178 
NATURE 
photograph taken of it at Bothkamp on September 28 
records a tail 3°5° long. 
The comet is in a good position for observation in 
the evening, and its movement northwards will. make 
the conditions more favourable. It is at present 
passing through the constellations of Equuleus and 
Delphinus, but later will reach Vulpecula and Cygnus. 
In The Times of October 2 we read that Westphal’s 
comet is the fourth member of the Neptune group of 
comets that has been observed at a second apparition, 
the others being those of Halley, Olbers, and Pons. 
Two other members of the group appeared in 1846 
and 1847, and are expected back about 1921 and 
1927. Westphal’s comet has much the shortest period 
(61118 years) of any member of the group, its aphelion 
being at almost exactly the same distance from the 
sun as the orbit of Neptune. 
PHOTOGRAPHIC STUDY OF THE SOLAR PHOTOSPHERE.— 
In an abstract from the Annals of the Observatory of 
Zé6-sé (Tome iii., 1912), M. S. Chevalier, S.J., 
describes the results of his research on the solar photo- 
sphere as studied photographically. He first of all 
describes the early observations of the solar, surface 
by Sir W. Herschel, and rapidly surveys those who 
followed him, concluding with the photographic re- 
searches of M. Janssen at Meudon. M. Chevalier 
points out that on these latter photographs the famous 
granules observed by Secchi, Dawes, &c., were 
recorded. _ 
He then directs attention to the possibility of errors 
creeping in when photography is employed. Is the 
image recorded on the photographic plate necessarily 
a faithful representation of the object photographed ? 
M. Chevalier says it is not, and in the present in- 
vestigation he attempts to show that the réseau photo- 
sphérique discovered on Janssen’s clichés is not solar. 
The phenomenon, he says, is chiefly due to deviations 
undergone by the luminous rays refracted in an 
abnormal manner. This abnormal refraction takes 
place in the interior of the telescope, and more 
especially in the neighbourhood of the secondary 
magnifier. M. Chevalier accompanies his memoir 
with a series of fine reproductions from photographs 
of the solar surface which he has taken to demon- 
strate his views, and it is by an examination of these 
that his conclusions must be studied. 
Statistics OF NEBUL2 AND CLusTERS.—In the Arkiv 
for Matematik, Astronomi och Fysik (Band 9, 
No. 15), Prof. C. V. L. Charlier has published a pre- 
liminary paper on the statistics of nebule and 
clusters. This contribution is part of the work of the 
Lund Observatory, which has undertaken a discus- 
sion of the position of the nebulous stars in space, 
and these statistics form a preliminary part of the 
investigation. In this publication Prof. Charlier 
represents both in statistical and graphical form, the 
information collected on card catalogues of the co- 
ordinates, brightness, size, and form of nebula, as 
well as other observations of interest. The base of 
the card catalogues was the three great catalogues 
of Dreyer. In these pages the results are given pur- 
posely without any discussion regarding their bearing 
upon the question of the distribution of the nebulz 
in space. He remarks, however, that while in many 
respects they speak for themselves, in others con- 
clusions must be drawn with great caution. The main 
interest here are the relations between the Milky Way 
and the positions and numbers of the nebulez. 
When it is remembered that distinction is made 
between five different classes of nebulous objects, 
namely, clusters, globular clusters, planetary nebule, 
annular nebula, and nebula, and that the objects 
number 13,223, some idea of the work involved in 
the investigation will be gathered. 
NO. 2293, VOL. 92] 
the varied uses to which gas can be efficiently and — 
[OcToBER 9, 1913 _ 
SPECTROHELIOGRAPHIC RESULTS FROM Meupon. 
memoir by MM. H. Deslandres and L. d’Azambu 
appearing in No. 9 of the*Comptes rendus of t 
Paris Academy of Sciences, contains an interesting 
historical survey of the spectroheliographic work 
carried out at Meudon. The paper is more especially 
concerned with the qualitative results obtained by 
examination of the spectroheliograms secured since 
1g08, when the spectroheliograph of high dispersion 
was erected. Whilst careful to point out that the 
evidence does not permit the formulation of general 
laws, the authors are content to state that during the 
period in question the “filaments” (dark and definite 
stream-like markings seen in hydrogen and calcium 
light) have followed, but with a distinct lag, more 
pronounced in the case of the polar disturbances, 
the sun-spot variations. In this regard the polar dis- 
turbances recall the secondary maximum of high-— 
latitude prominences. On the other hand, the 
“alignments”? (markings somewhat less dark and 
sharp seen only in calcium light) have been without — 
noticeable variations. 7 
AN EXHIBITION OF PROGRESS IN LIGHT- 
ING AND HEATING BY COAL GAS. 
HE National Gas Exhibition at Shepherd’s Bush, — 
which will be open during the whole of October, 
affords the best object lesson in gas lighting that the 
public has ever had the opportunity of studying, and — 
the fascination is greatly increased by the absence of 
competing stalls, the exhibits being shown in model — 
rooms, shops, studios, &c., under all the conditions 
in which they are likely to be used in practice. 
It is something of an achievement to have induced 
the leading gas undertakings, municipal and private, 
and the leading manufacturers of gas appliances in 
the United Kingdom, to sink their individuality and — 
rivalry and to cooperate in a coherent exhibition of 
profitably applied. The result should be of benefit both 
to the industry and to the public generally. 
The exhibition impresses one with the enormous 
strides that have been made during the last few — 
years in the application of gas for manufacturing, — 
domestic, and public: purposes. The introduction of — 
vertical retorts, improved methods of purification, and 
the resulting greater yield of gas, coke, and by- 
products obtained from the coal carbonised, have — 
resulted in its price being kept down in spite of the 
gradual rise in the cost of coal, whilst the enormous 
progress that has been made in the methods em- 
ployed in its combustion has popularised it to an 
extent that could hardly have been foreseen a few 
years ago. 
There is not the least doubt but that the intro- 
duction of the atmospheric burner and the incandes- 
cent mantle has been the real factor which has made 
gas the most important fuel for both heating and 
lighting, and in the present exhibition the progress 
that has been made from the inception of the union 
jet by Nielson in 1820, which gave less than one candle 
per cubic foot of gas consumed, to the modern high- 
pressure incandescent burner, with its sixty candles 
per cubic foot of gas, is demonstrated in a striking 
manner. 
Various apparatus for raising gas to the pressure of 
several pounds per square inch, necessary in high- 
pressure lighting, is to be seen at work in the Indus- 
trial Hall, and the bearing which the high-pressure 
distribution has upon commercial applications is 
shown by the exhibition of a number of furnaces for a 
multiplicity of purposes, such as melting metals and 
hardening steel. In these cases it is necessary to 
concentrate the temperature over a defined area, and 
