26 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



cisterns of each magnet, the ends of which dip into the 

 mercury contained in the troughs upon the stage ; and 

 through the sides of the trough wires are passed, entering 

 into the mercury contained in the troughs, and bearing at 

 their ends other cups to hold mercury. To steady the mo- 

 tion of the magnets, wire loops are affixed to them, which 

 embrace the upright pointed wires on which the magnets 

 rest. A hollow pillar is firmly affixed to the stage, in which 

 a bent wire supporting another cross wire is inserted, and is 

 capable of being raised or lowered, and secured at any re- 

 quired height by a binding screw. The two ends of the 

 cross wire are bent downwards and pointed, and made to 

 enter the two small cisterns affixed upon the magnet^. A 

 third cup to contain mercury is also provided at the top of 

 the cross wire, and a communication being made with the 

 battery by means of uniting wires dipping into the mercury 

 in the cups, the wire from the positive end of the battery 

 being placed in the upper cup, and the wire from the nega- 

 tive end in each of the lower cups, the magnets will begin 

 to rotate in opposite directions, and those directions may be 

 reversed by changing the situations of the uniting wires. 

 Two batteries should here be employed, in order to make 

 both the magnets revolve with the desired velocity ; and 

 attention must be paid, when using two batteries, that the 

 currents of electricity flow in the same direction ; otherwise, 

 the phenomena of the revolutions of the magnets in contrary 

 directions will not take place, but they will both revolve in 

 the same direction. Price, $9.00. 



Ampere's Rotating Battery. (Fig. 446, next page.) This 

 consists of a U formed magnet, supported on a mahogany 

 or brass base ; in the ends of each pole of the magnet there 

 is a small hole, with a well-finished centre, and in which 

 pointed wires are made to revolve, supporting a double 

 cylindrical copper vessel, having a bent metal wire fixed to 

 the top of its innermost cylinder, with a vertical wire pointed 

 at both ends fixed in the middle of that bent wire and hung 

 upon the upper end of each pole of the magnet, the lower 

 points of the vertical wires of each vessel, entering the 

 holes, formed as above described, in the magnet for that 

 purpose. Two hollow cylinders of zinc, each furnished with 

 similar bent wires, having holes made in the under sides of 



