H. A. Rowland— Studies on Magnetic Distribution. 103 



Numerous other cases might be represented by diagrams, as 

 of a sound being hindered or tilted upward by a concurrent 

 wind of unequal velocity, or downward by an opposing wind of 

 similar character, and of the various permutations of differing 

 currents in oblique directions ; to which might be added vari- 

 ous resultants of unequal motion producing lateral refraction, 

 but this is unnecessary. Enough has been said, it is hoped, to 

 clear from popular misapprehension, the admirable hypothesis 

 of Professor Stokes, raised by the equally admirable investiga- 

 tions of Professor Henry, to the rank of a " theory ;" and to 

 show that it has a real and demonstrated basis, or in other 

 words that it is a vera causa. The question of its sufficiency 

 lies entirely within the grasp of mathematical discussion ; but a 

 long series of accurate and comprehensive observations will yet 

 be required to discover its full compass of practical result, and 

 to determine its precise limit of capacity in subjugating the 

 " abnormal phenomena " of sound. 



by Henry A. 



(Continued from page 29.) 

 VI. 

 M. Jamin, in his recent experiments on magnetic distribu- 

 tion, has obtained some very interesting results, although I 

 have shown his method to be very defective. In his experi- 

 ments on iron bars magnetized at one end, he finds the formula 

 f'^ to apply to long ones as I have done. Now it might be 

 argued that as the two methods apparently give the same 

 result, they must be equally correct. But let us assume that 

 the attraction of his piece of soft iron F varied as some un- 

 known power n of the surface-density 6. Then we find 



which shows that the attractive force or any power of that 

 force can be represented by a logarithmic curve, though not 

 by the same one. Hence the error introduced by M. Jamin's 

 method is insidious and not easily detected, though it is none 

 the less hurtful and misleading, but rather the more so. 



However, his results with respect to what he calls the nor- 

 mal magnet* are to some extent independent of these errors; 

 and we may now consider them. 



Thus, in explaining the effect of placing hardened steel 

 * "On the Theory of Normal magnets," Comptes Rendw, March 31, 1873, trans- 

 lated in Phil. Mag., June, 1873. 



