﻿150 Notices respecting New Books. 



general use of the term, besides bringing the subject more into 

 line with the theory of strain and stress in general. " So far we 

 have considered the two forces, electric and magnetic, producing 

 four fluxes, two involving storage and two waste of energy " t (p. 2b), 

 the existence of one of these fluxes (namely, the magnetic conduction 

 current) being quite problematical, but nevertheless postulated (as 

 appears farther on) for the purpose of giving formal completeness 

 to the cross connexions of electric and magnetic phenomena, and 

 allowing us to dispense with Maxwell's Vector Potential, 



Thus, in Mr. Heaviside's notation, the systematic, concise, and 

 fundamental equations of the electromagnetic field are simply the 

 following : — 



D=cE, B =i uH, C=£E, K=#H, 



jo = div D, a= div B, 



C+T)+pq= curl(K-h -h\ 



K+B + aq=— curl(E-0 o -<), 



in which p and c at a point are volume-densities of electrification 

 and " magnetification," q is the vector of velocity at the point if the 

 medium is moving, K is the magnetic conduction current at the 

 point, the other quantities being pretty generally recognizable, 

 while K, g, a are all of doubtful existence (see more particularly 

 p. 539 of Vol. II. of the ' Papers '). 



With regard to Mr. Heaviside's notation for vectors — viz., 

 Clarendon type — it may be said that its adoption is impossible for 

 the simple reason that we cannot use it, or anything like it, in our 

 manuscript work ; unless, indeed, in addition to pen, ink, and 

 pencil, we keep beside us a camel's-hair brush with a plate of 

 indian ink, and then paint in our vectors when they occur in the 

 work, after the slow manner of the Chinese. Mr. Heaviside is 

 conscious of this difficulty, and he suggests (p. 142) that in 

 manuscript work we should have some distinctive mark for vectors, 

 such as a suffix ; so that the vector of electric force-intensity 

 might be written E . There are two objections to this : firstly in 

 the case of such a vector, for example, as that of intrinsic electric 

 force in a medium, for which Mr. Heaviside uses e (in Clarendon 

 type) we should be obliged to write e 00 in MS. — which is intoler- 

 able, as are also B 10 &c. ; and secondly it is very undesirable to 

 have our ordinary work (with which we are most concerned, and 

 to which we become most accustomed) written in one language, 

 while our books are written in another ; there is a loss of time 

 generated by the unfamiliarity involved in the process. At the 

 same time, Clerk Maxwell's terrible German letters are not to be 

 tolerated for a moment. Perhaps a horizontal bar over the letters 

 is the best, though this is not good. 



We are now brought to the consideration of certain other pecu- 

 liarities of Mr. Heaviside's work. Maxwell was, apparently, the 



