Set of painted glass slides

25.2 x 16 x 61.5 (case)
10.5 x 42.6 (slides)
Painted glass, wood and brass

INDEX 1788 : Z.II.390

Theca cum 36 laminis vitreis, corona lignea cinctis, plurimis figuris diversimode pictis.

Case with 36 glass slides, surrounded by a wooden wreath with a variety of differently painted figures.

In 1788 the Gabinete de Física had a set of three magnificent magic lanterns, two of which still appeared in the 1878 inventories. Unfortunately, none of them has survived to the present day. However, the Gabinete de Física still owns an excellent collection of painted glass slides, mounted in wooden frames, which were used to be projected through that type of lanterns.

There are images of men and women in typical dress of the times, kings and queens, courtiers, knights, monks, popular figures, strolling musicians, soldiers drilling, battle scenes, masked figures, buildings, sedan chairs, coaches, etc.

There is also a second case of slides some of which have moving parts, lending them a degree of animation. This is achieved by a shuttle movement of one slide over another, fixed, one. Their age and features make them excellent representatives of the history of animated graphics.

's Gravesande, in the Physices Elementa, gives us a detailed information about the construction and operation of the lanterns used to project the slides. These lanterns comprised a box topped by a chimney to allow fumes produced by a burning oil lamp inside to escape. The light from the lamp was cast on to a convergent lens placed at an opening in one of the lantern's walls, and set in a circular tube. The emerging light then fell on the painted figure on the glass slide, placed next to the lens on a fitting that formed part of the lantern. Another tube, which could be moved inside the first one, contained a second set of convergent lenses and a light beam collimator. The image was focused on a screen by moving this second set of lenses relative to the glass slide. Inside the box, on the opposite side of the lamp to the lens, was a concave mirror which reflected the light, intensifying the beam falling on the figure to be projected.

The 18th century "megalographic lanterns" in Coimbra would not be exactly the same as the one depicted by 's Gravesande, since dalla Bella referred in the Index Instrumentorum to a work by Christianus Wolff which would have been used as a model for the building of the Gabinete's lanterns.

's Gravesande, Willem Jacob, Physices Elementa, Leiden, 1742, Vol. II, § 3432, Tab. CIX.

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