234 
NATURE 
[JANUARY 7, 1904 
phenomena of recent years. The current issue contains 
many illustrations, among which are some good reproduc- 
tions of photographs and drawings of sun-spots, comets, and 
planetary features observed during 1903. The charts of the 
sky and the particulars of interesting phenomena, which are 
given for each month, will be found very useful by all who 
are engaged in practical astronomy. The ‘‘ Annuaire ’’ is 
published by M. Ernest Flammarion, 26 Rue Racine, Paris, 
at 1.50 francs (about 1s. 3d.). 
The card calendar issued by Mr. Arthur Mee, of 
Llanishen, under the title ‘‘ The Heavens at a Glance’’ 
* contains a very complete set of the tables and a great deal 
of the information required by an amateur practical 
astronomer. Being printed on a single stiff card, suitable 
for hanging on the observatory wall, it is exceedingly handy 
to use as a source of reference for current astronomical 
occurrences. Amongst other information the card contains 
a list of the principal meteor showers, with concise instruc- 
tions to observers, ephemerides of the planets and lists of 
double stars, variables and nebula. It may be obtained 
from Mr. Mee, at the above address, for 7d. post free. 
TuHE VaRIABLE STaR 1921, W AuriG#.—In No. 5, vol. 
xviii., of the Astrophysical Journal, Mr. J. A. Parkhurst, of 
the Yerkes Observatory, gives the details and results of a 
series of observations of the variable star W Auriga, made 
by him during the period December, 1898—March, 1903. He 
determined the position of the variable (for 1900) as 
R.A.=5sh. 20m. 8.6s., 5=+36° 48! 53”, and found that the 
magnitude varied from 9-3 at maximum to 13:5 at minimum. 
The strong colour of this variable is indicated by the fact 
that when the visual magnitude was 9-5 the photographic 
magnitude was only 10-9. 
The variations are best represented, according to the 
curves which Mr. Parkhurst has plotted from his observ- 
ations, by the following elements :— 
Max.=]J.D. 
24146484276 E. 
or December 
24, 1898+276 E., 
the interval, M-m, being 113 days. 
Licut Economy in Spectrum PuotoGRapny.—In a paper 
communicated to the current number of the Astrophysical 
Journal, Mr. J. A. Humphreys describes a number of 
arrangements used by him in photographing spectra for 
utilising to the full the light obtained from the light source 
under examination. He has found that the most generally 
convenient and effective arrangement, when terrestrial light 
sources are being used, is to place a spherical reflector 
behind the source so that the focus of the reflected light 
coincides with the origin. In this way both the reflected 
and direct light are utilised, and are together focused on 
the slit by an ordinary condenser. Comparison photo- 
graphs, which are reproduced in the article, show that the 
light reflected through the source suffers but little from 
absorption, and that the net result of using this arrangement 
is to obtain lines which would otherwise be too weak to 
photograph, and to strengthen the weaker lines. 
Another method, which may be used with any source 
when a grating is used as analyser, is to place a pair of 
inclined plane reflectors between the slit and the grating so 
that the rays from the top and bottom of the slit are reflected 
on to the centre of the grating, thereby condensing the light 
from the whole length of the slit into a narrower plane, and 
s) obtaining a stronger spectrum. In another, but some- 
what similar, form, the two plane reflectors are placed near 
to the photographic plate, so that the parallel rays from 
the top and. bottom of the grating are superimposed upon 
the rays from the centre. It is found that when long-focus 
gratings are used the slight lengthening of the path of the 
rays by reflection does not interfere, practically, with the 
definition. Many other arrangements, including the use of 
ellipsoidal and paraboloidal reflectors and cylindrical lenses, 
are explained and illustrated in Mr. Humphreys’s article. 
INTENSITY OF THE Sun’s Licut.—M. Ch. Fabry has com- 
municated to the Paris Academy of Sciences an interesting 
paper on the candle-power of the sun’s light at sea-level. 
