202 



nometer, that, as no clieniical action took place, so no electric cur- 

 rent was produced ; yet the apparatus thus arranged could transmit 

 a very feeble thermo-electric current, excited by slightly raising the 

 temperature of the wires at either of their points of contact. Hence, 

 the inference may be drawn, that the contact of iron and platinum 

 is of itself productive of no electromotive force. On the other hand, 

 the author shows, that the interposition in the circuit of the smallest 

 quantity of an electrolyte, which acts chemically on either of the metals, 

 the arrangement remaining in all other respects the same, is imme- 

 diately attended with the circulation of an electrical current far more 

 powerful than the thermo-electric current above-mentioned. A great 

 number of combinations of other metals were successively tried in 

 various ways, and they uniformly gave the same results as that of 

 iron and platina. Similar experiments were then made with various 

 metallic compounds, and also with other chemical agents; and in all 

 cases the same general fact was observed ; namely, that when no 

 chemical action took place, no electrical current was excited ; thus 

 furnishing, in the opinion of the author, unanswerable arguments 

 against the truth of the theory of contact. The only way in which 

 it is possible to explain these phenomena on that theory, would be 

 by assuming, that the same law of compensation as to electro-motive 

 power is observed by the sulphuret of potassium, and the other fluids 

 of corresponding properties, as obtains in the case of the metals, al- 

 though that law does not apply to the generality of chemical agents ; 

 and in like manner, different assumptions must be made in order to 

 suit the result in each particular combination, and this without any 

 definite relation to the chemical character of the substances them- 

 selves ; assumptions, which no ingenuity could ever render consistent 

 with one another. At the conclusion of the paper, the author de- 

 scribes some remarkable alternations in the phenomena which occur, 

 when pieces of copper and silver, or two pieces of copper, or two of 

 silver, form a circle with the yellow sulphuretted solution; and 

 which lead to the same conclusion as the former experiments. If 

 the metals be copper and silver, the copper is at first positive, and 

 the silver remains untarnished ; in a short time the action ceases, 

 and the silver becomes positive, at the same time combining with 

 sulphur, and becoming coated with sulphuret of silver ; in the course 

 of a few minutes, the copper again becomes positive ; and thus the 

 action changes from one side to the other in succession, and is ac- 

 companied by a corresponding alternation of the electric current. 



February 20, 1S40. 

 The :\IARQUIS of NORTHA^IPTOX, President, in the Chair. 



John Caldecott, Esq., was balloted for, and duly elected into the 

 Society, 



