M. Pouillet on the Electricity of Elastic Eluids. 51 



it is formed, and touching the lateral surface of the charcoal, 

 which is negative, the two contrary electricities recombine. 



To obtain more intense and rapid effects, we may take seve- 

 ral cyhnders of charcoal having the same height, and place 

 them on their end, and very near each other, upon a sufficiently 

 large plate of brass ; then, after having set on fire all the su- 

 perior bases, we have a large column of carbonic acid, which 

 ascends, and is received against another plate of brass raised 

 some inches, or even as much as a foot, and communicating 

 with the condenser. With this arrangement the experiment is 

 very quick, and in a few seconds we have a strong charge of 

 vitreous electricity in the disk which communicates with the 

 carbonic acid. On the contrary, when we would have the 

 electricity of charcoal, we join the condenser to the brass plate, 

 upon which all the burning cylinders are standing. It re- 

 quires a few seconds of time before the condenser takes abund- 

 antly the resinous electricity. When the combustion is fed 

 by a current of oxygen, the electricity disengages itself more 

 rapidly, and takes a much stronger tension. A single instant is 

 sufficient for the gold leaves of the condenser to reach the 

 highest degree of divergency. But, in every case, whether it 

 operates on little or on great surfaces of charcoal, — whether the 

 combustion is left to itself, — whether it is increased by a cur- 

 rent of air or a current of oxygen, more or less lively, — if we 

 would obtain signs of electricity always certain and identical, 

 the essential condition is to inflame only the horizontal surface 

 of the charcoal in such a manner that the carbonic acid forms 

 and ascends in a moment, and without having touched any 

 body before arriving at the brass plate where it ought to de- 

 posit its electricity. This condition is so decisive, that if 

 we direct, for example, a jet of oxygen against the side of 

 a cylinder of charcoal, which is standing upon the conden- 

 ser, and if we thus excite a very lively combustion, which 

 even forms a deep cavity, it is impossible, in spite of the exces- 

 sive rapidity of the combustion, to collect sensible quanti- 

 ties of electricity ; or rather the signs which are obtained are 

 sometimes positive and sometimes negative. 



After this, it is sufficient to know that Lavoisier and La 

 Place, Volta, and de Saussure, made these experiments in a 



