in a Letter to M. Gay-Lussac. 287 



wire placed in any situation occupied by a cylinder, and I 

 have shown that they produce currents in their state of rota- 

 tion, if their opposite extremities are connected with the gal- 

 vanometer. 



It is said at page 284, that the formation of currents is 

 ** wholly due to another condition, they being manifested only 

 at the moment when the spirals are brought near to the mag- 

 nets, or removed from them. So long as the spirals are pre- 

 sent, whether they move or not, there is no current. So also 

 then is none in the case of central rotation" &c. Now in my 

 first paper I showed that the essential condition was not the 

 approximation or removal of the metal in movement, but 

 simply that it should intersect the magnetic curves (F. 101. 

 116. 118. &c.); and that consequently, cccteris paribus, the 

 movement without change of distance is the most effective 

 and powerful means of obtaining the current, instead of being 

 the condition in which the result is absolutely nothing. In 

 my second paper I proved that a movement through the mag- 

 netic curves was the only condition necessary (F. 217.); an d 

 that so far from the approximation or removal of the metal 

 being necessary, currents may be produced in the magnet 

 itself, merely by moving it in the proper direction (F. 220.). 



Lastly, when treating of this " central arrangement," and 

 the supposed absence of effect when " the points of the disc 

 remain constantly at the same distance from the magnetic 

 pole," Messrs. Nobili and Antinori say (p. 285.), " by thus 

 renewing the combination of continued presence to which 

 Mr. Faraday's new laws in relation to currents do not assign 

 any effect ;" and in a note we read, " These laws are reduced 

 to three," which are specified, at first fully, and then in a more 

 condensed form, as follows : " FIRST LAW. During gradual 

 approximation: the current produced contrary to the current 

 producing; repulsion between the two systems. SECOND 

 LAW. The distance unvarying. No effect. THIRD LAW. 

 During recession. The current produced in the same direc- 

 tion as the current producing. Attraction between the two 

 systems." I have never myself given these as the simple laws 

 which govern the production of the currents that I was so 

 fortunate as to discover; nor do I understand how Messrs. 

 Nobili and Antinori can say that they are my laws, though at 

 page 282 one of them is so called. But 1 described these 

 three cases together in my first memoir (F. 26. 39. 53.), as 

 well as in the notice, that is, in my letter to M. Hachette, 

 as effects that I had observed. It has been established, by 

 what I have already said, that they are not the laws of the 

 action of magnetic electricity, for the simple fact that cur- 



