368 Progress of European Science. [Aug. 



Lastly, M. NoBiLi starting from the fact, that an electric current is established 

 in a metallic bar unequally heated, concludes that, in the pile, the action of liquids 

 on metals develops electricity, because it develops heat, which is unequally com- 

 municated to the metals. 



The electricity of the pile then has been attributed to three causes, viz. to sim- 

 ple contact, to chemical action, and to heat. 



M. Becquerel, for the last ten years, has been engaged in a train of researches 

 which have greatly added to electro-chemical knowledge : it is he who has 

 proved, in an incontestible manner, the development of electricity in chemical 

 action, a fact of the highest importance ; he has proved besides that, if it be true, 

 as asserted by Davy, that an acid and a solid alkali, become, by contact and before 

 their mutual combination, the first electro-negative, the second electro-positive ; it 

 is not true, as the illustrious English philosopher has maintained, that at the moment 

 of combination their electricities neutralise each other, for his experiments prove 

 on the contrary, that a current of positive fluid then arises from the base to the acid. 

 He has shewn besides, that two liquids of different nature may assume different 

 states of electricity, and thus form the elements of a pile. 



These discoveries, the fruit of very delicate and ingenious experiments, natural- 

 ly led their author to study the pile, not so much in respect to a general theory, 

 as with a view to an experimental analysis, such as should determine with some 

 precision the causes that influence its charge. 



M. Becquerel, in the first chapter of a work submitted to the French academy, 

 treats of such of these causes as are due to chemical action ; and his experiments 

 are directed to submit one element of the pile, as much as possible, to the influ- 

 ence of a single cause productive of electricity. 



Speaking of the action of different liquids on one another, he gives a sufficient 

 number of experimental results, from which it appears that an acid conducts itself 

 with a saline solution with which it mixes, as it would with a salifiable base with 

 which it would combine, that is, it is positive towards it. It seems also, that phos- 

 phoric acid is positive, relative to the muriatic, nitric, and sulphuric acids- a fact 

 curious enough. 



M. Becquerel, in examining the electricity developed by the contactof metals, 

 and of those acids which attack them, or of metals and saline solutions, proves in 

 general, that in the action of an acid on a metal, particularly when this action is 

 not very strong, the greatest part of the electricity developed, proceeds not from the 

 action of the metal on the acid, but from the mutual action of the solution of salt 

 produced and the free acid. 



Copper, lead, bismuth, zinc, and iron plunged in their respective nitrates be- 

 come negative by the addition of a few drops of nitric acid ; while those metals 

 which decompose water, iron, zinc, and manganese, plunged in their respective 

 sulphates, become positive as soon as some drops of sulphuric acid are added. 



M. Becquerel then takes up the subject of the electric effects produced when 

 two metals, connected by means of the wire of the multiplier, are partly plunged 

 either in the same liquid or in different liquids communicating together. Intfiis 

 case it is generally the mutual action of the liquids, and not the action of either 

 liquid upon the metal, which produces the greatest electric effect. 



He observed also, that in a pile formed of copper and zinc, the maximum 

 electro-magnetic effect is obtained when the copper is plunged in nitrate of 

 copper, and the zinc, in sulphate of zinc ; because, if the copper and the zinc be- 

 come, one positive, the other negative,-the nitrate of copper by its contact with 

 the sulphate of zinc becomes positive, whilst the second becomes negative, conse- 

 quently the sum of electricity developed is then the greatest. 



