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LO iis ae a ie ee, eee 
NATURE 
[April 24, 1873 
interest when he has arrived so far, give up the further 
pursuit of scientific work. When the governors of any 
institution can bring men up to this point, and can 
then supply them with the necessary means, they may 
consider that their work is finished. 
CLERK-MAXWELL’S ELECTRICITY AND 
MAGNETISM 
A Treatise on Electricity and Magnetism. By James 
Clerk-Maxwell, M.A., F.R.S., Professor of Experimental 
Physics in the University of Cambridge. (Clarendon 
Press Series, Macmillan & Co., 1873.) 
N his deservedly celebrated treatise on “ Sound,” the 
late Sir John Herschel felt himself justified in saying, 
“Tt is vain to conceal the melancholy truth. We are fast 
dropping behind. In Mathematics we have longsince drawn 
the rein and given over a hopeless race.” Thanks to Her- 
schel himself, and others, the reproach, if perhaps ¢/ev just, 
did not long remain so. Even in pure mathematics, a sub- 
ject which till lately has not been much attended to in Bri- 
tain, except by a few scattered specialists, we stand at 
this moment at the very least ona par with the ¢/7fe of the 
enormously disproportionate remainder of the world. The 
discoveries of Boole and Hamilton, of Cayley and Syl- 
vester, extend into limitless regions of abstract thought, 
of which they are as yet the sole explorers. In applied 
mathematics no living men stand higher than Adams, 
Stokes, and W. Thomson. Any one of these names 
alone would assure our position in the face of the world 
as regards triumphs already won in the grandest struggles 
of the human intellect. But the men of the next gene- 
ration—the successors of these long-proved knights—are 
beginning to win their spurs, and among them there is 
none of greater promise than Clerk-Maxwell. He has 
already, as the first holder of the new chair of Experi- 
mental Science in Cambridge, given the post a name 
which requires only the stamp of antiquity to raise it 
almost to the level of that of Newton. And among the 
numerous services he has done to science, even taking 
account of his exceedingly remarkable treatise on “ Heat,” 
the present volumes must be regarded as pre-eminent. 
We meet with three sharply-defined classes of writers 
on scientific subjects (and the classification extends to all 
such subjects, whether mathematical or not). There are, 
of course, various less-defined classes, occupying inter- 
mediate positions, 
First, and most easily disposed of, are the men of calm, 
serene, Olympian self-consciousness of power, those upon 
whom argument produces no effect, and whose grandeur 
cannot stoop to the degradation of experiment! ‘ These 
are the @ priori reasoners, the metaphysicians, and the 
Paradoxers of De Morgan. re 
Then there is the large class, of comparatively modern 
growth, with a certain amount of knowledge and ability, 
diluted copiously with self-esteem—haunted, however, by 
a dim consciousness that they are only popularly famous 
—and consequently straining every nerve to keep them- 
selves in the focus of the public gaze. These, also, are 
usually, men of “paper” science, kid-gloved and black- 
coated—with no speck but of ink. 
Finally, the man of real power, though (to all seeming) 
perfectly unconsci6us of it—who goes Straight to his 
mark with irresistible force, but neither fuss nor hurry— 
reminding one of some gigantic but noiseless “crocodile,” 
or punching engine, rather than of a mere human being. 
The treatise we have undertaken to review shows us, 
from the very first pages, that it is the work of a typical 
specimen of the third of these classes. Nothing is as- 
serted without the reasons for its reception as truth being 
fully supplied—there is no parade of the immense value 
of even the really great steps the author has made—no 
attempt at sensational writing when a difficulty has to be 
met ; when necessary, there is a plain confession of igno- 
rance without the too common accompaniment of a sick- 
ening mock-modesty. We could easily point to whole 
treatises (some of them in many volumes) still accepted 
as standard works, in which there is not (throughout) a 
tithe of the originality or exhaustiveness to be found in 
any one of Maxwell’s chapters. 
The main object of the work, besides teaching the ex- 
perimental facts of electricity and magnetism, is every- 
where clearly indicated—it is simply to upset completely 
the notion of action at a distance. Everyone knows, or 
at least ought to know, that Newton considered that no 
one who was capable of reasoning at all on physical 
subjects could admit such an absurdity: and that he 
very vigorously expressed this opinion. The same negation 
appears prominently as the guiding consideration in the 
whole of Faraday’s splendid electrical researches, to 
which Maxwell throughout his work expresses his great 
obligations. The ordinary form of statement of Newton’s 
law of gravitation seems directly to imply this action at a 
distance ; ard thus it was natural that Coulomb, in stating 
his experimental results as to the laws of electric and 
magnetic action which he discovered, as well as Ampére 
in describing those of his electro-dynamic action, should 
state them in a form as nearly as possible analogous to 
that commonly employed for gravitation. 
The researches of Poisson, Gauss, &c., contributed to 
strengthen the tendency to such modes of representing the 
phenomena ; and this tendency may be said to have cul- 
minated with the exceedingly remarkable theory of electric 
action proposed by Weber. 
All these very splendid investigations were, however, 
rapidly leading philosophers away towards what we can- 
not possibly admit to be even a bare representation of 
the truth, It is mainly to Faraday and W. Thomson 
that we owe our recall to more physically sound, and 
mathematically more complex, at least, if not more beauti- 
ful, representations. The analogy pointed out by Thom- 
son between a stationary distribution of temperature in a 
conducting solid, and a statical distribution of electric 
potential in a non-conductor, showed at once how results 
absolutely identical in law and in numerical relations, 
could be deduced alike from the assumed distance-action 
of electric particles, and from the contact-passage of heat 
from element to element of the same conductor. 
But we must give Maxwell’s own frank and ample 
acknowledgment of his debt to these two men. 
“ The general complexion of the treatise differs con- 
siderably from that of several excellent electrical works, 
published, most of them, in Germany, and it may appear 
that scant justice is done to the speculations of several 
eminent electricians and mathematicians. One reason 
of this is that before I began the study of electricity I 
résolved to read no mathematics on the subject till I had 