By an ingenious arrangement, wherein the total solar light 
is diminished in a known ratio by passage through a slit 
and then through an ammoniacal solution of copper 
light of known candle-power, and, after various corrections, 
found that at sea-level, with the sun at the zenith, the solar 
light would be 100,000 times more intense than that pro- 
duced by a decimal candle at a distance of 1 metre, 
Supposing that the intensity of the light emitted by different 
parts of the apparent solar surface is the same, this result 
shows that the intensity of the light received—after atmo- 
spheric absorption—from 1 square mm. of the solar disc is- 
equivalent to 1800 candle-power, as compared with 150-200. 
candle-power per square mm. emitted by the positive pole 
of the electric arc. 
Taking the amount of heat received per minute from 
I square cm. of the solar surface as 1-5 calories, M. Fabry 
calculates that the energy consumed per candle-power is: 
about 0-12 watt, but, as the invisible heat rays suffer more 
by atmospheric absorption, the actual amount of energy . 
used up is probably between 0-15 and 0-2 watt per candle: 
(Comptes rendus, No. 23, vol. cxxxvii.). 
PRIZES PROPOSED BY THE PARIS ACADEMY — 
OF SCIENCES FOR 1904. 
HE following subjects for prizes are proposed for the 
year 1904 by the Paris Academy of Sciences :— 
In geometry, the grand prize for mathematical science 
(3000 francs), the subject proposed being to perfect, in some — 
important point, the study of the convergence of continued 
algebraical fractions; the Bordin prize (3000 francs), to de- 
velop and perfect the theory of surfaces applicable to the 
paraboloid of revolution; the Vaillant prize (4000 francs), to 
develop and study all displacements of an invariable figure 
in which different points of the figure describe spherical 
curves; the Francceur prize (1000 francs) and the Poncelet 
| prize (2000 francs), for discoveries useful to the progress of 
pure and applied mathematics. 
In mechanics, the extraordinary prize of 6000 frances, to 
recompense progress in the direction of increasing the 
efficiency of the French naval forces; a Montyon prize (700: 
francs), for the improvement or invention of instruments. 
useful to the progress of agriculture, or the mechanical arts. 
or sciences; and the Plumey prize (2500 francs), for an im- 
provement or invention relating to steam navigation. 
In astronomy, the Lalande prize (540 francs), for the most 
interesting observation or memoir dealing with astronomy ;. 
| the Valz prize (460 francs), for the most interesting observ- 
ation made during the current year ; and the Janssen prize, 
a gold medal, for an important work on physical astronomy. 
In geography and navigation, the Binoux prize (2000: 
frances), for a work dealing with either of these subjects. 
In physics, the Hébert prize (1000 francs), for the best — 
treatise or discovery useful in the practical application of 
electricity ; the Hughes prize (2500 francs), for work con=_ 
iributing to the progress of physics; and the Kastner- 
Boursault prize (2000 francs), for the application of elec- 
tricity to the arts, industry, or commerce. 
In statistics, a Montyon prize (500 francs), for the bes 
study in French statistics. 
In chemistry, the Jecker prize (10,000 francs), for work 
in organic chemistry. 
In physical geography, the Gay prize (1500 francs), for 
a study of the existing variations in the relative levels of 
land and sea, by means of precise observations, pursued 
over a fixed portion of the coasts of Europe or North’ 
America. 
In potany, the Desmaziéres prize (1600 francs), for a work 
on the cryptogams; the Montagne prize (1500 francs), for 
work on the anatomy, physiology, development or descrip-_ 
tion of the lower cryptogams; the de la Fons-Mélicocq 
prize (goo francs), for the best botanical work dealing with 
the north of France; and the Thore prize (200 francs), for 
the best work on the cellular cryptogams of Europe. 
In anatomy and zoology, the Savigny prize (1300 francs), 
for the assistance of young zoologists making a special study 
ot the invertebrates of Egypt and Syria; and the Thore prize 
(200 francs), for a work on the anatomy of a European 
species of insect. 
In medicine and surgery, a Montyon prize (three prizes of 
2500 francs, three mentions of 1500 francs), for discoveries 
useful in the art of healing ; the Barbier prize (2000 francs), 
sulphate, he compared the light with a constant standard | for a valuable discovery in the surgical, medical or pharma- 
NO. 1784, VOL. 69] 
