POLYORAMA—DISSOLVING VIEWS—DIORAMA.
THE description of the polyorama naturally follows that of the
phantasmagoria, being a practical application of precisely the same
principles. In the case of the polyorama, however, two or even more
lanterns of the best construction, are used. There are therefore two
sets of lenses identical in every particular, placed side by side, in
the same line, the foci of both being adjusted for the same spot, so
that the images refracted from each may superpose each other without
difficulty. In each instrument there are the same pictures, but they
differ in certain particulars, as we shall see presently.
In the phantascopes shown in figs. 52 and 54 there are two sets of
lenses; the first carries a glass bearing the image of a skeleton in a
winding sheet, while on the glass belonging to the second a naked
skeleton is portrayed. If, therefore, at a given instant the first
lantern is shut off, the spectators see the winding sheet torn, as it
were, suddenly from the spectre before them. The first lantern being
turned on once more, the skeleton is instantly reclothed in its hideous
garb.
It is of course not necessary always to choose such horrible subjects
for representation, as it is possible to produce changes of a much more
agreeable nature. For instance, a volcano may be depicted during its
tranquillity, with the sun shining on its verdant sides, and surmounted
with a gently rising wreath of smoke. Then it may be shown at night,
with its crater vomiting flames and red-hot stones, while streams of
lava are flowing beneath. By proper mechanism, one lantern may be
gradually shut and the other as gradually opened, producing an effect
that appears perfectly natural, from the gentle change which takes
place. Daylight, twilight, and moonlight effects may be easily made to
succeed each other in their proper order, and the most opposite scenes
may be made to change each other by proper appliances. Those who have
seen the dissolving views at the Polytechnic, know what effects are
produced by this very simple means. A virgin forest changes to a crowded
church, which in turn dissolves into a scene on the Alps.
The diorama, properly so called, invented by the illustrious Daguerre,
differs completely in principle from the apparatus we have just been
describing. As its etymology indicates, the pictures shown are seen
_through_. As in the case of the polyorama, there are two different
effects painted upon the cloth, which are brought out by a double system
of illumination.
[Illustration:
FIG. 66.—Diorama.
]
Fig. 66 will show the way in which these changes are managed. The large
picture, which is hanging vertically, is painted both in front and
behind. The front is illuminated by reflection from a semi-transparent
screen placed over it, which receives the light of the floor above. The
back is lighted from the windows behind, which are provided with blinds
to regulate the amount of light. The effects produced by the diorama
were truly marvellous, and Daguerre had a special talent for this kind
of painting. His famous _Midnight Mass_, which was exhibited at the
Regent’s Park, was one of the most renowned of his works. The scene
first represented a dark, empty church, feebly lighted by a small altar
lamp, but gradually the lights appeared here and there, worshippers
congregated in front of the altar, filling the nave and aisles. In Paris
the same scene was exhibited, representing the interior of the Church of
St. Germain l’Auxerrois with such perfect reality, that a countryman
actually threw a halfpenny against the painted canvas, to see whether he
were really in a church or not.
The next scene represented the destruction of the village of Goldau,
near Lucerne, by a landslip. First there appeared a smiling fertile
valley, its sides crowned with verdure; a storm gradually rose, the rain
fell, the wind blew, the lightnings flashed, and the thunder rolled in
the distance. Darkness at last closed in, and when the sun once more
rose over the valley, nothing was to be seen but a mass of fallen rocks.
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