SEPTEMBER 7, I916] 
NATURE - 
subjects, is sure to prove of great service to ad- 
vanced students. A valuable chapter on applied 
electricity is introduced, in which is a welcome 
section on the harmonic analysis of curves. The 
chapter on electric oscillations is.one of the best 
in the volume. Prof. J. Zenneck’s. photographs 
of oscillatory discharges, two of which are here 
reproduced by the courtesy of the publishers, are 
excellent, as are the descriptions of the laboratory 
experiments that may be carried out in illustra- 
tion of various branches of the subject. In a 
footnote to p. 444 is found a reference to the fact 
that the ratio of the electromagnetic to the elec- 
trostatic unit of charge has the dimensions of a 
velocity, followed by the startling statement: 
“The theory of electrical dimensions is otherwise 
of little interest.’’ In view of the practical ad- 
vantage to be gained by testing the dimen- 
sions of the terms of an equation and the 
stress laid recently on the principle of 
similitude or dynamical similarity, such an 
attitude cannot be justified. 
In the chapter on the conduction of elec- 
tricity through gases the author is scarcely 
fair to research carried out in this country. 
The corpuscular view of the kathode 
rays seems to have been advanced first 
by Varley in 1871, and the investigations 
of Sir W. Crookes surely deserve further 
description. In the account of the measure- 
ment.of the ratio of the charge to the mass 
for the kathode particles Mr. Pidduck is 
less than just to the work of Schuster 
described in his second Bakerian lecture 
(1890) and to the experiments of Sir J. J. 
Thomson shown in a lecture delivered 
before the Royal Institution (Electrician, 
May 21, 1897). Kaufmann’s paper was 
communicated to the Annalen on the same 
date. | Wiechert’s earlier experiments, 
“which did not go beyond the previous 
work of other observers” (‘The Progress 
of Physics,” Schuster, p. 68, 1911), were 
described in a _ lecture delivered on 
January 7, 1897. The experiments of 
Richardson and Compton in America 
on the photo-electric effect were carried 
out almost at the same time as those of 
Hughes .at. Cambridge. - Millikan. has just 
shown that it is possible to get very accurate 
values for Planck’s constant, h, by the use of 
this method. A useful summary of fundamental 
physical quantities is given on p. 513. The name 
“Boltzmann’s constant ” is assigned by the author 
to the constant of molecular energy, a. It is usual 
to give this name to the entropy constant, k, 
which has a value 3 a. 
The concluding chapters deal with radioactivity, 
as exhibited by radium and its derivatives, and 
the mathematical theory of electrons. The illus- 
trations include a number of C. T. R. Wilson’s 
remarkable cloud photographs showing the tracks 
of ionising particles in gases. 
ic Us Ho = 
NO. 2445, VOL. 98] 
EGYPTIAN ASTRONOMY AND THE 
ZODIAC, 
[ibe a recent number of the Bulletin de l'Institut 
Francais d’Archéologie Orientale (exii.) of 
Cairo, M. Georges Daressy, one of the foremost 
among French Egyptologists, treats of the know- 
ledge of the constellations in ancient Egypt. His 
article is entitled “L’Egypte Céleste,” by which 
words he means the duplication of the geography 
of the Nile valley into the sky, for the priests 
mentally projected another Egypt into the northern 
heavens. By a kind of symbolic celestial geo- 
graphy the daily solar journey was considered as 
a descent or voyage of the sun upon a’ river, the 
duplicate of the Nile, but situate in the firmament. 
This conception having been evolved, to render 
Double zodiac of the French Archzological Institute at Cairo, 
the allegory geographically complete, it became 
necessary to have a series of “momes,” or 
counties, alongside the celestial river upon the 
banks, the district deities of which should corre- 
spond with those of similar sites through which 
the terrestrial Nile wended its way. For this 
purpose they selected the path of the ecliptic and 
identified that with the Nile’s course. Precisely 
as each Nilotic ““nome” possessed its own deity 
with his, or her, special totem symbol, so the 
Egyptian “wise men” provided parallel deity 
figures for their celestial river upon which the sun 
voyaged. With this object they adopted the 
zodiacal signs—the decans, the planets, and 
various constellations—because they required 
stellar associations, not only for the forty-two 
