PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 613 



Mr. Smith said that any two magnets would react upon each 

 other when brought near together, and thus there would be a 

 greater combined force than the sum of the forces of the two 

 acting separately. The telegraphing apparatus of Mr. Hughes 

 adopts the principle of using a permanent and an electro-magnet 

 in connexion with each other ; and many other experimenters 

 have used the same feature. 



Mr. Churchill said that two permanent magnets, with a sepa- 

 rate force of four each, would give a greater force than eight 

 when combined. He suggested, as a reason, a molecular change 

 produced in the steel. It has been found that soft iron, sub- 

 jected to the influence of the Rumhkorf coil, becomes so hard 

 that it cannot be filed ; whereas, upon removing it, it becomes 

 soft again. 



Mr. Eddy stated that Mr. Hughes merely neutralized the per- 

 manent magnet with the other, but did not make the two cur- 

 rents flow together, as Mr. Holcomb did. 



Mr. Dibben said that he had alluded to Mr. Hughes in saying 

 that something similar had been done, but not the same that 

 Mr. Holcomb accomplishes. 



Dr. Van der Weyde explained more fully the action of magnets 

 upon each other. Take four steel magnets, carrying two pounds 

 each, and put them together, and, instead of eight pounds, they 

 would only carry about three pounds, because the similar poles 

 being placed together counteract each other. It is not possible 

 to have a power out of a combination of horseshoe magnets equal 

 to the sum of them all. In an electro-magnetic machine with 

 seven magnets, each carrying alone sixteen pounds, the seven 

 could scarcely carry fifty pounds. But if the magnets are placed 

 end to end, the force will be more than doubled, for they react 

 upon one another. 



The President. — Does this submit to Carnot's law? 



Dr. Vander Weyde replied that he did not question that, but 

 that there were some peculiar circumstances not to be overlooked 

 in the influence of the magnets upon each other. 



Mr. Dibben did not question the facts, but asked for the 

 cause — whether it arose from an increase of battery action. 



Mr. Smith and Dr. Van der Weyde stated that the battery 

 action is increased. 



The President. — That brings it within Carnot's law. 



Mr. Seely gave a historical account of various steps in tele- 



