This is effected by having two slides painted, one with the tempest as
approaching on one side, and continuing in intensity till it reaches
the other. Another slide has ships painted on it, and while the lantern
is in use, that containing the ships is dexterously drawn before the
other, and represents _ships in the storm_.
The effects of sunrise, moonlight, starlight, etc., may be imitated
also, by means of double slides, and figures may be introduced
sometimes of _fearful_ proportions.
Heads may be made to nod, faces to laugh; eyes may be made to roll,
teeth to gnash; crocodiles may be made to swallow tigers; combats may
be represented; but one of the most instructive uses of the slides is
to make them illustrative of astronomy, and to show the rotation of
the seasons, the cause of eclipses, the mountains in the moon, spots
on the sun, and the various motions of the planetary bodies, and their
satellites.