50 M. Pouillet cm the Electricity of Elastic Fhiids, 



the carbonic acid, the surest method to obtain regular and 

 constant effects will be, to isolate these electricities at the mo- 

 ment of their formation ; and, in order to do that, we must se- 

 parate as much as possible the burning body from the com- 

 bustible body. 



In arranging the experiment acccording to this plan, all the 

 contradictions disappear ; we can at pleasure collect the elec- 

 tricity of the charcoal or that of the carbonic acid, and thus 

 the phenomena are seen perfectly similar and with great inten- 

 sity. After many trials, I fixed upon the following arrange- 

 ment : To obtain the electricity of the carbonic acid, it is suffi- 

 cient to take a single piece of charcoal, of a sufficient diameter 

 to give it the form of a cylinder w^hose bases are nearly plain, 

 and to place it vertically six or eight centimetres below a 

 plate of brass, which rests upon one of the disks of the conden- 

 ser ; then, if the charcoal communicates with the ground, and 

 is lighted at its superior base without the fire reaching the late- 

 ral surface, there rises a column of carbonic acid which strikes 

 the plate of brass, and in a few seconds the condenser is charg- 

 ed. The electricity which it receives from the carbonic acid 

 is always positive. If, instead of holding the charcoal quite 

 upright, we give it nearly a horizontal direction, so that the 

 carbonic acid which is formed can only rise by ascending along 

 the base of the charcoal, which is thus vertical, no sensible 

 effect is obtained. In the same way, if, while holding it verti- 

 cally, we light the lateral surface as well as the superior sur- 

 face, an uncertain result is observed. 



To obtain the electricity which the charcoal itself takes by 

 combustion, we must place it by its inferior end directly upon 

 the disk of the condenser ; then, upon lighting its superior base, 

 the fire is sustained by a gentle current of air, and in a few 

 minutes the condenser is charged. The electricity which it 

 receives from charcoal is always negative. If the charcoal 

 touches the condenser only in some points, or if it burns on all 

 its surface, no effect is obtained. Without doubt, in the first 

 case, a small number of points of contact gives passage only to 

 too small a quantity of electricity, and, in the second place, the 

 carbonic acid being electrified positively at the instant when 



