Magic lantern with a double lens

Magic lantern with double lens. Butcher & Sons Ltd. Biunial. Lens: adjustable rack system. It holds maximum 9 cm width plates. Lighting: gas lamp. Also known as biunial, it was a lantern for professional use with double lens and a double illumination system. With this instrument I was possible to achieve the projecting affect dissolving views. For example, two images of the same landscape, with one from the summer and the other one from the winter, are placed in the upper and lower parts respectively in front of two focal points of the lantern. By regulating the intensity of the two light points, lowering one and increasing the other, it was possible to gradually change the image on the screen, with the summer scene transforming into a winter scene. This type of lantern appeared in England after 1857, where instruments with three lens camera came to be built.