Apri. 8, 1915] 
NATURE 
157 

gives the details of fourteen stars which have recently 
been found to have variable radial velocities, from 
plates taken by the D. O. Mills expedition to the 
southern hemisphere. The same author deduces the 
orbit of the spectroscopic binary v Centauri, giving the 
period as 137-939 days. This star is one of a group 
of Class B binaries, which have periods of about 130 
days. Mr. R. F. Sanford describes his investigation 
of the orbit of the spectroscopic binary e Volantis, a 
star of magnitude 4:5 and of Class Bs. The new 
elements show a period of 14:16833 days. A note by 
the same author on two spectrograms of the interest- 
ing irregular variable 7» Carinae indicates that the 
observations of 1913 and 1914 show no evidence of 
variation in radial velocity. 
Sorar Rapration Measures 1x Ecypr.—Bulletin Ne. 
14 of the HelwAn Observatory contains an account of 
some observations of solar radiation which have been 
carried out at the Helwan Observatory by Mr. 
Eckersley. It has been shown by Prof. Abbot that 
values of the ‘‘solar constant”? vary from day to day, 
and that even at two stations as far apart as Mount- 
Wilson (California) and Bassour (Algeria) there is a 
very well-marked correspondence between the values 
derived at these stations, so that the action of local 
atmospheric effects is not the cause of the fluctuations. 
Prof. Abbot considers the outstanding variation to be 
due to a real fluctuation of the solar constant. In 
order to investigate this question further, it was 
decided to make an extended series of observations at 
Helwan, and this was commenced at the beginning 
of last year. The account of these measures is given 
in this paper. For the statistical purpose of com- 
paring the results obtained with those at Mount 
Wilson, the highest precision of individual observa- 
tions is not required, but an extended series of 
measurements uniformly treated is of the greatest 
value. For this reason pyrheliometer measures of the 
total energy alone were made. The communication 
describes the method employed, the reduction of 
observations, and the results secured. While the value 
of the radiation derived from the Smithsonian Institu- 
tion observations at Mount Wilson is 1-932 (mean value 
of 696 observations taken at Washington, Mount 
Wilson, and Bassour during the period 1902-1912), 
the Helwan mean value derived is 1-782. The latter 
value is considerably less than the Smithsonian mean 
value, and the cause of the difference is dealt with by 
the author in subsequent paragraphs. Finally, 
evidence for the fluctuation during the period of 
observation is dealt with, and it is concluded that 
while some of the deviations are probably due to real 
fluctuation, no conclusive decision can be reached until 
the Mount Wilson results can be compared. 

THE BRILLIANT FIREBALL OF SUNDAY, 
MARCH 28. 
ETWEEN March 21 and 29 eight large meteors 
were observed, but by far the most brilliant 
object among them was that of March 28, 7.473 p.m. 
Its flight was witnessed by many hundreds of persons 
from the southern parts of England, as well as from 
the English Channel, France, and Belgium. 
As viewed from London, the meteor sailed slowly 
along a few degrees under the stars Sirius and Rigel, 
and further westwards to possibly beyond y Eridani. 
Mr. H. P. Hollis saw the meteor from a place about 
three miles due east of the Royal Observatory, and 
estimated its duration of flight as between five and 
six seconds. He did not see the beginning, and it 
was difficult to trace the exact point of extinction 
owing to trees behind which the object passed. 
Mr. G. P. B. Hallowes was in his observatory at 
NO.. 2371, VOL. 95] 


East Howes, Bournemouth, with an astronomical 
friend, Mr. C. Gregory, when the meteor burst out in 
the southern sky. It moved from the region of 
a Hydra to near Rigel at about the place of v Leporis. 
It passed a little above Sirius. Brilliancy far ex- 
ceeded Venus, and its duration was from three to 
four seconds. A trail 5° or 6° long followed the 
nucleus, and the latter burst into fragments at the 
end. The front of the head was yellow, the rear part 
red. Diameter, about 15’, or half that of the moon. 
Mr. A. King saw the meteor from Scunthrope, 
Lincolnshire, and from this northerly position its 
apparent path was very low, being from about 
117°—31° to g8°—32°. The brightness was estimated 
equal to Sirius, the colour yellow-green, and duration 
7x seconds. 
Mr. H. Rollason, of Montgomery, Wales, states 
that the meteor flamed out on the western sky, moving 
from S.E. to N.W., bursting twice, and enduring 
altogether five to six seconds. Many other observa- 
tions have been received or published in the daily 
papers. As usual, there are discordances, but it is 
not difficult to derive a real path fairly consistent with 
the data. 
The radiant point is indicated at 192°+ 4°, or pos- 
sibly 220°+14°, low in the eastern region of the sky. 
The height of the object was from about 71 to 23 miles 
along a path of 175 miles from over the neighbour- 
hood of Vire in France to the English Channel, about 
60 miles south of Eddystone. Velocity, 24 miles per 
second. The meteor seems to have been directed from 
a radiant comparatively unknown in March, but in 
April, contemporary with the Lyrids, there is a rich 
shower of slow and brilliant meteors from 200°+8° 
near o Virginis. 
The recent fireball must have passed almost vertically 
over Jersey, and from the Channel Islands and western 
parts of France it created a splendidly luminous effect. 
As viewed from Bournemouth the apparent size of the 
pear-shaped head of the meteor was considered to 
equal half the moon’s diameter, which, from the dis- 
tance of the object, would imply a magnitude of 
nearly two-thirds of a mile. This must have 
enormously exceeded the actual dimensions of the 
stony, or metallic, material composing the meteor. 
When undergoing combustion, the flame and expand- 
ing gaseous vapours from meteors give a_ vastly 
exaggerated idea of their real size. It must be very 
rare that a fireball exceeds one or two feet in the 
diameter of its material. 
I have ascribed a flight of 175 miles to the recent 
fireball, but it may have been much longer than that. 
Many of the observers did not detect the object until 
it had developed considerable brilliancy. The moon 
was nearing the full at the time of its appearance, 
but the meteoric visitor startled some of the spectators 
with its astonishing lustre. W. F. DENNING. 

TRE INS TILOLE, Ob Vib ieAles. 
\/CLUME XII. of the Journal of the Institute of 
Metals, representing the work of the Institute 
during the second half of 1914, has just appeared. 
This is one of the first -volumes of proceedings to 
appear since the outbreak of the war, and it indicates 
that the Institute of Metals has been able to pursue 
its activities, except for the fact that the autumn 
meeting which was to have taken place at 
Portsmouth early in September had to be aban- 
doned. An interesting series of papers, however, 
are fully discussed by correspondence in the Journal. 
One of the most interesting from the scientific point 
of view is the paper by Mr. O. F. Hudson on the 
critical point at 460° C. in zinc-copper alloys. Mr. 
