NATURAL PHILOSOPHY. 159 



rolled and soldered so as to form a hollow cylinder resting on 

 3 points. This is set in a glass cylinder of the same height, 

 at the bottom of which are placed some broken crystals of sul- 

 phate of copper, through which the 3 vertical points are forced, 

 the 3 bent horizontally resting on the sulphate. On well-fitting 

 discs of bibulous paper, passed over the copper cylinder down to 

 the sulphate, is placed a thin layer of sand. A zinc cylinder, 6 

 inches high, is then passed over the copper to rest upon the sand, 

 and then the space between the copper and the zinc and the zinc 

 and the glass is filled up with sand nearly to the top. The copper 

 C}'linder is then filled with powdered sulphate, and the battery is 

 set in action by pouring water upon the sand. According to him, 

 a battery of this size and description will keep in constant action 

 for more than two years. It is specially applicable to electric 

 clocks and bells. 



TOPLER'S ELECTRICAL MACHINE. 



This consists essentially of a circular plate or disc of vulcanized 

 rubber, gutta percha, or glass, mounted upon a vertical axis, and 

 caused to rotate rapidly by means of a band and wheel. The 

 disc is coated upon each side with two segments of tin foil, a free 

 space being left between the segments, while the coatings are 

 connected over the edge of the disc by strips of foil. A piece of 

 hard rubber, forming a segment of a circle, is then excited by 

 friction, and placed near and parallel to the lower coated surfaces 

 of the revolving disc. This lower surface becomes electrical by 

 induction, the opposite electricity being driven over the edge to 

 the upper surface of the plate. As the plate revolves, one under 

 segment of tin foil is removed from the inductive action of the 

 excited surface, and the second becomes parallel to it, when the 

 free electricity is decomposed as before. Two isolated conductors 

 are placed above and parallel to the disc, and each carries at one 

 end a light spring or strip of tin foil, which rests upon the upper 

 surface of the disc. The two strips are so arranged that, as the 

 disc revolves, one is just leaving a segment of tin foil as the other 

 is brought into contact with it. In this manner the electricity 

 driven to the upper surface is first carried off by one conductor, 

 while the electricity retained upon the lower surface at first, as the 

 plate revolves, passes to the upper surface, and is drawn off by 

 the second conductor. The same process then takes place with 

 the second coatin'g, and so on alternately. It will be seen that so 

 far the apparatus is exactly equivalent to an electrophorus, and 

 that the action, though powerful at first, must diminish rapidly as 

 the inductor loses electricity. To remedy this difficulty, a second 

 but smaller glass disc is placed on the same axis, coated with tin 

 foil in the same manner, and provided with a similar inductor and 

 similar conductors. This second inductor is connected with one 

 pole or conductor of the upper and larger plate. Of the two sim- 

 ilar conductors belonging to the lower plate, one is connected with 

 the earth, while the other is connected with the inductor of the 

 upper plate. In this manner, as the discs rotate, the earth fur- 



