oS NARORE 
237 
THURSDAY, JANUARY 12, 1882 
CLERK MAXWELL’S “ELECTRICITY AND 
MAGNETISM” 
A Treatise on Electricity and Magnetism. By James 
Clerk Maxwell. Second Edition. (Oxford: At the 
Clarendon Press, 1881.) 
An Elementary Treatise on Electricity, By James Clerk 
Maxwell. Edited by William Garnett, M.A. (Oxford: 
At the Clarendon Press, 1851.) 
HESE volumes have a melancholy interest for the 
student of electrical science, inasmuch as they are 
the unfinished work of one of its great masters. The 
printing of the second edition of the larger work had 
reached the second half of the first volume when it was 
_ interrupted by the premature death of the author. Up 
_to this point considerable modifications have been intro- 
duced into the work; but the rest is merely a reprint 
under the superintendence of Mr. W. D. Niven, of Trinity 
College, Cambridge. 
We shall allude by and by to these alterations in the 
earlier part of the new edition ; but it may not be without 
interest to the readers of NATURE briefly to review the 
progress of electrical science during the eight years that 
have elapsed since the publication of the first edition, 
and to trace the influence of the work therein. 
Clerk Maxwell appeared avowedly as the mathematical 
expositor of Faraday ; in this he was the pupil and fol- 
lower of Sir William Thomson. The electrical papers 
of the last, reprinted the year before Maxwell’s work 
appeared, reach some of them as far back as 1842 ; and 
in the earliest of them he occupies himself with the trans- 
lation of Faraday’s ideas into the ordinary language of 
Mathematical Physics. He shows that his translation 
leads to a theory in no wise contradictory of the received 
theory of action at a distance, so far at least as this theory 
merely exhibits the facts of observation; but to a theory 
in some respects more comprehensive, inasmuch as certain 
experimental facts find a much more natural explanation 
in it than in the older and more prevalent one. It may 
be asserted, without fear of contradiction, that Sir William 
Thomson was the first who thoroughly understood and 
clearly expounded Faraday. Abroad his methods and 
conceptions were decried as vague and, although sugges- 
tive and worthy of notice, as the machinery that had been 
used by a man of genius, yet devoid of accurate founda- 
tion. At home the loose way in which Faraday’s methods 
and terms had been used, or more properly speaking, 
abused by many, gave but too specious a confirmation of 
the justice of this criticism. 
What Thomson began Maxwell continued, and in a 
sense completed. In his work we have the first syste- 
matic exposition of Faraday’s theory ofa dielectric medium 
applied to all the main phenomena of electricity. 
He shows, for the first time, that all the ordinary 
phenomena of electrical action and reaction can be ex- 
plained by the thoroughly legitimate physical hypothesis 
* If the reader wishes to see how much Maxwell’s work has done to 
popularise Faraday’s ideas abroad let him consult the electrical papers that 
have appeared of recent years in Wiedemann's Anna/en, or read the em- 
_ phatic testimony of Helmholtz, given at the commencement of the Faraday 
lecture. See Jour. Chem. Soc., June, 1881. 
VOL. xxv.—-No. 637 
of s¢vesses in the medium of having a static or a kinetic 
origin, as the case may be. 
Had this innovation been a mere matter of the trans- - 
formation of surface into volume integrals (as may still 
seem perhaps to some who are mathematicians by birth, 
and physicists by application only), it would not be 
necessary to dwell on it in these pages. But it was far 
more. To the old theory of action at a distance, in so 
far as it assigned the mathematical laws of certain of the 
observed facts, there could be no sort of objection. Its 
success in this respect is scarcely rivalled by that of the 
corresponding artifice in celestial dynamics. 
But the theory of action at a distance was not, and 
never could be, a dynamical explanation of electrical 
phenomena. It may be true that we know little of what 
occurs in the medium between electrified conductors ; 
but we are not likely to extend our knowledge by adopting 
a theory whick begins by directing us to divert our atten- 
tion altogether from the very field in which a dynamical 
explanation szzst be sought. This strong argument 
against it is supported by the still stronger, that, notwith- 
standing the admirable accuracy with which the oid 
theory explains a large body of facts, there are still other 
facts, continually increasing in number, of which it gives 
no explanation whatever, if ee they do not flatly 
contradict it. 
The medium theory was therefore a first and necessary 
step towards a dynamical theory of electricity. It begins 
by divesting the facts of all hypothetical raiment, and 
expressing them in language appropriate to themselves, 
suggesting nothing but what Nature has indicated, indi- 
cating nothing that Nature has denied, supposing as 
little as may be where nothing has been revealed. Above 
all banishing from the catalogue of physical conceptions 
the imponderable electrical fluids that have worked such 
mischief in indolent minds, and poisoned electrical litera- 
ture so long. 
Moreover the old theory, although it was a weapon of 
wonderful power in the hands of expert mathematicians, 
was difficult of translation into even technical verbal ex- 
pression, It was inflexible and unwieldy when applied in 
general explanation, and in the universally occurring cases 
where approximate estimation is all that is necessary or 
desirable. In one sense therefore Maxwell’s treatise was 
a popularisation of the theory of electricity. By this we 
do not mean that Faraday’s method of lines of force 
brings the subject to the level of a mind untrained in the 
handling of accurate ideas, but simply that it often renders 
the profound and laboriously acquired skill of the mathe- 
matical expert unnecessary. In the highest sense, viz. that 
of an accurate thinker, Faraday himself was, as has been 
often said, a great mathematician; although he was so 
little of a mathematical expert, that he once expresses his 
obligation to one who had calculated the tangents of some 
galvanometer deflections for him. And yet complaints 
have often been made of the obscurity of Clerk Maxwell’s 
work, Certainly it is not easy reading; but the difficulties 
are always to be found where Nature has herself set 
them; they arise simply because the author refuses to 
put a bridge over the gap presented by experience. Such 
complaints come alike from the mathematician in search 
of an ideal logical completeness, and ever impatient of 
facts that do not fit with his preconception; and from 
M 
