Properties of Carbon when in Combustion. 347 



it tightly, having a narrow longitudinal opening cut in it, e f. 

 At each end of the opening, two small cavities, g gy were also 

 formed. Fig. 6. represents the surface of the cover. 



A wire from each end of the galvanic apparatus already de- 

 scribed, was made to terminate in each of the small cavities, ggy 

 into which a small portion of mercury had previously been 

 poured. 



A cyhndrical piece of charcoal, a quarter of an inch in dia- 

 meter, and six inches in length, being prepared from beech, and 

 well washed, a copper wire was coiled round each end of it, 

 leaving a space of four inches in the middle, without any metal- 

 lic communication. The wires were so formed, as that their extre- 

 mities might dip into the small cavities, g g^ to complete the 

 circuit, as seen in Fig. 5. 



The jar being now filled with oxygen gas, the needle was 

 placed on the pivot, and allowed to take its natural direction. 

 The longitudinal opening e J\ was also closed by a piece of 

 wood fitted into it, and removable at pleasure. 



Experiment. — The piece of charcoal having been heated to 

 redness in the flame of the blowpipe, was immediately passed 

 into the jar, through the longitudinal opening e Jy (the piece 

 of wood being removed and again replaced), and made to de- 

 scend, until it was about a quarter of an inch above the needle, 

 and parallel to it. The other extremities of the wires were 

 turned, so as to terminate in the cavities g g. 



The circuit being completed by means of wires brought from 

 the former apparatus, and terminated in the cavities g g, the 

 needle immediately deviated from its natural position, which 

 proved that the electricity not only passed along the charcoal, 

 but that the charcoal also became magnetic, like metallic wires 

 of the same thickness, when conducting galvanic electricity. 



From the small apparatus which was used for exciting the 

 galvanic energy in this experiment, and the consequent diffuse- 

 ness with which tlie electricity passed over the charcoal, it being 

 necessarily thicker than a metallic wire, to prevent it being bro- 

 ken, the effect produced on the needle was not very powerful. 

 If a large apparatus were used, such as that belonging to the- 

 London Institution, experiments of an extremely interesting na- 

 ture might be performed ; as, for instance, to ascertain whether 



