236 Scientific Intelligence. [March 



to resist the idea that the voltaic current which we have seen is de- 

 pendent upon oxidation, must be preceded by a state of tension in the 

 fluid, and between the fluid and the zinc, the first consequence of the 

 affinity of the zinc for the oxygen of the water. He endeavoured to 

 investigate this by transmitting a ray of polarized light through a 

 solution of sulphate of soda across the course of the electric current, 

 and examined it by an analyzing plate, but though it penetrated 

 seven inches, not the slightest trace of action on the ray could be de- 

 tected, nor was the effect different when nitrate of lead was substi- 

 tuted. A beautiful experiment proves a state of tension acquired by 

 the metals and the electrolyte before the electric current is produced, 

 and before the metals are brought in contact. He took a voltaic ap- 

 paratus consisting of a single pair of large plates, namely, a cylinder 

 of amalgamated zinc and a double cylinder of copper, and placed them 

 in ajar containing dilute sulphuric acid, so that they could at plea- 

 sure be placed in metallic communication by means of a copper 

 wire, arranged so as to deposit the ends into two vessels of mercury 

 connected with the two plates. As long as the plates were kept sepa- 

 rate no action occurred ; but when connected, a spark (contrary to 

 the common idea) was elicited, and the solution decomposed. Hence, 

 it appears that as the electricity is produced by the material action 

 of the zinc and water, so these by being brought in contact are placed 

 in a state of powerful tension, which, although it did not decompose 

 the water, caused a spark to pass between the zinc and a fit discharger 

 when the interval was small enough. The idea which Berzelius has 

 broached that the heat and light of combustion are the consequences 

 of the action of chemical affinity, without the production of an elec- 

 tric current, appears to the author to be a mere imagination. 



With regard to the direction of the movement of evolved and com- 

 bining bodies, it appears that if in a voltaic circuit, the activity of 

 which is determined by the attraction of zinc for the oxygen of water, 

 the zinc move from right to left, then any other cation included in 

 the circuit being part of an electrolyte will also move in the same 

 direction, and as the oxygen of the water by its natural affinity for 

 the zinc, moves from left to right, so any other body of the same class 

 with it I. e. any anion will follow the same course. 



These statements of our author correspond with the general views 

 of Davy in his Bakerian lecture. 



(To be continued.) 



Article VIII. 



SCIENTIFIC INTELLIGENCE. 



I. — Mellonis Experiments on Heat. 



Royal Institution Evening Lecture, 23rd of January. 



Dr. Faraday commenced the lectures of the season by describing 

 and exhibiting the experiments which Melloni, a young Italian 

 philosopher now resident at Paris, contrived to elucidate the nature 

 of heat. 



The great improvement which he has introduced, and which bids 



