



es es aoe 
=> a > eed 
FEBRUARY 17, 1923] 
= 
. 
During the year 1921-1922 covered by the report, the 
Association has been engaged on researches on neutral, 
_ optical, and coloured glasses, on abrasives and cements, 
for optical work, on the durability of glass, on phos- 
_ phorescent material for X-ray use, on greases and 
wax mixtures, on lacquer, on the best wave for 
generation of X-rays, on regulation and focussing of 
_ X-ray tubes, on insulators, manganin wire, and on 
galvanometer coils. The work already done by the 
Association is bearing fruit, and firms engaged in 
instrument making are finding that the saving in 
_ their working costs owing to the adoption of methods’ 
suggested by the Association thoroughly justifies 
_ their financial support of it. We are glad to be 
assured that steps are being taken to secure from the 
industry adequate means to continue the work of the 
Association after the close of the Government grant. 
period in June 1924. 
WE regret that a manuscript note on the corner of 
the first part of the Zeitschrift fiir angewandte Geo- 
_ physik led the reviewer in our issue of February 3, 
p. 145, into stating that the price of the single part was 
20s. The publishers, Gebriider Borntraeger, have 
pointed out that this sum covers the whole of the 
first volume, and we hasten to make this correction 
in the interests of a publication which they have. 
undertaken with their characteristic enterprise. 
a 
Messrs. LoncMANS AND Co. have nearly ready 
for publication ‘“‘ Synthetic Colouring Matters: Vat. 
THE GREAT RED Spot ON JupiITeR.—Mr. W. F. 
Denning writes :—The planet Jupiter is now coming 
well into view and will rise at about midnight at the 
end of February. The Great Red Spot which has 
been certainly visible, though under rather different 
Sa since 1857, is still to be distinguished. 
t should be observed as often as possible during 
the ensuing spring months, and the times of its 
transit across the central meridian carefully recorded. 
Its rate of motion last year indicated a period of 
rotation equal to 9 55" 388. During the last few 
As a guide to telescopic observers the following times 
central meridian :— 
Tits ae, h. m. 
March 6,. 14 29 March 16 I2 40 
b: ‘ 8 16: » 60a 14 18 
par gis (0 17 45 7. 2m I2 30 
p 
At the present time the spot precedes the zero 
meridian (of System II.) by about 3} hours, and this 
is increasing. There is another long, dusky marking 
in nearly the same latitude of Jupiter which closely 
follows the eastern end of the Red Spot. This will 
also well repay observation. It has been visible 
since Igol. 
Prrropic MoTION IN THE THREE-BODY PROBLEM.— 
Prof. Strémgren gives in No. 39 of the publications 
of the Copenhagen observatory a useful summary 
of the progress attained in recent years in the studies 
made there both in the restricted and the general 
problem of 3-bodies. (The former supposes one body 
infinitesimal, and the motion of the other two bodies 
circular.) The method used is that of mechanical 
quadratures, which is tedious and needs many 
successive approximations before periodic orbits are 
NO. 2781, VOL. 111] 


. 4% 
NATURE 


years the spot has exhibited a slackening of velocity. | 
are given when this marking will be on or near the | 

233 
Colours,’’ by Prot. J. F. Thorpe and Dr. C. K. Ingold. 
It will deal with the history of vat dyeing, of synthetic 
indigo and the various analogues of indigo; the 
derivatives of anthraquinone, and the preparation 
of some of the vat colouring matters. Another book 
to be published soon by the same house is “‘ Printing 
Telegraph Systems and Mechanisms,” by H. H. 
Harrison, a text-book intended for the use of the 
designer, the administration official, the technical 
telegraphist, and the student of telegraph matters. 
A NEw departure in the policy of the American 
Chemical Society is evidenced by the appearance 
(through The Chemical Catalog Co., Inc., New York); 
of a number of monographs on various branches of 
chetnical science and the issue of a long list of pro- 
jected volumes. The series is announced as “ a serious 
attempt to found an American chemical literature 
without primary regard to commercial considerations.” 
Among the monographs in preparation are: Shale Oil ; 
Coal Carbonisation ; Aluminothermic Reduction of 
Metals; The Chemistry of Leather Manufacture ; 
Liquid Ammonia as a Solvent; Wood Distillation ; 
Thyroxin ; Extraction of Gasoline from Natural Gas ; 
Refining Petroleum ; The Structure of Crystals ; The 
Properties of Metallic Substances; Solubility ; 
Valence, and the Structure of Atoms and Molecules ; 
Organic Arsenical Compounds ; Absorptive Carbon ; 
Chemistry of Cellulose ; The Properties of Silica and 
the Silicates; Piezo-Chemistry ; The Animal as a 
Converter; Cyanamide; The Corrosion of Alloys. 

Our Astronomical Column. 
found, but it has the advantage of avoiding the 
mathematical difficulties involved in theoretical work. 
The pamphlet also summarises the work of Sir G. 
Darwin and others. The connexions between families 
of orbits are traced, and it is considered that the 
treatment of the restricted problem with the selected 
mass-ratio is approximately complete. The orbits 
are divided into 16 classes comprising libration 
orbits about the 5 equilibrium points, 3 of which 
are in the line joining the finite masses, the other 
2 are the equilateral-triangle points, which were at 
first merely theoretical, but later found exemplifica- 
tion in the Trojan group of minor planets. 
The results illustrate various possibilities in the 
case of planets moving about a pair of suns. Each 
sun might have some satellites peculiar to itself, 
their motion, like that of our moon, being somewhat 
disturbed by the other. A figure-of-eight, encircling 
each sun in turn, is another possibility, while other 
orbs might pursue large orbits, in the form of distorted 
ellipses, outside both suns. But it must be remem- 
bered that periodic motion requires an exact adjust- 
ment of the initial speed and direction of motion. 
In most cases the orbits would not be periodic at all, 
but would undergo changes from one type to another. 
A beginning has now been made with the study 
of the motion with all three masses finite. The 
case first studied was that of small librations about 
the 3 equilibrium points in a rotating line. This 
was subsequently extended to orbits of ejection or 
collision, in which 2 of the bodies are together at the 
beginning or end of the time considered. A case 
of 4-body libration is also sketched. No. 40 of the 
Copenhagen Publications deals with a special case 
of the 4-body problem, with 3 equal masses in a line, 
and the fourth infinitesimal. 
