NOVEMBER 26, 1903] 
Wilson to the direct determination of the absolute 
number of ions present, and therefore of the individual 
charge carried by each ion. These are discussed in 
chapter vi., and lead to the same conclusion, that the 
charge is equal to that of the hydrogen ion in electro- 
lysis. In chapter v. the ratio e/m of the charge to 
the mass is determined for the rapidly moving charged 
particles shot out by radium, by metals in vacuo under 
the influence of ultra-violet light, and by the kathode 
in the form of the kathode ray in the electric discharge 
through highly rarefied gases. A combination of the 
values of e found in chapters ii. and vii. with the ratio 
e/m found in chapter v. leads to the conclusion that 
m must be of the order of one-thousandth of the mass 
of che hydrogen atom. 
On this is based the author’s ‘‘ corpuscular theory 
of electricity.’’ The corpuscles—and it is to be noticed 
that the term electron is not used—are the discrete 
particles of negative electricity the presence or absence 
of which determines negative and positive electrifi- 
cation, and since the value e/m for the positive ion is 
never greater than for the hydrogen ion, it is con- 
cluded that a positive corpuscle does not exist, and the 
positive ion consists of the whole atom less one 
corpuscle. 
The reader at this stage of the reasoning will prob- 
ably question the propriety of thus combining the 
values found for e and e/m, for the two quantities 
have been determined for ions of completely different 
character. An earlier and more consecutive discussion 
of the dual character of the ion, according as to 
whether its charge or its energy is its chief experi- 
mental characteristic, and the adoption of some dis- 
tinction in the nomenclature between the ions of the 
two classes, would no doubt have made the subject 
more clear. But it must be admitted also that this 
distinction, and the assumed identity of the charge 
for the two classes, is a point of weakness in the other- 
wise strictly consecutive train of reasoning. The 
critical stage of transition, where the ions of the first 
class change into the ions of the second—the slow 
diffusing negative ion in gases at high pressure, for 
example, acquiring under the action of an electric 
field, as the pressure of the gas is reduced, the energy 
and velocity of the kathode ray—seems to need further 
experimental study; for the conclusion that it is 
brought about by the ion shedding its attendant cluster 
of molecules and then travelling free seems mainly 
a consequence of regarding e as invariable. Although, 
no doubt, the arguments in favour of doing so are 
very strong, yet they appear somewhat indirect, and 
the anomaly that the slower moving ion is less effective 
as a nucleus for the condensation of moisture (p. 153) 
shows that the arguments are not all in its favour. 
The view expressed in the chapter on ionisation by 
incandescent solids that the corpuscles exist in free 
motion inside metals and carbon, from which they 
escape when their kinetic energy is increased by rise 
of temperature, is, as the author points out, of great 
importance in its bearing on the variation of chemical 
affinity with temperature. Indeed, this book will be 
read by chemists with interest for the light it throws 
on the possible causes underlying phenomena often 
NO. 1778, VOL. 69] 
NATURE 75 
considered 
familiarity. 
The chapter on Becquerel rays is the longest in the 
book, and comprises a brief review of the most im- 
portant work in radio-activity up to the commence- 
ment of the present year. Special prominence is given 
to the work of Rutherford, whose application of the 
ionisation theory to the problems of radio-activity has 
been so fruitful of discoveries. The applications of 
the theory to the spark discharge, the electric arc and 
the phenomena of the vacuum tube are treated very 
fully, and the last chapter includes a discussion of the 
important results of Kaufmann on the variation of 
e/m with v for the rapidly moving negatively charged 
particle from radium. The view is expressed that these 
results accord with the possibility that the whole of 
the mass of the corpuscle is electrical in origin. 
The treatment, although exhaustive, is confined 
strictly to the subject-matter of the title, and the recent 
advances in spectroscopy of the inner constitution of 
the atom find no place. It is interesting to notice that 
Prof. Thomson frankly abandons all attempt to dis- 
tinguish in nomenclature between the two forms of 
radiation,’’ the undulatory and the corpuscular, with. 
which modern physics now has to deal. Both are 
designated ‘“‘ rays,’’ and this extension of meaning, 
which is practically inevitable, is, of course, in strict 
accordance with the original Newtonian sense of the 
word. Kauss 
simple merely on account of their 
AN ENGLISH EDITION OF “ ASTRONOMY 
FOR EVERYBODY.” 
Astronomy for Everybody. A Popular Exposition oft 
the Wonders of the Heavens. By Prof. Simon 
Newcomb, LL.D., with an introduction by Sir 
Robert S: Ball} LED!) ERis; Bp xv-34n. 
(London: Isbister and Co., Ltd., 1903.) Price 
7s. 6d. 
HEN a popular exposition of the wonders of the: 
heavens is written by such a man as the dis- 
tinguished author of this volume, the reader, and more- 
especially he who is greatly inclined to this science, 
naturally expects to find not only new ideas in the art 
of expressing difficult issues in simple language, but 
judgments on various doubtful points by one who» 
is in the foremost rank of his work. The book before 
us is intended, as the title indicates, for the general 
reader, and should therefore be not only clear, con- 
cise, and accurate, but should be illustrated with the- 
best diagrams and pictures of the period. The reader 
will therefore be very disappointed to know that this. 
standard of excellence is by no means reached in these 
pages. 
The general scope of the book is as follows :—First, 
the general ideas of the motions of the celestial bodies 
are dealt with, the reader being also briefly introduced’ 
to the chief kinds of instruments employed in investi- 
gating the motions and physical conditions of these 
bodies. The sun, moon, earth, planets and their 
satellites are next each described, then comets and 
meteors come in for their turn, while a general review 
of the fixed stars fills up the remaining portion of the 
book. 
