202 
with a membership of 3,373, and an income 
of about nine thousand pounds sterling. 
There remain still two chapters to which we 
hope later to call attention in special notices, — 
one by Egli of Zurich on the present condition 
of geographic onomatology, or the study of 
names ; the other, by the editor, on the devel- 
opment of the study and method of teaching 
of geography, a matter discussed with much 
seriousness in Germany, though receiving small 
attention here. 
In concluding the present notice, it may be 
said, that while the Gleographisches jahrbuch, 
like other works of its class, by no means serves 
the purpose of final reference, it is of the 
greatest value as an aid in all geographic 
studies; and the special feature of arrange- 
ment according to place makes it a most val- 
uable supplement to other bibliographic works 
in which the classification is according to 
subjects. 
MASCART’S ELECTRICITY AND MAG- 
NETISM. 
Legons sur l’clectricité et le magnétisme. Par E. Mas- 
CART et J. JOUBERT. vol.i. Paris, 1882. 8°. 
A treatise on electricity and magnetism. By the same; 
translated by E. ATKINSON. vol. i. London, 
De la Rue, 1883. 662 pp. 89°. 
One feels, in reading Maxwell’s treatise on 
electricity and magnetism, that the author had 
a grip upon the subject which has only been 
approximately attained by other writers. Al- 
though the style is obscure, and the arrange- 
ment often merits the word ‘ atrocious,’ — for 
equations are taken for granted which are 
afterwards proved, and other equations are 
referred to in general without particular speci- 
fication ; so that the student who comes to the 
book with mediocre preparation, and is deter- 
mined to master it, cannot fail to have a feel- 
ing allied to bitterness with the author who 
has led him over such a corduroy road to a 
promised land, — nevertheless, the grip is 
there, and one always feels it; and each para- 
graph is full of suggestion. 
The treatise of Mascart and Joubert is Max- 
well’s treatise very much simplified. It has 
the Gallic flow, but it has not the Scottish 
grip. It is Cummings’s admirable little ele- 
mentary treatise on electricity, treated by the 
calculus, and amplified with some of the harder 
portions of Maxwell. It has the appearance 
of a collection of excellent professorial notes 
on Maxwell’s book. 
The volume now printed contains the me- 
chanical theory of electricity; and a second 
SCIENCE. | 
volume on the phenomena and electrical ap- 
paratus is promised. ‘The portion on thermo- 
electricity is more extended than the chapter 
on the same subject in Maxwell’s treatise ; 
although, curiously enough, Tait’s ingenious 
method of measuring thermo-electric relations 
is not given. Much space is devoted to the 
propagation of what are termed, for con- 
venience, ‘ electrical waves ;’ and the action of 
the telephone is theoretically considered. In 
the treatment of electro-dynamics the prin- 
ciple of symmetry is often employed in a clear 
manner. 
that the authors are patriotic, and the special 
investigations of Frenchmen are often alluded 
to. We miss, however, full notices of contem- 
poraneous investigations by Germans and by 
Americans. Perhaps these will appear in the 
following volume. The chapters on magnetism 
are very suggestive, and in them the various 
theories are presented in a clear manner. 
Thomson’s papers on magnetism are given at 
considerable length, mainly as they are con- 
tained in his ‘ Papers on electro-statics and 
electro-magnetism.’ ‘The view that diamag- 
netism is merely the difference between the mag- 
netic character of the medium in which the small 
diamagnetic substance is suspended, and the 
magnetic character of the substance itself, is 
popularized by presenting the analogy between 
this phenomenon of magnetism and the action 
of bodies floating in fluids of different specific 
gravities. This hypothesis makes the ether 
of space a magnetic medium, with a greater 
coeflicient of magnetization than that of any 
known diamagnetic substance. The analytic 
processes of the authors are, in general, simple. 
Laplace’s and Legendre’s coefficients are used 
only in .a limited way in the subject of mag- 
netism. Perhaps this may be regarded as an 
advantage in the treatment. What is needed 
at present is an extended treatise on the ap- 
plication of spherical harmonics to practical 
problems in electricity and magnetism, and to 
problems of attracting forces in general, in 
order to show the availability of this method 
of analysis. 
The authors treat the subject of electro- 
magnetic induction in a clear way. The re- 
tarding effect of induction on the swing of a 
galvanometer needle is clearly set forth, and 
the work of electrical motors receives some 
attention. More will probably be given in the 
next volume. Hall’s phenomenon is treated 
in a far-off manner. The authors state that 
‘¢ Hall’s phenomenon would seem to be in con- 
tradiction with the opinion generally adopted, 
that in electro-magnetic phenomena the action 
[Vou. IIL, No. 54. 
It is noticeable throughout the work 
20 
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