232 HENRY A. KOWLAND 



which can only be obtained, I suppose, from practically making the 

 machines and seeing how much faster they may be run without flying 

 to pieces. As far as this theory goes, the increase comes not from the 

 size of the machine, but from the fact that we can get a greater electro- 

 motive force with the same angular velocity, and so can reduce the 

 internal resistance in proportion. In very large machines we can make 

 the wire with one turn, not several turns simply bars on the machines. 

 We thus decrease the resistance of the machine, and at the same time, 

 if we run it above this proportion which I have pointed out, we obtain 

 the proper electro-motive force. In other words, the proper electro- 

 motive force is more easily obtained from the large than the small 

 machine, because it is not practically necessary to decrease the velocity 

 so as to keep it inversely as the square of the size. 



[Discussion by Professor Elihu Thomson and others.] 



With respect to Mr. Thomson's remarks, I am very glad to see the 

 matter taken up in this spirit and to have my principles intelligently 

 criticised. However, there was one remark which I wish to state imme- 

 diately as an error, of course, with regard to the steel. Steel can be 

 magnetized to exactly the same degree as soft iron. There is no differ- 

 ence between soft iron and steel in that respect, except that we require 

 an immensely greater force to magnetize steel to the same extent as 

 iron. There are some old papers of mine, which were published in the 

 ' Philosophical Magazine/ I believe, in 1873, relating to experiments 

 where I took iron and steel and several other metals, and showed that 

 the maximum magnetization was the same in all cases. 



But with respect to a number of statements with regard to flat mag- 

 nets and round magnets I am very glad to see my remarks criticised in 

 the manner that they were, because it shows the need of exactly what 

 I stated; and that is experiments upon this subject. The question is 

 one of quantity. My reasoning gave results in one direction, and Mr. 

 Thomson gave reasons for making the magnet in another way, and it is 

 a quantitative question of course as to which is the best; and for that 

 reason I want very much to see experiments made in the manner which 

 I have described by means of this ' magnetic proof plane/ so as to find 

 out what the escape of the lines of magnetic force in all cases is. 



I think we can decide on one point that was brought up without any 

 trouble, and that is with respect to the dynamo made with extended 

 pole piece (Fig. 2), where it was assumed that the lines of force had a 



