146 PETER GUTHRIE TAIT 



We may then write/ for i/r and 



= I 

 J o 







If we suppose the line to be in the axis of x, this gives 



... xz xy 



<7 = / (O) -f- 7 K r 



T(y^ ~f- z^j T (y^ -\- Zj 



an exceedingly ugly form for a thing derived from so symmetrical a beginning. 

 But this cannot be avoided if the algebraic sum of the masses is finite. 

 If it is o, we may treat it as magnetic matter. 

 If, in a region I,' in which there is magnetization, the intensity of magnetization be 



3 = iA +JB + kC 

 and if /= ijr, where r is the distance between xyz and x'y'z', then 



P 



'* A 



= jjjA (x - *) + B(j-y) + C(z'- M) dx , dy ,^ 



Also 

 where F= jfj C ^~^ ^^'^dxdy'dz', &c. 



or 



All this occurs in passing from the old theory of magnetism to the electro- 

 magnetic. 



I have put down a lot of imitations of your jargon mainly that you may check 

 me in any solecism. I think if you are making a new edition of 4nions you should 

 give prominence to the rules defining the extent of the application of symbols such 

 as V, S, T, U, K, &c., which are consecrated letters, not to be used for profane 

 purposes ____ 



What do you make of this ? 



You say that the constituents of T are potentials with densities &c. Well, 



47T dx 



then, take P=i/r and dP/dx=-x/r* &c., then the constituents of T will be xfiirr 

 &c. or 



and VT = . - = P, a scalar. 



?r r 



