-New form of Lantern ( 



L cylinders of wood (a).* Wooden 

 VQ with gentle friction, bear a wire 

 ;vstera of needles is suspended by 

 upper needle is midway between 



this 



age of the lower needle V 



^{h)i 



the centers of the two coils. The lower needle 

 scale (s) photographed on glass, beneath which is t 

 condensing lens of the vertical lantern. The needles are ordi- 

 nary sewing needles, and are each 1-5 inches in length. f Each 

 coil is composed of 34 7 meters of wire, the resistance of which is 

 0-444 ohms. Each coil should have the same number of wind- 

 ings, and the same resistance. This is easily effected by care 

 in winding. By sliding the rods (b) in or out, the distance 

 between the coils may be varied from 2 cm. to 10 cm., the 

 ig in all cases perfectly distinct. In 

 Ijusted to currents of any strength, 

 ve to regulate the distances. 



On the outside of the box are 

 six plates of brass, whose form 

 and arrangement are shown in 

 , fig. 2. The extremities of the 

 coils are connected with the four 

 plates A, B, C, D. This con- 

 nection may be made by means 

 of binding-^screws on the inside 



Ti n n \tv ^^ *^^ ^o^' "^ ^^'^^°^^ ^^^^ ^'^^ 



""ifi / \ h^- "^ coils may be replaced with ease 



H^ S Ir bX rJC_ by others of greater or less re- 



sistance. The plates are put m 

 metallic contact by means of 



* For Duboscq's lantern, the coils must be placed lower than here represented. 





