94 NATURE 
[JANUARY 20, 1923. 

trades with which they are concerned. The larger 
industries are being organised entirely by their own 
trade associations, including the British Engineers’ 
Association for mechanical engineering exhibits, the 
British Electrical and Allied Manufacturers’ Associa- 
tion for all electrical exhibits, and the Association of 
British Chemical Manufacturers ; but in the case of 
many other trades about fifty representative com- 
mittees have been set up to work in conjunction with 
the exhibition officials, and they are now holding 
regular monthly or fortnightly meetings, with the 
object of inviting exhibitors, individually or in groups, 
securing the requisite amount of space, and arranging 
and classifying the exhibits. The committees are 
getting into communication with all traders in the 
different trades. Some of the smaller traders, it is 
thought, may desire to economise by exhibiting in 
groups. Provision for this will therefore be arranged. 
Sir Lawrence Weaver, director of the United Kingdom 
Exhibits Section, is attending the meetings of these 
committees, in order to explain the nature of the work, 
and to see that the committees are enlarged, where 
necessary, to ensure their representative character. 
He has explained also that the executive committee, 
desiring to evolve unified schemes of decoration for 
each section, has obtained the services of a panel of 
eminent architects who will advise committees in 
regard to decorative schemes. 
THE annual meeting of the Circle of Scientific, 
Technical, and Trade Journalists was held in the 
Hall of the Institute of Journalists on January 9, 
when Sir Richard Gregory was elected chairman in 
succession to Mr. L. Gaster (32 Victoria Street, 
London, S.W.1), who has been chairman for the 
past eight years and has now consented to serve as 
secretary. In opening a discussion on ‘‘ Reviews 
and Reviewers,” Sir Richard Gregory referred to the 
distinctions between the points of view of publisher, 
author, and editor. The first concern of an editor 
is, however, the interests of his readers. So many 
books are received for review by leading journals 
that it is impossible to find space to notice them 
all, and a selection has, therefore, to be made. 
Books may be selected for special notice on account 
of (1) wide interest of subject, (2) eminence of author, 
(3) outstanding importance. The most readable 
review, if written with expert knowledge of the 
subject, is editorially the most acceptable and prob- 
ably best directs attention to the book noticed. 
A mere statement of contents is not a review, though 
a descriptive synopsis may serve a useful purpose. 
Readers are not interested in long lists of errors, 
and it is preferable to send such lists to publishers 
or authors instead of printing them. Books not 
selected for special reviews may be dealt with in 
short notices, but, on account of limitations of space, 
many can be mentioned only in lists of books received. 
It was the general opinion of the editors of different 
types of technical journals who took part in the 
discussion that while an unsigned review might be 
subjected to a certain amount of editing, no essential 
change should be made in a signed review. Custom 
has sanctioned the principle that a book noticed by 
a reviewer becomes his property, and the view was 
expressed that, provided a reasonable period had 
elapsed since the date of publication, books merely 
announced might be sold or disposed of in any way. 

THE Drayson PARADOX.—A pamphlet by Mr. A. H. 
Barley on ‘‘ The Drayson Problem ”’ shows that this 
curious paradox has still a considerable vogue. It 
had its origin solely in the somewhat loose language 
of certain text-books which described the motion of 
the pole of the equator as circular, the pole of the 
ecliptic being in the centre. This description would 
be correct if only the solar and lunar precessions were 
concerned, but planetary perturbations cause the 
plane of the ecliptic (and hence its pole) to shift, thus 
causing a variation in the radius of the circle. Dray- 
son, without carefully studying the evidence for the 
shifting ecliptic, asserted that it was really fixed 
among the stars, and that the centre of the north 
pole’s motion was 6° away from the ecliptic pole, 
thus bringing about a very large change in the 
obliquity, which he supposed to be near its minimum 
at present. It would reach 35° at its maximum, when 
Drayson considered an Ice-age would occur. Dray- 
son’s supporters slur over the fact that all the planet- 
ary orbit planes are changing, owing to mutual per- 
turbations, theory and observation being in good 
agreement. Further, they claim to account for stellar 
proper motions by their revised precessions, omitting 
apparently to note that motions due to a mere change 
in the earth’s axis would affect all the stars in the 
same region of space alike, whereas the actual motions 
differ from star to star, as can readily be verified 
from stellar photographs. If the Draysonians would 
study the full collection of modern observations of 
sun, planets, and stars, instead of wresting a few 
isolated observations to suit their preconceived views, 
NO. 2777, VOL. 111] 

Our Astronomical Column. 
they would soon be convinced that their hypothesis 
is not consistent with the facts, but that the ecliptic 
is actually shifting through an angle of some 47” per 
century. 
PARALLAXES OF Firty StTars.—The Sproul Obser- 
vatory has just issued No. 6 of its publications, a 
continuation of numbers 4 and 5, which contains a 
third list of trigonometrical parallaxes of 50 stars. 
The observational work has been spread over the 
years 1915-1921 and the results were obtained through 
the efforts of several persons named in the volume. 
The list includes stars of various types of spectra and 
magnitudes, the latter ranging from 2-81 to I0°5. 
This list is very opportune, as the values will assist in 
the researches now being carried out in the determina- 
tion of parallaxes by the spectroscopic method. 
VARIABLE STAR MAXIMA AND MINIMA FOR 1923.— 
Variable star observers will find the Harvard College 
Observatory’s Circular No. 241 very useful. Dr. 
Leon Campbell publishes in it the predicted dates of 
maxima and minima for variable stars of long period. 
The dates for 366 variables are inserted in the table. 
The information is given in the following form: 
first, six figures which denote the Right Ascension and 
Declination of the star; next, the name of the star 
according to the new nomenclature instituted by the 
International Astronomical Union; and, lastly, the 
dates of the maxima and minima showing the months 
and days of the month. Thus, for example, o Ceti 
or ‘‘ Mira” with R.A. 2" 14™ and Dec. — 3° reaches a 
maximum on April 2 and a minimum on October 23, 
EEE 
