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



less liable to oxydizement. A metallic communication is 

 made between the coating of the pivots and the galvanic 

 series within. In order to produce a connexion between 

 one recipient of this description, and another, it is only 

 necessary to allow a pivot of each trough to revolve on one 

 of the two ends of a strap of sheet copper. To connect 

 with the termination of the series or poles, the conductors, 

 one end of each is soldered to a piece of sheet copper, 

 which are placed under the pivots, to be connected with the 

 termination of the series ; to the conductors are usually at- 

 tached small hand-vices for conveniently introducing wires, 

 charcoal points, etc. ; the plates are usually about seven 

 inches long, and four wide. A battery of 300 pairs may 

 be contained in two troughs of six feet each in length, which 

 is capable of producing brilliant experiments. The liquid 

 employed in the cells is a mixture of sulphuric or muriatic 

 acid, with water in the proportion of one part of the former 

 to fifteen or twenty of the latter. 



In the figure two troughs are connected in one frame, and 

 both moved by levers terminating in one handle at the end 

 of the frame. This instrument is also superseded by the 

 more modern instruments. Price, 100 pairs, $80.00. 



Dr. Hare's Calorimotor (Fig. 38*7, next page) in which 

 a great quantity of heat accompanied by little electrical 

 tension is produced, consists of such an arrangement of the 

 elements as to form in fact but one, or at most, two pairs of 

 separate plates ; for all the zinc plates in one half of the 

 apparatus being connected together, constitute but one plate, 

 while all the copper ones being united afford another. The 

 plates are, however, arranged in an alternating series, so 

 as to present their surfaces to each other without occupying 

 much space. 



The accompanying figures represent the arrangement of 

 r&rts in the calorimotor. A and a are the cubical boxes 

 containing the one acidulated and the other pure water; 

 b b b b is the wooden frame containing the zinc and copper 

 plates alternating with each other, and from and |- an inch 

 apart ; T T t t, are masses of tin cast over the protruding 

 edges of the sheets which are to communicate with each 

 other. The smaller figure, representing a horizontal section 

 through the plates, shows the manner in which the junction 



