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NATURE 
[APRIL 28, 1923 

Dr. Epwarp P. Hype, who organised the Nela 
Research Laboratories in 1908, and for the past few 
years has occupied the position of director of research 
of the National Lamp Works of the General Electric 
Co., Cleveland, has tendered his resignation, to take 
effect on June 30. Dr. Hyde, who has been active 
in scientific and technical affairs for a number of 
years, has decided to take a prolonged rest abroad. 
He will temporarily discontinue many of his activities 
in scientific and engineering societies, but will retain 
the office of president of the International Commission 
on Illumination until its plenary meeting, to be held 
in the United States in 1924. 
Ix connexion with Dr.-Simpson’s Royal Institution 
discourse on “‘ The Water in the Atmosphere,” pub- 
lished in NATuRE of April 14, Prof. A. W. Bickerton 
writes to suggest an alternative formation for hail- 
stones which have the form of cones mounted on 
hemispherical bases. It is suggested that these may 
be formed by the freezing of raindrops which solidify 
first on the outside, then, as the core freezes, the 
expansive pressure bursts the spheres along the lines 
of minimum resistance, these being the lines of a 
pentagonal dodecahedron. The difficulty of this ex- 

made by Dr. Simpson, forms above the region where 
raindrops are met with. Also the “ stones ”’ of soft 
hail are frequently so large that the mass of twelve 
of them would be much greater than the mass of the 
largest possible raindrop— which has a diameter of 
less than half a centimetre. © 
THE Gifford Lectures delivered in 1922 by Prof. 
C. Lloyd Morgan will shortly be published by Messrs. 
Williams and Norgate under the title of ““ Emergent 
Evolution.””’ Among the chapter headings are the 
following :—emergence, mental and non-mental, rest 
latedness, reference, memory, images, towards reality, 
vision and contact, relativity, causation and causality, 
and evolutionary naturalism. : 
Messrs. SOTHERAN’S Catalogue of Science and 
Technology is always of bibliographic interest and 
value, being carefully classified, and containing in- 
formative annotations to many rare volumes offered 
for sale by the publishers of the catalogue. The 
latest part is No. 783, dealing with mathematics. 
It should be seen by all who take an interest in 
the subject. The catalogue is obtainable from H. 
planation is that soft hail, to which reference was ' Sotheran and Co., 140 Strand, W.C.2. 

Our Astronomical Column. 
THE PLANET JuPITER.—This planet will arrive at 
opposition to the sun on May 5, when its distance 
from the earth will be about 410 millions of miles. 
It is now visible during the whole night, and is 
favourably situated for telescopic examination. The 
Great Red Spot in the southern hemisphere remains 
faintly visible, and a slight increase in its rotation 
period has occurred in the last few years. Its present 
longitude is 228°, so that it precedes the zero meridian 
ot System II. by about 3 h. 38 m. Observations of 
the transits of this marking will be valuable, and may 
be witnessed at about the following times :— 
hm; h, m, 
April 29. 8 47 G.M.T. May 8.11 6G.M.T. 
May > If Lo! -2r i sr Dea mT = 
” Si SE. 59 ” uw, AS. Ory ” 
ia 6. 9 28 #8 33 LEG Ohne 5 
The extensive dusky marking, known as the south 
tropical disturbance, is now in contact with the 
following end of the Great Red Spot, and it will be 
interesting to watch this object, as it passes the Red 
Spot in ensuing months. 
From recent observations by Mr. F. Sargent of the 
Durham University Observatory, it appears that 
the rotation period of the south edge of the South 
Equatorial belt of Jupiter shows an abnormal period 
of 9" 52™ 37°. This latitude on Jupiter falls between 
the two well-known currents, on which Systems I. 
and II. were based, the periods being 9" 50™ 308 and 
gh 55™ 40-6 (Nautical Almanac, 1923, p. 568-71). 
The unusual time of rotation was derived from a 
mean of three markings, but the observations extended 
over too short an interval to obtain exact results. 
There is no doubt, however, that there is a1. inter- 
mediate current between that in which the Great 
Red Spot is situated and the equatorial markings, and 
it will be important to follow the objects seen by Mr. 
Sargent which on March 29 were in longitudes from 
309°7° to 325-1° (System I.). 
NO. 2791, VOL. 111] 

SPECTRA OF THREE O-TYPE StTars.—Dr. H. H. 
Plaskett contributes to the Publications of the 
Dominion Astrophysical Observatory (vol. 1, No. 30) 
an important research on the spectra of three O-type 
stars. These stars show enhanced line spectra 
which can only be reproduced terrestrially under 
extreme conditions of excitation. Their spectra thus 
afford an opportunity for testing theories on the 
origin of spectra and for ascertaining some of the 
physical conditions in stellar atmospheres. The 
stars in question were 1o Lacerte (Oe 5), 9 Sagittze 
(Oe 5) and B.D. 35° 3930 N (Oe) and their spectra 
were secured with the universal spectroscope at- 
tached to the 72-inch reflector using one-, two- and 
three-prism dispersion.” Dr, Plaskett first points out 
that if the Pickering lines (f Puppis) are due to 
enhanced helium, Bohr’s theory predicts the existence 
of enhanced helium components about 2A to the 
violet of the hydrogen lines. He then gives his 
evidence for showing that those predicted components 
are present in his spectra, which demonstrates that 
the Pickering lines and \ 4686 are due to enhanced 
helium. 
In two of the stars Dr. Plaskett employs the mean 
wave-lengths of the enhanced helium lines for the 
determination of the value of the Rydberg constant 
Nz for helium, and deduces the values of Planck’s 
constant and the mass and charge of the electron. 
Those values he compares with recomputed values 
from Paschen’s value of Nz and with results from 
other methods of determination. He deduces the 
temperatures of the O-type stars under discussion 
and gives the following values: 9 Sagitta, 18,500° K ; 
10 Lacerte, 15,000° K ; and B.D. 35° 3930 N, 22,000° 
K. He finally suggests a modification of the Harvard 
Classification of the O-type stars as follows : : 
Class Oo, Pickering lines disappeared; Class O5, 
(B.D. 35° 3930 N) ordinary helium disappeared ; 
Class O7 (9 Sagitte) Mg +, 4481 missing; Class Og, 
Si III +, pair 4552, 4567, on the point of appearing. 
a 
