ELECTRO-MAGNETIC INSTRUMENTS. 



can be communicated by a multiplying wheel attached to 

 the pillar. The pulley carries a steel wire, pointed at its 

 extremities, and bent at such angles as lightly to drag over 

 the faces of the files in rotation. The wire is removable at 

 pleasure to admit of its adjustment or replacement. The 

 axis is connected by a wire with the other cup on the base, 

 which is connected with one of the terminals of a galvanic 

 series ; the other cup is also connected with the other termi- 

 nal, a powerful coil being interposed between the cup on 

 the base and the galvanic battery. On putting the apparatus 

 in action, contact is made and broken alternately at nearly 

 opposite diameters of the disc. The effect to the eye is a 

 continuous circle of radiant and splendid scintillations. 

 This is perhaps one of the most delicately beautiful of elec- 

 trical experiments. Price, $8.00. 



Lockeys Coil Machine, with Scin- f ' 459 



tillating Circle. (Fig. 459.) In 

 this cut we have a representation 

 of Lockey's electro-magnetic coil 

 machine, to which is attached an 

 apparatus for producing luminous 

 galvanic rings. The contact-break- 

 er is the curved spring C, which is 

 carried rapidly round by the mul- 

 tiplying wheel and handle, d, stri- 

 king in its course against the 

 notches in the interior of the me- 

 tallic circle, b. 



The diameter of the ring a b is 

 about five inches ; they may be 



made of different metals, and if corresponding springs be 

 used, there will be a different light for each. The rings are 

 secured in the circular rabbit of the square piece of wood A, 

 by small turn buttons ; one end of the primary coil is in com- 

 munication with the ring, the other is in binding screw, e, 

 where one of the battery wires is to be fixed ; the spring, c, 

 has metallic communication with the other pole of the bat- 

 tery by means of its metallic socket, to which a wire is sol- 

 dered and brought down to another connecting piece sym- 

 metrical with e, but not visible in the figure; a small portion 

 of this wire is seen at g ; /, /, are the usual connecting pieces 

 from which the shock is received. Price $12,00. 



VOL. II. 4 



