APR B.] DIMENSIONS 209 



where I is the intensity of magnetisation, and H the 

 intensity of the field, inside the substance of a uniformly 

 magnetised sphere of radius a and magnetic moment M. 

 The equivalent mass moving with the velocity of light 

 would therefore have an energy equal to two-fifths of the 

 intrinsic energy of the magnetised sphere. 



APPENDIX C. 

 On Electricity and Gravitation and Dimensions. 



Referring back to an article of mine in the Philosophical 

 Magazine for November, 1882, page 358, we find the 

 fundamental and necessary relation between constants 

 stated thus, where M shall stand for magnetic pole and y 

 for Cavendish's gravitation constant 



F being force and I being length. 



If it is now going to turn out that a mass is composed 

 of electric charges, it might seem as if e and m were 

 quantities of the same nature, and were only numerically 

 connected ; whence it would follow that AC and y were of 

 similar kind. In other words, Faraday's dielectric constant 

 would become closely related to Cavendish's gravitation 

 constant, and weight as well as mass would be traced to 

 electricity ; but such a deduction is unwarranted, there is 

 nothing to prevent essentially different properties of the 

 ether being involved in the two kinds of force gravitative 

 and electric. 



As to the nature of the gravitation constant itself, we 

 have 



_F 2 _ I 3 v 2 _sq. of velocity _ energy/mass 

 ^ ~~ m 2 ~~ mP ~" mjl ~~ linear density ~~ mass/length' 

 L.E. o 



