﻿of finding the Forces acting in Magnetic Circuits. D5 



to introduce errors. My results at higher inductions were 

 so similar to Bosanquet's that they are not worth reproducing. 



§ 9. With regard to the formula not applying with non- 

 magnetic gaps of sensible dimensions parallel to the lines of 

 induction — as when Bosanquet separated the bars by wood 

 and paper — the explanation is obvious. The lines of induction 

 no longer leave the surfaces normally, and the conditions 

 postulated by the formula are not in existence. 



§ 10. Resulting position of the Theory. 



When the bars are in contact, the stress theory, and what 

 I will call the magnetic fluid theory, lead to the same result. 

 Which is true certainly within about five per cent., and may 

 be exactly true. 



In any case, measuring tractions is not the way to get 

 accuracy, though I have no doubt that rather better results 

 could be got by going into the matter more elaborately than 

 was done either by Bosanquet or myself. 



In what follows I shall suppose that the theory is true, and 

 that the real cause of magnetic forces is to be sought in some 

 condition of the aether mechanism which receives a sufficient 

 statistical definition from the Induction Diagram. 



§ 11. The effect of varying the kind of iron employed should 

 be the same as varying the induction-density — at least in so 

 far as the phenomenon can be considered to depend on perme- 

 ability. 1 used induction-densities of from 2000 to 18,000, 

 but could not detect any effect — when the cause of error 

 referred to above was eliminated. I also used all kinds of 

 iron, from annealed Swedish iron to ordinary cast iron. I 

 varied the lengths of the bars from 60 cm. to 6 cm. — and 

 the diameter from about 2 cm. to about *6 cm. 



In no case could I detect any deviation from the predicted 

 traction which could not be explained by unavoidable experi- 

 mental errors. With short bars and high inductions necessi- 

 tating the use of very strong fields, some induction is included 

 by the testing-coil which does not help the traction and which 

 tends to make the calculated traction appear too large. 

 When this source of error was eliminated, no greater dis- 

 crepancies were observed with short bars than with long 

 ones. 



§ 12. I conclude therefore 



(1) The traction produced by a given tube of induction 

 when running out of air into iron and crossing the surface 

 normally is independent of the nature of the iron, or of its 

 form. I had a difficulty in bringing myself to believe this, 

 but the conclusion seems inevitable. 



