but the writer has often seen the brilliancy and
beauty of a display spoilt by the amount of stray light about
the room, proceeding both from the ordinary lights which
were only turned down and neither quite nor almost extinguished,
as they should have been, and from the back of
the lantern itself. Another cause of failure is to be found in
a rickety lantern-stand. We have a lively recollection of an
exhibition of slides in which the lantern-stand, though firm
enough in itself, was mounted on a platform of floor boards
THE MANIPULATION OF THE LANTERN.
insufficiently provided with supporting joists, in consequence
the exertions of the lanternist in putting a fresh slide into
the carrier were sufficient to make the picture on the screen
wobble up and down quite a foot. Minor matters are the
following :
Do not omit to turn the lime, from time to time.
Keep the audience away from the immediate neighbourhood
of the screen ; they will see better and like
it better, although as a rule they will not do it of
their own accord.
Make sure there is ample gas for the display, even if
accidentally prolonged a little.
Never allow the audience to see the bare screen
illuminated with the full light of the lantern, all slides
will look dull and heavy after so doing.
The gas, if in bags, should be kept where it cannot
be meddled with; if in cylinders, where they cannot
roll or fall.
Be particularly careful never to put a slide in
upside down or wrong way round, unless they are
those of a friend who is present and who neglects to
spot them.
Never leave a lime in the lantern after use. If done
with throw it away, do not let it fall to pieces and
fill the lantern with dust.
77