348 Mr Kemp wi the Electro-Magnetic Properties, of Carbon. 



or not the passage of a very large quantity of electricity accele- 

 rates or retards the combustion of the charcoal ; or, whether the 

 electricity may not altogether deprive the charcoal of its affinity 

 for oxygen. 



Experiment. — Having prepared a cylindrical piece of char- 

 coal C (Fig. 7.), an eighth of an inch in diameter, and in- 

 serted its extremities into two cups A, B, which contained 

 mercury, so as to be in perfect contact with the mercury, 

 three galvanic troughs, each of sixty plates, four inches square, 

 were charged with a .jveak solution of muriatic acid and wa- 

 ter. They were placed parallel to each other, and their simi- 

 lar poles connected, so as to form one battery, equivalent to 

 one of sixty plates, seven inches square. The circuit was com- 

 pleted by a copper wire, of the same thickness as the charcoal 

 to be afterwards used. The wire affected the needle, when 

 brought over it at a distance of seven inches, very powerfully. 

 The wire was now cut through its centre, and its cut extremi- 

 ties placed into each of the cups of mercury, so as to form 

 through the charcoal the galvanic circuit. The needle, sus- 

 pended by means of a fine fibre of silk, was theii brought above 

 the charcoal as closely as possible, but without coming in con- 

 tact with it, yet not the shghtest effect was produced on it. 



Experiment. — The same troughs, without any more acid 

 being added, were now arranged, so as to form one battery of 

 180 plates, four inches square, and the circuit completed by a 

 wire brought over the needle. The effect upon it, of course, 

 was much less than with the former arrangement. The wire 

 was then cut, as formerly, and its extremities brought into con- 

 tact with the mercury in tjie cups, so as to form the galvanic 

 current through the charcoal. The needle used in last experi. 

 ment was now brought over the charcoal, and it was imme- 

 diately affected. 



As long as the circuit remained complete, a deviation of eight 

 or ten degrees only took place ; but when the circuit was alter- 

 nately broken and completed, by taking out and again dipping 

 the wire into the cup of mercury, and watching the instant 

 when the needle attained its maximum of deviation at the time, 

 it was made to stand almost at right angles to its natural posi- 

 tion. 



