184 Dr. Hare on a neiv Theory of Galvanism, 8fC. [Sept. 



hydrogen, which gives so much splendour to the experiment, 

 can only be exhibited advantageously on a large scale. 



Explanation of the Plate. 



A a, fig. 1, two cubical vessels, 20 inches square, inside; 

 h bb b, a frame of wood containing 20 sheets of copper and 20 

 sheets of zinc, alternating with each other, and about half an inch 

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

 the sheets which are to communicate with each other. 



Fig. 2, represents the mode in which the junction between the 

 various sheets and tin masses is effected. Between the letters 

 z z, the zinc only is in contact with the tin masses. Between c c, 

 the copper alone touches. It may be observed, that at the back 

 of the frame, 10 sheets of copper between c c and 10 sheets of 

 zinc between z z are made, to communicate by a common mass of 

 tin, extending the whole length of the frame, between T T ; but 

 in front, as in fig. 1, there is an interstice between the mass of 

 tin connecting the 10 copper sheets and that connecting the 10 

 zinc sheets. The screw forceps, appertaining to each of the tin 

 masses, may be seen on either side of the interstice ; and like- 

 wise a wire for ignition held between them. The application of 

 the rope, pulley, and weights, is obvious. The swivel at S 

 permits the frame to be swung round and lowered into water in 

 the vessel a, to wash off the acid, which, after immersion in the 

 other vessel, might continue to act on the sheets, encrusting 

 them with Oxide. Between p p there is a wooden partition 

 which is not necessary, though it may be beneficial. 



Fig. 3, represents an apparatus alluded to, p. 181. It consists 

 of a couronne des tasses, reduced to a form no less compact than 

 that of the trough ; hollow parallelopipeds of glass are substituted 

 for tumblers or cells. The plates are suspended to bars counter- 

 poised like window sashes. 



The advantages are as follows. The material is one of the 

 best non-conductors, is easily cleansed, and is the most imper^ 

 vious to solvents. The fracture of one of the cups is easily 

 remedied by a supernumerary. They may be procured (as in 

 the United States) where porcelain cannot be had. The shock 

 from 300 pairs is such as few will take a second time, some of 

 the effects have already been stated.. 



