471- The Rev. N. J. Callan on a iww Galvanic Bailer^. 



the zinc of each circle would contain 80 square feet; or as 3 

 circles, two of which would contain 56 square feet of zinc, and 

 the third of which would contain 48 square feet ; or as 4 circles, 

 in each of which there would be 40 square feet of zinc; or as 

 5, in each of which there would be 32 square feet of zinc ; 

 or as 6 circles, four of which would each contain 24 square 

 feet, and two of which would each contain 32 square feet of zinc ; 

 or as 10 circles, in each of which there would be 16 square 

 feet of zinc ; or as 20 circles, each of which would contain 8 

 square feet of zinc. 



The mercury troughs are made by cutting holes for con- 

 taining mercury in a piece of wood 3^ feet long, S\ inches 

 broad, and 2 inches thick. The mercury trough by which 

 all the zinc and copper plates are made to act as a single pair, 

 contains two parallel grooves, each nearly S\ feet long, | of an 

 inch wide, and an inch deep. One of the grooves receives 

 all the wires of the zinc plates, and the other receives all the 

 wires of the copper cells. Hence when mercury is poured 

 into the two grooves, all the zinc plates are in metallic commu- 

 nication with each other, and act as one plate ; and all the co})- 

 pers likewise act as one copper plate. This trough is repre- 

 sented in fig. 4. ; the letter z shows the groove for the wires of 



Fig. 4. 



the zinc plates, and c the groove for the wires of the copper 

 cells. In the second mercury trough there are four grooves, 

 each of which receives 10 wires. There is a communication be- 

 tween one of the grooves containing the wires of ten copper 

 cells, and that which receives the wires of the zinc plates im- 

 mersed in the remaining 10 cells. Fig. 5. represents this 



trough. The third trough contains 6 grooves ; the fourth, 8 ; 

 the fifth, 10; the sixth, 12; and the seventh and eighth each 

 contain 20. Except the trough by which the battery is made 

 to act as 20 voltaic circles, the rest are made like the trough 

 represented in fig. 5. When the battery acts as 20 cir- 

 cles, the wire of each zinc plate, and the wire of the next 



