Marcu 24, 1904] 
NATURE 
503 
The following refractive indices for vitreous silica are re- 
corded in the paper :— 
Wave-length | 
Index Wave-length Index 
7950 (Rb) | 17453398 | 2748°68 (Cd)... | 1°496131 
A’7682°45 (Ka) | 1°4538915 | 2573°12 4, -.. | 1°593707 
B’ 7065°59 (He)! 1°455180 | 2445°86 (Ag) | 1751096 
C 6563704 (Ha)...) 1°4564147 | 2312795 (Cd) 1°519373 
D 5893°17 (Na)...) 14584772 | 226513 ,, ... | 1°523053 
A 5607°1 (Pb).... 1°459507 ZIQAAL 55. 1°529103 
E 527011 (Fe) ...| 1°4609945 | 2144745 ,,°... | 1°533898 
F 4861°49 (Hg).... 1°463165 2098°8 (Zn).. 1°538547 
G’ 4340°66 (Hy)...| 1°4668500 | 2062°0_ ,, 1°54271 
H’ 3961°68 (Al).... 1°470542 2024e2 ,,°... | 1:54721 
3610°66 (Cd)... 1°475112 1988°1 (Al) 1°551990 
3302°85 (Zn)... 1°480610 19335 5,7... | 1°55998 
3034°21 (Sn)...| 1°486881 18522 5 1°5743 
Temperature Refraction coefficient for D for 1° C. — 000000346. 
Note.—The number of figures in each index indicate the estimated 
freedom from errors of observation. The following interpolated indices 
{see focal curves) are in all probability more correct for the wave-lengths 
given:— 
1 1°45516. 2 1°53392- 3 1754728. 4 1*56003. 
Royal Astronomical Society, March 11.—Prof. H. H. 
Turner, president, in the chair.—The secretary gave a short 
account of a paper by Prof. Ernest W. Brown on the degree 
of accuracy of the new lunar theory, and on the final values 
of the mean motions of the perigee and node.—An account 
was also given of a paper by Mr. E. Nevill on the com- 
parison between the purely theoretical and observed places 
of the moon, containing some criticisms of Mr. Cowell’s 
note on the errors of the moon’s tabular longitude pub- 
lished in the November number of the Monthly Notices.— 
Prof. Turner read a note on the instrumental errors affect- 
ing observations of the moon, in which he concluded that 
it seems probable that meridian instruments may give very 
different values for the parallactic inequality, and that 
the results derived by Mr. Cowell, especially that for the 
sun’s parallax, must, until these instrumental errors have 
been more fully discussed, be received with -aution.—Mr. 
Cowell read a paper on methods of analysis of the moon’s 
errors, with some results.—The Astronumer Royal de- 
scribed the volume of the Greenwich Astrographic Cata- 
logue, now in course of publication. The determination of 
positions and magnitudes of the stars was discussed, and 
the probable errors of photographic star places compared 
with those obtained from meridian observations.—Mr. 
Furner read a paper by Mr. Storey and himself on the 
absolute proper motions of certain double stars showing 
large relative motion.—Mr. Maunder read a paper by Mrs. 
Maunder and himself on the date of the passage of the 
vernal equinox from Taurus into Aries, illustrated by 
photographs of Babylonian tablets.—Other papers were 
taken as read. 
Royal Meteorological Society, March 16.—Captain D. 
Wilson-Barker, president, in the chair.—Mr. Richard H. 
Curtis delivered a lecture on water-vapour. 
Paris. 
Academy of Sciences, March 14.—M. Mascart in the 
chair.—On the solubility of silicon in zinc and lead: Henri 
Moissan and F. Siemens. Silicon commences to dis- 
solve in zinc at a temperature of about 550° C., and at 
850° C. the molten metal contains about 1-62 per cent. of 
silicon. As the temperature increases the solubility in- 
creases very rapidly. Silicon commences to dissolve in lead 
at a much higher temperature than in zinc, about 1100° C., 
and only 0-79 per cent. is dissolved at the boiling point of 
the lead. The results are expressed in the form of curves. 
