Conductors of Electricity, and during Electrolysis. 271 



metically sealed into the ends of two pieces of glass tubing : 

 within these tubes, pieces of copper wire were metallically 

 connected with the platinum ; these, when the apparatus was 

 in action, terminated in mercury cups. The tubes thus pre- 

 pared were bound together by thread, so as to keep the pieces 

 of platinum foil at the constant distance of half an inch asun- 

 der. This apparatus was immersed in two pounds of dilute 

 sulphuric acid, sp. gr. 1154, contained in one of thejars (22.). 



49. A battery of twenty-four inch, double iron-zinc plates, 

 was then placed, with its divided troughs (which were charged 

 with a pretty strong solution of sulphuric acid), at a distance 

 from the galvanometer sufficiently great to obviate any dis- 

 turbing effect on the needle. To the electrodes of this battery 

 thick copper wires were secured, so that by means of one of 

 them connexion could be made to the galvanometer, and by 

 means of the other, to the decomposing cell. In fig. 4, A 



Fig. 4. 



represents the battery, G the galvanometer, and E the de- 

 composing apparatus (48.). 



50. In order to ascertain the resistances of the battery or 

 of the cell, I provided several coils* of silked copper wire, 

 the resistances of which had been determined by careful ex- 

 periments. When these were traversed by the current, they 

 were placed in such a position as to prevent any action on 

 the needle, and at the same time they were kept under water, 

 in order to prevent them from becoming hot, which would 

 have had the effect of increasing their resistances. 



51. When everything was duly prepared, the battery was 

 placed in its troughs, and the current from it was urged 

 through the galvanometer and each of three of the coils, 

 which were placed in succession at E (the decomposing ap- 

 paratus having been removed). The resistances of these coils 

 were 4*4, 5'5, and 7'7, and the currents which they allowed 

 to pass were 1°'88 Q, 1°'65 Q, and l°-29 Q. 



52. The decomposing apparatus was now replaced, and the 

 proper connexions being made, electrolytic decomposition 



* Two of these coils had heen previously employed (31. 41.), &c. in 

 ascertaining the resistances of the voltaic pairs : the resistance 0*06 was 

 that of the galvanometer and connecting wires. 



