Aug. 24, 1 888.] 



SCIENTIFIC NEWS. 



W 



PORTABLE MAGIC LANTERN. 



AVERY compact form of magic lantern is illustrated 

 in the cuts accompanying this article. It is 

 adapted for all experimental purposes, as well as for the 

 projection of views. The best way to give a correct 



Fig. i. 

 idea will be to take, as example, a 4^ inch condenser 

 lantern, and give the dimensions of the different parts, 

 as shown in the cut. The size of the condensers settles 

 the question of the measurements of the other parts. 



The two condenser lenses, plano-convex, are mounted 

 each in a separate board. A circle is turned out with a 

 rabbet in each board, in which the condenser seats itself, 



Fig. 2. 

 and is secured therein by three buttons. The rear con- 

 denser board, A, is 6| inches square. The front board, 

 B, is of the same width, but 8| inches long. To the 

 rear one a strip is screwed across the top edge, and the 

 front one is hinged to this strip. At their bases, coming 

 between them, two small abutting strips are secured. 

 The thickness of the strips is such that the boards, when 

 brought together, with the strips in contact, are strictly 

 parallel, and the lenses are held apart from each other. 



The frame or base of the lantern is a rectangle, 

 a little over 6% inches across, and 13 inches long 

 in internal measurement. It is closed at the front 

 and open at the back of the lantern. It is 2\ inches 

 deep; 7£ inches from its front, the back condenser 

 board is hinged to a strip that runs across the top of the 

 frame, and is screwed firmly thereto, flush with its upper 

 surface. A long brass hook,/, and staple is provided, 

 for holding the condensers in place when vertical. The 

 boards are held together, when desired, by another 

 shorter hook, c, with staple. The condensers are then 

 in place for horizontal projection. To arrange them for 

 vertical projection, the small hook, c, is unfastened, the 

 front condenser, B, is pushed up until the two are at an 

 angle of 90 , and a plane mirror is inserted, resting 



against the two bottom strips. The mirror should be 

 mounted on a thin board or on a brass plate, so as to 

 provide strength and protect its back. 



A mortise is cut in the front condenser 6% inches from 

 its top, I inch wide and 3^ inches long. A piece of 

 board, a, is cut to slide smoothly back and forward 

 through this mortise. For retaining the strip in any 

 desired place, a hand screw, e, is placed on the side of 

 the condenser board, which is notched at both its lower 

 corners. A strip of brass is attached to the side of this 

 strip for the screw to press against. 



The strip carries the slide carrier b and lens C. The 

 lens is attached to a board about 4 inches wide and sj 

 high, with a tenon projecting from its base. A mortise 

 is cut near the end of the sliding strip to receive this tenon. 



A second mortise or slot, 4-^ inches long and 2 inches 

 wide, is made in the strip a. The slide carrier, b, is a 

 board 6| inches high by 4! inches wide. To its base is 

 attached a piece of wood 3 inches square. This is ^ 