—On a new mode of formation of calcium carbide: Henri 
Moissan. By the electrolysis of fused calcium chloride, or 
better, of a mixture of fused calcium fluoride and chloride, 
in a graphite crucible, the metallic calcium formed combines 
NO. 1795, VOL. 69 | 
partially with the carbon, forming calcium carbide. The 
yield is poor, but the observation is interesting, since the 
carbide is formed in this reaction at a temperature as low 
as 650° C.—Observations concerning the mode of fructifi- 
cation of the Cycadofilicinez : R. Zeiller. A discussion of 
the bearing of some recent work by R. Kidston on the 
views of M. Grand’Eury. It is pointed out that the gymno- 
sperms held a much more important place in the formation 
of the Coal-measures than has hitherto been supposed.— 
The comparative actions of heat and the mn-rays on 
phosphorescence: R. Blondlot. It is known that a rise of 
temperature increases the intensity of phosphorescence of 
a faintly luminous screen, but a comparison of this effect 
with that of the n-rays on a similar screen shows important 
differences. Thus, whilst the n-rays increase the quantity 
of light emitted normally by the screen, they diminish the 
amount emitted obliquely. The effect of heat, on the other 
hand, is to increase the light emitted in all directions. An 
experiment is described by means of which the two effects 
can be compared on the same screen.—On the paludian 
character of the plants which form combustible fossils of 
all ages: M. Grand’Eury.—Note by M. Bertin accompany- 
ing the presentation of an Italian marine atlas published 
by M. Corazzinii—On an experiment made by the Suez 
Company for the suppression of malaria by the destruction 
of mosquitoes : Prince d’Arenberg. By the adoption of the 
preventive measures indicated by Ross and Laveran the 
mosquitoes in the Ismailia district have been practically de- 
stroyed. As a consequence, a very marked diminution in 
the number of cases of malaria has resulted.—M. Volterra 
was elected a correspondant in the section of geometry in 
the place of M. Cremona, M. Brégger a correspondant in 
the section of mineralogy in the place of M. Carl von Zittel, 
and M. Flahault a correspondant in the section of botany 
in the place of M. Millardet.—On perfect ensembles and 
uniform functions: M. Zoretti.—On the optical measure- 
ment of the difference between two thicknesses: A. Perot 
and Ch. Fabry.—New laws relating to the anomalous 
propagation of light in optical instruments: G. Sagnac. 
—On the amount of energy set free in a receiving antenna 
at different distances: C. Tissot. By modifying the method 
described in a previous paper, the author has been able to 
obtain a bolometer giving a much higher sensitiveness as 
a detector of the Hertzian waves. A comparison of the 
energy received at different distances showed that this prob- 
ably varies as the inverse square of the distance of the 
receiver from the sending station.—On the disappearance 
of the radio-activity induced by radium on solid bodies: 
P. Curie and J. Danne. The intensity of the induced 
radiation can be expressed as a function of the time as a 
difference of two exponentials. These results can be ex- 
plained theoretically by adopting the views of Rutherford, 
who supposes that the emanation, acting on the solid walls, 
creates a radio-active substance which disappears according 
to a simple exponential law. In disappearing this gives 
rise to a new radio-active substance, also following a simple 
exponential law, with a different coefficient.—On the natural 
rotatory power of certain bodies for the n-rays: H. Bagard. 
The rotatory power of solutions of sugar, tartaric acid, and 
of turpentine for eight groups of n-rays has been examined, 
the rays being distinguished by their refractive indices 
through aluminium and by their wave-length (Blondlot). 
For turpentine and sugar, the rotations are in the same 
sense as with ordinary light, and are normal in that the 
rotation varies in the inverse sense with the wave-length. 
For tartaric acid, which produces a dextro-rotation with 
ordinary light, the rotation is to the left with the n-rays. 
The rotations observed with the latter are several hundred 
times greater than with ordinary light; thus a solution 
giving +4° 42/ in a column of 20 cm. length with ordinary 
light gave —138° with n-rays in a column only 0055 cm. 
long. It was found that the rotations produced were pro- 
portional to the thickness of the solution within the limits 
of experimental error.—Bishop’s circle for 1902-1904: 
F, A. Forel.—Simple demonstration of the phase rule: 
A. Ponsot.—On an apparatus designed to act as a regulator 
for a water pump: J. Meunier.—The action of carbonic 
acid upon solutions of sodium nitrite: C. Marie and k. 
Marquis. Fresh experiments are adduced in support of 
the view that nitrous acid is set free from nitrites by the 
