338 
A MEMORANDUM on the probable character of the 
weather in north-west India in January, February, 
and March 1923 was prepared by Dr. G. T. Walker, 
director-general of Indian observatories, and sub- 
mitted to the Government of India on January 5. 
The data which control the amount of rain and snow 
to be expected are :—(a) The recent weather conditions 
in Persia and north-west India; these are slightly 
favourable. (b) The seasonal change in the upper 
air in northern India, which is slightly adverse. 
(c) The atmospheric pressure over India in the 
previous October and November, which is neutral, 
October being above normal and November below 
normal. (d) Rainfall at Seychelles and Zanzibar ; 
rainfall at Seychelles was in defect in November and 
December, and at Zanzibar it was in excess in 
December. On the whole the indications point to 
a slight defect in the winter precipitation, but the 
indications are said not to be sufficiently pronounced 
to justify a forecast of a deficiency. 

REFERRING to the obituary notice of Prof. George 
Lunge in Nature of February 17, p. 228, a corre- 
spondent has pointed out the last paragraph might 
give the impression that Dr. Hurter was of German 
nationality whereas he was a native of Schaffhausen, 
NATURE 

[Marcu 10, 1923 

Switzerland. The writer of the notice was concerned 
rather with the influence exercised at the time by ~ 
the German universities in providing opportunities, 
not necessarily for Germans alone, for scientific — 
training as chemists, some of whom came to England 
to acquire knowledge and experience of the practical 
applications of the science. : 
WE have received from Messrs. A. Gallenkamp 
and Co. a catalogue of ‘‘ Electrometric Apparatus for 
determining Hydrogen Ion Concentrations.’ This 
includes an apparatus for determining hydrogen ion 
concentrations both for work of high accuracy and 
for routine industrial work. 
Messrs. BowEs AND Bowes, 1 Trinity Street, 
Cambridge, have just issued a very useful catalogue 
(No. 417) of second-hand books, journals, and 
portraits of scientific interest offered for sale by them. 
It contains 1158 titles, which are classified under 
the following headings: Journals, etc.; Agriculture; 
Anthropology and Ethnology ; Biography ; Biology ; 
Botany (including Forestry and Gardening) ; Geology ; 
Microscopy; Zoology (including Ornithology and 
Entomology) ; General Science ; Chemistry ; Physics 
(including Einstein Theory); Medical (including 
Physiology) ; Portraits. 

Our Astronomical Column. 
INCREASE OF BRIGHTNESS OF BETA CEtTI.—There 
appears to be no reason to doubt the news that this 
star has brightened by more than a magnitude in the 
last week or so. The change was first observed by a 
British schoolboy named Abbott, resident in Athens ; 
being a member of La Société Astronomique de France, 
he telegraphed to M. Camille Flammarion at Juvisy, 
whose assistant, M. Quénisset, confirmed the brighten- 
ing. Apparently further confirmation has been re- 
ceived from the United States. Unfortunately the 
star is observable in England only by day or in very 
bright twilight, and the skies have not been pro- 
pitious for studying it. Data for drawing the light 
curve are not yet to hand, so that it is premature to 
speculate on the probable cause of the increase of 
light. The news hitherto available comes through 
the daily press; the Astronomical Bureau at Copen- 
hagen has made no communication. 
THE Zopi1acaL Licut.—Mr. W. F. Denning writes :— 
During the period from about March 8-20 and April 
4-18, the zodiacal light may be well observed on clear 
evenings in the absence of moonlight. It will be 
visible about two hours after sunset as a faint glow 
extending upwards, obliquely, through the constella- 
tions of the Zodiac, and broadest at its base on the 
western region of the horizon. It apparently varies 
from night to night, for its visibility is evidently 
influenced by atmospheric conditions. Careful ob- 
servations of the degree of luminosity, positions, and 
boundaries of the light on successive evenings will be 
valuable. The most probable explanation of the 
phenomenon is that it is due to the sun’s reflected 
light on myriads of meteoric particles belonging to 
systems of little inclination and situated at moderate 
distances from the sun. 
THE SPECTRA OF VisuaAL DouBLE STars. — Mr. 
F. C. Leonard publishes in the Lick Observatory 
NO. 2784, VOL. T11] 

Bulletin (No. 343) an important contribution to the 
study of the spectra of visual double stars. If the 
components of a double star had a common origin, 
a knowledge of the spectral relationships existing in 
different systems, presumably at various stages in the 
course of evolution, might be expected to disclose 
the general trend and the comparative rates of 
development of these stars. It was with the inten- 
tion of gaining more knowledge on this subject that 
Mr. Leonard commenced this investigation in 1920. 
From a study of eighty visual double stars specially 
observed for this work, he finds that the spectrum of 
the secondary component of a dwarf star is generally 
of a later class and that of a giant star is of an earlier 
class than the primary. In both giant and dwarf 
stars the greater the difference in magnitude between 
the primary and secondary the greater is the absolute 
difference in spectral class. ; 
The spectrum of each component of a double star 
appears to be a function mainly of its absolute 
magnitude ; or in other words, the spectra of the 
components of double stars are so related to each 
other that, with but few exceptions, these systems 
conform to the Hertzsprung-Russell arrangement for 
individual stars, plotted according to spectral class 
and absolute magnitude. In this configuration, the 
fainter component normally precedes the brighter 
one, regardless of whether the latter be a giant or 
dwarf in the order prescribed by the Lockyer-Russell 
theory of stellar evolution. The two earlier conclu- 
sions are special phases or necessary consequences of 
this generalisation. Thirteen binary systems, all 
stars of which were dwarfs, indicated that as the sum 
of the masses of the components increased, their 
disparity in spectral class approached zero. Of any 
two stars of unequal mass but of otherwise identical 
physical properties, that with the less mass will in 
general pass through its life history in advance of the 
more massive one. 

