Modern magic lanterns; a guide to the ... - Yesterday Image

THE MANIPULATION OF THE LANTEEN. 77case, the light is centred, and must then be adjusted asregards its distance from the condenser. This is done bysliding tray and all in the grooves of the lantern until thedisc is evenly and brightly illuminated all over (f) ; thecorrect position is easily found. The carrier should then beadjusted so that its opening occupies the centre of this disc,and if it can be clamped in that position when found, somuch the better. This being done, it is useful to put a slideonce more into the carrier, and with the rack and pinionmotion of the lens midway, i.e., neither fully in nor fullyout, to focus it with the sliding adjustment only. If this isnot done, it may be found that it is impossible to focuseach slide sharply with the rack and pinion because it is atthe end of its travel.The sUdes demand the next attention. If practicable itwill be found an excellent plan to tie them up in a paperparcel and put them in a warm oven for a short time. Ifthis cannot be done they may be warmed by being placedin an open grooved box before the fire, or even allowed toremain, separated, in a warm room for a httle while. Unlessthis is done, there will be a great likelihood in the intenseheat of the hmelight or electric light of the deposition ofmoisture on the cold slide when put into the lantern. Theslides when this is the case are said to "sweat," it is painfullyobvious on the screen, and will spoil completely anexhibition which is in all other respects first-class.The slides must be arranged in the order in which theyare required. For this purpose they are often kept ingrooved boxes, but this way may lead to mistakes. Themost careful lanternist may have his attention distractedfor a moment, and in the obscurity may take a slide fromany part of the box instead of the next in order, and so getthem disarranged and make one of those slight but annoyinghitches which mar what should be the regularity which leadsto success. For this reason we prefer to have the slidespiled up in stacks of about thirty, only one of which shall bewithin reach at a time, there is then no possibility that anysHde but the next in order can be picked up by accident.Another important detail is the proper marking of theslides. There has been for many years every possible