S82 Miscellaneom Intelligence. 



It is evident, tliat, to produce by a machine a current of electricity 

 equal to that produced by a pair of plates, the machine must be 

 competent to produce the same difference of electric tension between 

 two metallic plates, in communication with each other by a stratum 

 of acidulated water, not thicker than that interposed between the 

 two plates which form the voltaic point ; but far from observing an 

 effect to this extent, no application of electrical machines has been 

 able to produce an appreciable difference. 



" I may observe," says M. Ampere, " that for the observation of 

 a difference of electric tension between two bodies, by the electro- 

 meter, it is necessary that the cause which makes the electricities 

 of different kinds pass into the different bodies, should be able also 

 to maintain those bodies in the electric states produced; and pre- 

 vent the reunion of the electricities, at least for the time requisite 

 to put the electrometer leaf in motion. This circumstance takes 

 place in contact, but not in the union of two bodies; in accordance 

 with the explanation contained in my memoir of Dec. 3, 1823. 

 The combination of two particles can only produce an instantaneous 

 current; and the effects on the galvanometer are observed, because, 

 successive particles combining produce a succession of effects. But 

 in this case no sensible tension should be produced capable of being 

 exhibited by the electrometer, because nothing opposes the union of 

 the two electricities in the liquid where they have been produced ; 

 and it is only a portion of these two electric fluids, which, uniting 

 by means of the wire of the galvanometer, produce the effect on 

 the magnetic needle. In accordance with this view, M. Becquerel 

 has observed that the electricity produced by the combination of 

 an acid and an alkali, does not act on the electrometer when the 

 metallic wire which unites these two substances is interrupted, 

 though the current is found by the galvanometer to exist when the 

 wire is continuous. — Ann. de Chim. xxvii. 29, 



2. Electromotive Action of Water on Metals.— M. Becquerel has 

 endeavoured to ascertain experimentally the electrical effects pro- 

 duced by the contact of water and metals. The effect is so small 

 as to be easily mistaken for, or confounded with, those due to elec- 

 tricity produced accidentally during the performance of the experi- 

 ments, by contact of various parts of the apparatus, or in other 

 ways : but taking every possible precaution, and testing his results 

 in all ways, he arrived at the conclusion that zinc, iron, lead, tin, 

 copper, §-c. communicated positive electricity to water ; whilst pla- 

 tina, gold, silver, SfC. gave it negative electricity. Water is therefore 

 positive with the metals which are most positive, and negative with 

 those which are least positive. It behaves, therefore, witii oxidable 

 metals as alkalies do in their contact with acids, when there is no 

 chemical action. The same phenomena take place even when a 



