The Art of projection and complete magic lantern ... - Yesterday Image

54of old tubing (shown tinted in drawing) and if a Y piece is not to hand tocarry the supply to the lantern from two burners, tie a knot in the oddpiece, leaving one open for the supply tube. It is always best to use aT or Y piece, it gives a much better supply. Be sure and remove theburner first before putting on tubing which supplies the lantern.Fig. 31-CONDENSERS.The object of a lens which is termed a condenser, is to take up aswide an angle of light as possible from the illuminant, be it oil, or limelight,and so cone it down in such a manner, as to pass it through theobjective, or front lens, which it does by refraction, wider the refractiveangle, shorter the focus, and consequently the shorter the focus ofcondenser, greater the light on the screen. This can be done with asingle condenser, only that the lens would require to be of such athickness, that much light is lost by absorbtion, and the chromatic andspherical aberration would also be very great, the disc appearing unevenwith a fringe of colour around the edge. The use of two lenses ofmoderate thickness accomplishes the desired result, and minimizesthe aberration.Condensers have been made in various forms and curvatures fromsingle bull's-eye, to the present triplet.Previous to the introduction of photographs, when slides were entirelypainted by hand, it was the rule to have the slides from six to eightinches in diameter, for the obvious reason, that more detail could bel)ainted in an eight inch circle than in a three inch picture. With thesethe