Juty 8, 1915] 
NATURE 
519 


tunately optical activity is an exceptional attribute, 
and a method depending on solubility which has 
been described recently by Mr. N. V. Sidgwicl, in the 
Journal of the Chemical Society (vol. cvii., p. 672), 
promises to become applicable on a somewhat wider 
scale. The isomerism of the two forms of benzoyl- 
camphor has been confirmed by the new method, and 
similar phenomena have been detected in two addi- 
tional cases. Negative results indicate that in other 
cases the modifications may be due to polymorphism, 
but this conclusion can only be tentative, as identical 
results would be produced by rapid isomeric or poly- 
meric changes. 

OUR ASTRONOMICAL COLUMN. 
THE Mereor Season.—Mr. Denning writes :— 
“There is a special season for many things, and 
meteors have their more favourable times and periods. 
Astronomers generally regard the months of August 
and November as the particular dates when meteors 
are abundantly displayed. There is _ substantial 
ground for this idea. August and November are 
memorable as having been the months of occasional 
brilliant exhibitions of meteors in the modern past. 
In more ancient times July and October were the 
favoured months by the same meteoric systems, which 
have slowly advanced in their dates owing to changes 
in astronomical conditions. To the regular ob- 
server the meteoric season may be said to open at 
about the middle of July, when there occurs a decided 
increase in the visible number of meteors contem- 
porary with the first oncoming of the Great Perseid 
shower. We may usually observe twice as many 
meteors during the last half of July as in the first 
half. This is not wholly due to the activity of two 
or three special showers, but is partly attributable to 
a general increase in meteoric phenomena. July 
often affords a most agreeable recompense to the ob- 
server in supplying plenty of interesting objects, and 
this is always appreciated after their rarity in pre- 
ceding months. Thus in June, 1915, at Bristol, only 
thirty-six meteors were seen in watches of the sky 
extending over 203 hours, a degree of scarcity which 
I never remember to have previously experienced. 
The Perseids ought to be splendidly witnessed this 
year with suitable weather about August 9-13. The 
path of the larger meteors should be carefully re- 
corded, also the time when the maximum number of 
meteors is visible.” 
DISPLACEMENTS OF ENHANCED [RON LINES at CENTRE 
OF THE SuNn’s Disc.—The general displacement of the 
solar lines towards the red has been interpreted at 
the Kodaikanal Observatory as due to movements of 
the solar gases in the line of sight and not to pressure ; 
the movement is one of recession from the earth or a 
falling movement at the centre of the sun’s disc. Thus 
a circulation of the solar gases is suggested, the cooler 
gases falling and being replaced by the hotter gases 
ascending from below; such a circulation might 
account for the relatively great intensity of the en- 
hanced lines of iron and other substances in eclipse 
spectra as compared with their intensities in the 
Frauenhofer spectrum. With a view to detect the 
rising movement of the hotter gases, Dr. Evershed 
and Naragana Ayyar (Kodaikanal Observatory Bulle- 
tin 46) have made a special study of the enhanced 
lines of iron in the sun and in the electric arc, the 
results of which they now publish. Details are given 
as to the spectrograph employed, method of producing 
the enhanced lines, times of exposure, etc., and a table 
is published showing the shifts of enhanced lines at 
NO. 2384, VOL. 95| 

the centre of the sun’s disc. The list gives the results 
for sixteen lines which are of sufficient intensity for 
accurate measurement, and in every case except one 
these enhanced lines give positive shifts, showing that 
they cannot represent ascending gases as was sup- 
posed. Investigating the possibility of any relative 
shift between the enhanced and ordinary lines they 
find that there is none. Then they conclude ‘‘ that the 
enhanced lines of iron in the sun give therefore no 
evidence of a radial circulation of the solar gases nor 
of any relative movement compared with the arc 
lines.” 
THe Maximum BricHtTNess oF VENus.—M. Henry 
Rey describes in the June number of L’Astronomie 
some measures that he made with M. Comas Sola on 
the comparative brightness of Venus and _ Sirius. 
Taking advantage of a particularly clear evening at 
Barcelona on March 25 in 1913, when the planet 
Venus was at her period of maximum brightness, they 
secured a series of photographs of the planet and 
Sirius (out of focus) on the same photographic plate. 
In the case of the latter the size of the image was so 
adjusted as to be equal to that of the planet. The 
durations of the exposures were 2, 4, 6, 8, and 
ro seconds for the planet, and 25 seconds 1, 2, 
3, 4, 5 minutes for the star. A  compari- 
son of the discs led to the conclusion that 
10 seconds on Venus equalled two minutes on Sirius, 
or that Venus was twelve times brighter than Sirius. 
Thus the magnitude of Venus would be 6-72, Sirius 
being —1-4. Another communication on the same 
subject, by M. Salvador Raurich, appears in the same 
journal, and gives the brightness of Venus as nine 
times that of Sirius, nineteen to twenty times that of 
Aldebaran, and five times that of Jupiter. 
CauSES OF CHANGES IN THE Rate oF A WatcH.— 
There are no doubt many amateur astronomers who 
depend for their time on watches, and now that wire- 
less time-signals cannot be received, they have to trust 
to their rates for longer periods than was then neces- 
sary. When such watches are taken out of the pocket 
and hung up or placed on a rest for the night the 
change in the rate is liable to many vicissitudes. Such 
variations can amount to a considerable quantity, and 
an interesting note on this subject appears in the 
May number of the Monthly Notices of the Royal 
Astronomical Society, by Mr. J. J. Shaw. In his con- 
cluding remarks the author states that ‘singe writing 
the foregoing, it has been brought to my knowledge 
that the late Lord Kelvin made some similar experi- 
ments with watches,” particulars of which were given 
in his ‘‘ Popular Lectures,’’ vol. ii., p. 360. The sub- 
ject is, nevertheless, of such practical importance that 
attention may be directed to Mr. Shaw’s communica- 
tion. The chief moral to be drawn is, do not hang 
your watch up on a hook or nail unless precautions 
are taken to prevent the watch from oscillating. If 
you do, then an oscillation may be set up, under the 
influence of the watch’s own balance-wheel, which 
will change the rate from a fraction of a second a 
day to one of many seconds or even to a quarter or 
more of a minute. 

THE BRITISH SCIENCE GUILD. 
HE ninth annual meeting of the British Science 
Guild was held on Thursday, July 1, the chair 
being taken by the president, the Right Hon. Sir 
William Mather. In opening the proceedings, the 
president expressed regret that owing to weak health 
Sir Norman Lockyer, chairman of the Executive Com- 
mittee, and the founder of the guild, was unable to be 
present. Referring to the presidential address to the 
