126 



HENEY A. ROWLAND 



where C is a constant, and x is measured from the centre. The distri- 

 bution will then be as follows : 



This distribution is not the same as that given by M. Jamin; but as 

 his method is so defective, and his " normal magnet " so indefinite, the 

 agreement is sufficiently near. 



The surface-density at any point of a magnet is 



d = 



(25) 



which, for the same kind of steel, is dependent only on ? and -3- 

 Hence in two similar magnets the surface-density is the same at similar 



.1 .2 .A .4 .5 



FIG. 8. Distribution on "normal magnet." 



points, the linear density is proportional to the linear dimensions, the 

 surface integral of magnetic induction over half the magnet or across 

 the section is proportional to the surface dimensions of the magnets, 

 and the magnetic moments to the volumes of the magnets. The forces 

 at similar points with regard to the two magnets will then be the same. 

 All these remarks apply to soft iron under induction, provided the 

 inducing force is the same and hence include Sir William Thomson's 

 well-known law with regard to similar electromagnets; and they are 

 accurately true notwithstanding the approximate nature of the formula 

 from which they have here been deduced. 



Our theory gives us the means of determining what effect the boring 

 of a hole through the centre of a magnet would have. In this case R' 



