Dr. C. Fromme on the Magnetism of Steel Bars. 303 

 A dependence of the diminution of ^- on the magnitude of 



the difference E— U or of the ratio yr does not follow. In 



opposition to this, M. Bouty, in a more recent notice*, main- 

 tains, on the ground of a series of experiments, of which he 



A 



adduces the following as an example, that his ratio . _^ , which 



corresponds to my =p-, decreases when the magnetizing force 



"R 



increases, according to which ^— would increase. (Whether 



his needles were annealed before each series of experiments, 

 or if they possessed initial magnetism, is not stated.) 



Needle of 0*553 millim. diameter. 

 Magnetizing A 



force. A-B' 



10 1*280 



14 1-246 



18 .... . 1-165 



22 1-150 



26 1-115 



30 1-085 



34 1-058 



38 1-036 



42 1-025 



Although here is unquestionably a diminution of -? ^, yet 



-A — _t> 



our author errs fundamentally, or at least expresses himself 

 quite incorrectly when he asserts of this ratio, " II tend vers 

 zero." An approximation to nil is certainly out of the ques- 

 tion; at the utmost there may be an approximation to unity. 



While, then, according to M. Bouty's experiments, R x and 

 R are continually coming nearer to equality, so that finally a 

 single impulse will produce the moment of saturation, accord- 

 ing to mine they are always receding further and further from 

 each other, so that the saturation-moment corresponding to a 

 force is always difficult to attain. 



On what causes these opposite results depend we cannot at 

 present say. M. Bouty's quantities are not expressed in abso- 

 lute measure ; and from his data it is not possible to reduce 

 them thereto. Yet I do not give up the expectation that his 



* Comptes Rendus de VAcad, des Sciences, 1875, jSTo. 13. 



