PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 491 



attracting power was varied according as the distance was in- 

 creased, and that that was the only law which was taken into 

 consideration so far. One law was that in case of a magnet 

 working in contact it must have a certain amount of force. The 

 attractive force of a magnet is according as the distance is 

 increased. He thought that the pressure on the substructure of 

 the road would be increased by magnetism. You require to have 

 a perfectly smooth surface to get the full amount of attraction. 

 When this subject was experimented upon in France they had 

 not a sufficient surface in contact. 



Mr. Seely. — The last and strongest objection is that the poles 

 are constantly changing, and it is not practicable to change 

 polarity, rapidly. 



The Chairman. — Will the tendency to slip of the wheel on the 

 rail be such that a considerable amount of force would be re- 

 quired to prevent the slip ? His question was not answered. 



Mr. Hedrick thought that if there was any gain it was by the 

 force of the wheel on the rail and then applying magnetism. 



Mr. Dibben said that by getting the iron as soft as could be 

 got the first principle of. a good magnet would be obtained. Soft 

 iron was necessary for a magnet, and hard iron for the rails. 



The Chairman said there was no such thing as contact. He 

 wished to know if the weight of the engine was increased to 20 

 tons what would be the advantage gained by the increased pres- 

 sure ? 



Mr. Dibben did not think it would amount to very much. 



Mr. Garvey thought that accurate experiments made with one 

 of the locomotives would be better than all the discussion that 

 could be had on the subject. 



Mr. Fisher wished to know what the ordinary rate of travel of 

 these trains was ? 



The Chairman said it was twelve miles an hour. 



Mr, Seely moved that a committee be appointed to investigate 

 the experiments that are now making on the subject? The 

 motion was seconded and carried. 



The Chairman appointed Messrs, Seely, Dibben, and Hedrick 

 to act as a committee for that purpose. 



Mr. Seely proposed the caloric engine as a subject for discus- 

 sion at the next meeting. He stated that he was interested per- 

 sonally in the caloric engine, but did not think that that would 

 militate against it as a subject for discussion. 



[Am. Inst.] FF 



