1826.] Scientific Notices — Miscellaneous. 75 



from one state to another undergo a change in their electric 

 condition ; and he supposed that the electricity lost in storms 

 was continually being renewed by that produced by evaporation 

 perpetually going on from the surface, as well of the land as of 

 the water. 



The recent and interesting researches of Pouillet were in- 

 stituted not merely to ascertain the truth of the Italian pro- 

 fessor's hypothesis, he was also desirous of discovering the 

 efficiency of another cause, which he believed to be of no small 

 importance in the production of electricity, and of bringing to 

 proof a theory of his own relative to the distribution and accu- 

 mulation of this principle in the atmosphere. 



Numerous and varied experiments have brought him to the 

 conclusion, that the mere passage of a body from the solid 

 form to a state of vapour is unaccompanied by the develop- 

 ment of electricity; that the result is similar when vapour is 

 condensed either into the liquid or solid form. 



He conceived that Volta, though too accurate an observer to 

 be mistaken as to the fact of the presence of electricity in his 

 experiments, was, nevertheless, deceived, as to the cause of 

 its production, by the formation of carbonic acid, which mixed 

 with the vapour of water and complicated his experiments. 



In 1782 Volta, Lavoisier, and Laplace showed that elec- 

 tricity was developed during chemical action ; but as experi- 

 ments relating to this point are liable to afford different and 

 contradictory results from slight differences of circumstances, 

 the question has been regarded as rather undecided. It be- 

 came, on this account, an object of special attention with M. 

 Pouillet. He finds, that in the combustion of charcoal there 

 is an unequivocal production of electricity — that the acid 

 produced is in the positive state, while the charcoal always 

 becomes negative. It is necessary, in order uniformly to obtain 

 the same results, that the combustion should take place only at 

 the upper part of the piece of charcoal, and by no means extend 

 over the whole of it; otherwise the contact both of the 

 charcoal and of the carbonic acid with the plate of metal 

 destined to receive the electricity will render the experiment 

 irregular. To discover whether the electricity rendered 

 evident in the preceding experiment was to be attributed to 

 chemical action, or to the conversion of the charcoal from the 

 solid to the gaseous state, he examined the ffame produced 

 by the combustion of hydrogen. The external part of the 

 flame constantly exhibits positive, and the interior negative 

 electricity, a transfer of electricity taking place between the 

 molecules which are combining, and those which are about to 

 do so. This fact is supported by a great number of experiments 

 on the combustion of phosphorus, sulphur, the metals, alcohol, 

 sether, fat substances, and vegetable matter. 



