300 Royal Institutio7i of Great Britain. 



ings attached to and implied by the chemical signs and characters 

 used by the alchemists and the old chemists, illustrating them by nu- 

 merous drawings. 



Afterwards, the beautiful machine constructed by Mr. Bate of the 

 Poultry, for producing at once engravings of medals by machinery 

 applied to the surface of the medal itself, or to that of a cast from it, 

 was shown and explained by Mr. Faraday. Drawings would be re- 

 quired to make the description intelligible here. A plate was partly 

 engraved, and many impressions from other plates were shown. Mr. 

 Bate is still engaged in perfecting this instrument. 



Feb. 10, — Dr. Ritchie on the Laws of Action in an elementary Galva- 

 nic battery, and their application to the laws of a compound battery. 



Dr. Ritchie first endeavoured to show that the experiments adduced 

 in support of the electro-motive theory of Volta were unfounded, and 

 that decided voltaic effects could be produced by one metal and one 

 fluid ; and then attempted to account for the deflection of the needle, 

 and the decomposing powers of an elementary battery, without sup- 

 posing any actual transfer of the electric fluid from the zinc, through 

 the fluid, to the copper plate, by the definite arrangement of the mo- 

 lecules of water, and toshowalso that some of the experiments which 

 had been adduced to prove the existence of an actual current were in- 

 valid. The law which connects the conducting power of liquids in an ele- 

 mentary battery, with the distance between the plates, was examined. 

 It was shown that for moderate distances, the electro-magnetic ef- 

 fects are nearly inversely the square roots of the distance between 

 the plates ; but that when the distance is much increased, the devia- 

 tion from this law becomes apparent by a more rapid diminution of 

 electro-magnetic efforts with every remove of the plates. He then 

 showed that this law lies at the foundation of the theory of the com- 

 pound battery J and that the effects of two unequal batteries were 

 nearly as the square roots of their lengths. When their lengths were 

 much extended, as in the case of an elementary battery, the increase 

 of power began to deviate from this law, and seemed to verge con- 

 stantly towards a limit, beyond which any increase in the number of 

 plates would diminish their powers. 



Feb. 17. — Mr. Faraday gave an account of the first two parts of his 

 recent researches in electricity 5 namely, volta-electric induction, and 

 magneto-electric induction. 



If two wires, A and B, be placed side by side, but not in contact, and 

 a voltaic current be passed through A, there is instantly a current pro- 

 duced, by induction, in B, in the opposite direction. Although the 

 principal current in A be continued, still the secondary current in Bis 

 not found to accompany it, for it ceases after the first moment ; but 

 when the principal current is stopped, then there is a second current 

 produced in B, in the opposite direction to that of the first produced by 

 the inductive action, or in the same direction as that of the principal 

 current. These induced currents are so momentary that their effect 

 on the galvanometer is scarcely sensible ; but when they are passed 

 through helices containing unmiignetized steel needles, they convert 

 them into magnets. 



If 



