so On the Construction of a Voltaic Apparatus. 

 the number of the plates, and the striking distance will in- 

 crease ; for we see throughout, the intensity proportioned 

 to the number, and it probably may be carried to such ex- 

 tent, as even to pass through a thicker plate of air than the 

 common spark. The great similarity of the appearance of 

 the electric light of this battery in vacuo, and that of the 

 common machine, might also be urged as an additional 

 proof of the identity of their nature. 



The effect of this large combination on imperfect conduc- 

 tors, was, as may be supposed, very great ; but of the same 

 platina wire, of which the four-feet plates fused eighteen 

 inches, this battery melted but half an inch, though, had 

 the effect been in the ratio of their surfaces, it should have 

 fused nearly fourteen inches. 



The absolute effect of a Voltaic apparatus, therefore, 

 seems to be in the compound ratio of the number and size 

 of the plates: the intensity of the electricity being as the 

 former, the quantity given out as the latter; consequently 

 regard must be had, in its construction, to the purposes for 

 which it is designed. For experiments on perfect conduc- 

 tors, very large plates are to be preferred, a small number of 

 which will probably be sufficient; but where the resistance 

 ,^^i<bf imperfect conductors is to be overcome, the combination 

 ^' ^' must be great, but the size of the plates may be small ; but 

 if quantity and intensity be both required, then a large num- 

 ber of large plates will be necessary. For general purposes, 

 four inches square will be found to be the most convenient 



size. 



Of the two methods usually employed, that of having the 

 copper and zinc plates joined together only in one point, and 

 moveable, is much better than the old plan of soldering 

 them together, through the whole surface, and cementing 

 them into the troughs : as, by the new construction, the 

 apparatus can be "more easily cleaned and repaired, and a, 

 double quantity of surface is obtained. For the partitions 

 in the trouo-hs, glass seems the substance best adapted to se- 

 cure a perfect insulation ; but the best of all will be troughs 

 made entirely of Wedgwood's ware, — an idea, I believe, first 

 lugcested by Dr. Babington. 



V. On 



