Wohlgemuth, Adolf, b. 1868 · Cambridge, University Press · leaf 98
With this method, the lantern is fitted with a condenser consisting of two lenses, one (a) of which remains perpendicular in front of the source of light, whilst the other (6) can be lifted into a horizontal position and kept there by a mirror (c) forming an angle of 45° with each condenser-lens… … Fig. 11. Demonstration Lantern arranged for Expt. 28 projection-lens {d) is vertically above this arrangement and is fitted with a reflecting prism (e) which turns the rays again into a horizontal position on to a screen. The slide to be projected on to the screen is simply laid on the horizontal…
