DESCRIPTION OF THE FIGURES. 



PLATE I. 



Fig. 1. The galvanic pile, as originally constructed by 

 Volta, where the letters C, Z, and F denote the plates of 

 copper and zinc, and the pieces of cloth or pasteboard soaked 

 in fluid. The pile has four rods placed round it, to keep it 

 in the perpendicular direction. The lower end was called the 

 copper and the upper the zinc end. 



Fig. 2. When the number of plates is very considerable, 

 Volta divides it into two or more parts, each being connected 

 by slips of metal. In this case, it is essential that the same 

 order of parts be observed from one end to the other, up the 

 first pile, down the second, up the third, and, lastly, down 

 the fourth. 



Fig. 3. This was a modification of the galvanic apparatus, 

 that was formed by Volta, which he called couronne des tasses, 

 where the zinc plates Z and copper plates C are not in con- 

 tact, but are connected by metallic rods, and then immersed 

 in a fluid. 



Fig. 4-. Represents the battery of Mr. Children, which is 

 a combination of the couronne des tasses of Volta and the 

 trough of Cruickshanks. The plates are not in contact, but 

 each pair is connected by slips of metal, and the whole is at- 

 tached to a beam, so as to be lifted out of the cells at plea- 

 sure. The trough and partitions may be formed of either 

 wood or earthenware, and contain the fluid that is to act on 

 the zinc plates. 



Fig. 5. Represents the trough apparatus invented by Mr. 

 Cruickshanks ; the plates of zinc and copper are soldered to- 

 gether, and are then cemented into a wooden frame, leaving 

 intervals between the double plates, to receive the fluid which 

 is intended to act upon the zinc. It is provided with wires at 

 each end, which are in opposite states of electricity, and may 

 be applied to any substance which it is proposed to subject 

 to its influence. 



Fig. 6. Represents the apparatus, which was employed by 

 Sir H. Davy to exhibit the decomposition of salts, and the 



