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8 MODERN MAGIC LANTERNS.
flame, the channels through which they pass being in a
direct line with the chimney ; the light given by this form
is very satisfactory.
The following directions for the use of oil lamps may be
taken, except where otherwise stated, as applying to all
patterns, and should receive careful attention if it is desired
to get the best result :
The selection of the oil should not be left to mere chance,
nor half a pint of the cheapest " paraffin " got at the nearest
oilshop on the evening when it is required. Many of
the oils in the market, although perfectly safe in household
lamps in which the reservoir is of porcelain or other
material which is a bad conductor of heat, are positively
dangerous in the optical lantern, where, from the very nature
of the instrument and the exigencies of construction, the
receptacle for the oil is bound to get, at any rate, warm.
The best crystal oil must be got from a reliable dealer. The
addition of a lump of camphor about the size of a walnut to
each pint of oil has been recommended as making the light
whiter, but we have never been able to detect any improvement
in illumination by this means, over that got by theuse of
the best " crystal " oil. The wicks should not be too long, and
of course not too short, a couple of inches longer than
necessary to reach to the bottom of the oil reservoir is
ample ; before use they should be thoroughly dried. When
dry, the wicks, if new, must be trimmed with a pair of
scissors and replaced in the lantern, the reservoir filled
nearly full, whether the lantern is wanted to burn for ten
minutes or two hours, and after the lapse of a minute or
two for the wicks to soak they should be lit and allowed to
burn for a quarter of an hour. A funnel should always be
used for filling, and the greatest care taken to avoid spilling
any of the oil about the lamp, as it is only by such precautions
that the unpleasant smell can be avoided. The
chimney is best kept off for the first minute, and put on
when the lamp is seen to be fairly alight.
When the new wicks have burnt for a short time, they
can be trimmed once more with a sharp pair of scissors, so
as to give a perfectly even flame ; this trimming can only be
roughly done before the edges have been charred by use.
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OIL LAMPS. 9
They should be trimmed each time before use, but only that
part which is quite burnt need be cut off.
When the lamp is lit, it should be turned up fully at once,
and for the first few minutes must be watched, and turned
down a little as the lantern warms and the flame begins to
smoke, until it is seen to be burning regularly and steadily. To
avoid smell as much as possible, the lamp is never to be
allowed either to smoke or to burn below its maximum, the
greatest height of flame short of actual smoking being always
in use ; this will entail more or less constant attention,
but will obviate annoyance to the noses of the audience.
Another point which must be seen to, is that each of the
wicks is doing its fair share of the work. With two-wick
lamps this is the case when each is burning so high that
any increase in the height of the flame of either will cause a
smoke. With lamps possessing three or more wicks, the
inner wick or wicks should be in this condition ; the outer
ones are best a trifle lower.
When the chimney is adjustable in height, the lamp
should be removed from the lantern and the height of
chimney at which the light is at its best ascertained by experiment;
when found, the point should be marked on the
chimney once for all. If, now, when he lamp is replaced in
the lantern, the height requires altering to get the best
result, it indicates that the air inlets are not sufficiently free.
This is not often the case ; in fact, as a general rule, the
inlets for the air receive more attention from the makers
than the outlet at the chimney, which is sometimes so contracted
as to counteract the advantages gained by improved
inlets ; still, in good lamps, both matters are the subject of
careful study and experiment.
After a display, the lamp should be emptied of oil, the
wicks taken out, squeezed up in paper to free them from oil,
and put away until wanted again, and the metal parts of the
lamp washed with washing soda and warm water and dried.
If a little trouble in this way is taken with a petroleum
lamp, it can be used with almost an entire freedom from
smell, and the results will astonish those whose experience
of the oil lamp is gleaned from the greasy, messy abominations
which, with a little inattention, they readily become.