892 
NATURE 
[JUNE 30, 1923 

The research department, however, has perfected 
methods of eliminating the disturbances due to this 
cause, and so it is hoped that the radio method will 
be much more widely adopted in the future. During 
the last year postal and telegraph communication 
has been established with Tibet and Afghanistan. 
The Dalai Lama has given every encouragement to 
the establishment of communication between Lhasa 
and India. Afghanistan has not yet joined the 
Universal Postal Union; letters are stamped to 
India, and a charge is made on delivery, but the 
amount of this charge seems to be uncertain. In 
the discussion on the paper Colonel Edwards said 
that India offered the most wonderful possibilities 
in the way of air mail transport. For example, the 
journey from Calcutta to Rangoon took at present 
3-6 days. If an air mail service were employed the 
time taken would be only 9 hours. Many similar 
cases could be cited. In England difficulties are 
caused by fog, but in India the only fogs are the few 
that occur during the monsoon. 
WE have received from the Department of Agri- 
culture and Technical Instruction for Ireland ‘a copy 
of the catalogue of maps, memoirs, and sections 
published by the Geological Survey of Ireland. The 
list includes maps, etc., for the whole of Ireland: — 
they are now to be obtained from the Ordnance 
Survey Office, Dublin. The one-inch map for the 
16 sheets of the quarter-inch map only four appear 
to be published. There is a recent six-inch map of 
Dublin and surroundings. These maps are colour 
printed. 

Our Astronomical Column. 
VARIATIONS IN THE SPECTRUM OF 6? ORIONIS.— 
M. F. Henroteau directs attention (Comptes rendus, 
April 30, p. 1210) to the spectrum of the star @ 
Orionis, which is of magnitude 5°17 and situated in 
the nebula of Orion (R.A. 5" 30"°5, Dec. — 5° 29’, 1900), 
being of the B-type spectrum. In 1904 Prof. E. B. 
Frost discovered the star to be a spectroscopic 
double with a radial velocity of 140 km. In 1919 
and 1920 M. Henroteau found that in addition to the 
broad absorption lines of hydrogen and other elements, 
there were super-imposed on them thin bright lines 
which gave a velocity less than that accorded by 
Frost. To verify this, Otto Struve of the Yerkes 
Observatory obtained several spectrograms in 1922, 
but these showed no evidence of bright lines. How- 
ever, another spectrogram on March 2 of the present 
year displays these sharp bright lines. Thus we have 
a B-type star, not known as a variable, which inter- 
mittently presents bright lines, a phenomenon very | 
rare in occurrence. What adds great interest to this 
particular star is that it is situated in the nebulosity | 
of Orion, and this situation may account for the 
peculiarity. M. Henroteau proposes to make a 
special study of its spectrum. 
CoLouRS AND SPECTRA OF DouBLE StTArRs.—Till 
recently the course of a star’s evolution was con- 
sidered to be defined by the sequence represented by 
types O B AF G K M, and the fact that the fainter 
components of binaries are often bluer than the 
brighter components was a source of much per- 
plexity. One of the results of the “‘ Giant and 
Dwarf ’’ hypothesis was to afford a simple explana- 
tion of the observed facts, since among giants the 
blue stage is later than the red; and, conversely, 
the observed phenomena afford another strong argu- 
ment for that hypothesis. Mr. Peter Doig has traced 
the bearing of these facts in two papers during the 
past year; now Mr. F. C. Leonard returns to it in 
Lick Obs. Bull. No. 343. He has photographed the 
spectra of a number of close pairs with a one-prism 
spectrograph on the 36-inch refractor, finding it 
possible to get separate spectra even with 
only 1” apart; where the magnitudes differed the 
brighter star was occulted by a screen for part of 
the exposure. In order to classify the spectra he 
also took spectrograms of several typical stars with 
the same instrument, since he notes that slit spectro- 
grams differ systematically from the objective-prism 
series used at Harvard. 
The resulting spectral differences of the components 
of the binaries were then correlated with absolute 
NO. 2800, VOL. 111] 
pairs | 
magnitudes, and with differences of magnitude and 
mass, the facts being displayed in a series of dia- 
grams; he classifies stars not fainter than I.o mag. 
(absolute) as giants, the remainder as dwarfs; it is 
clearly shown that among giants the primary is 
redder, among dwarfs bluer. Once this law has been 
established it enables us to make estimates of the 
absolute magnitudes of stars of undetermined paral- 
lax. Further, the difference of spectral type in- 
| creases as a rule with increasing difference of ab- 
| solute magnitude or of mass, and there is hope that, 
by tabulating these differences in as many cases as 
possible, a clue will be obtained as to the relative 
duration of the stages of development corresponding 
to the various spectral types; such information 
| would be of much use in cosmogony. The research 
also affords a proof that the less massive stars pass 
| through their stages more rapidly than the massive 
ones ; this was indeed generally assumed, but it has 
been questioned. 
The cases of Sirius and o? Eridani are noted as 
| anomalous, the discordance in magnitude being much 
greater than we should expect from the disparity in 
mass; Mr. Leonard suggests that in the latter case 
the mass-ratio should be reinvestigated; that of 
Sirius cannot be much in error. 
THE RADIAL VELOCITIES OF 1013 STARS.—Messrs. 
W. S. Adams and A. H. Jay contribute to the April 
number (vol. 57, No. 3) of the Astrophysical Journal a 
catalogue of radial velocities which includes many of 
the results obtained in this line of work at the Mount 
Wilson Observatory during the past few years. The 
list is composed almost wholly of stars with spectra 
of types F, G, K, and M which have been observed 
| not only for radial velocity but also for determinations 
of absolute magnitude and spectroscopic parallax. 
The spectrograms have been obtained at the Casse- 
grain focus of the 60-inch and the 1oo-inch reflectors, 
and the latter instrument was employed chiefly for 
stars fainter than the eighth visual magnitude. 
Single prism spectrographs with prisms of 64° angle 
and cameras of 18-inch focal length were used. The 
faintest star photographed was of magnitude 99, and 
to to 15 stellar lines have been measured on each 
spectrogram, and a list of those most commonly 
employed is given in the paper. The results here 
collected have already been used to some extent by 
Stromberg, Seares, and the authors in investigations 
of space velocities and the relationship of velocity to 
absolute magnitude and mass, but their publication 
makes them now available to all. 
| 

whole country is available in 205 sheets. ‘Of the © 
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