288 
even when the light is approximately monochromatic. By 
Fourier’s theorem of double integrals 
he) = I (Ccos wt + S sin zt) tv, 
where 
+0 +n 
rif : 
G=2 [fe coswudv, S = — | A) sin wwe. 
| TT | 
mes x 
This is true provided /(/) is subject to certain conditions, which 
are proved to be present in any physical problem. The object 
of the paper is to inquire whether the above theorem justifies 
us in regarding any plane-polarised plane light motion as equiva- 
lent to acombination of simple harmonic vibrations, with periods 
varying from oto”. The element of the integral suggests a 
vibration of amplitude da /C? + S2, phase tan 2S and period 
on : ; ¢ : 
—, Itis proved that in certain very general cases such an in- 
ue 
lerpretation is possible, notably in the case of ‘* constant” light, 
such as presents a steady appearance. 
This calculus enables us to discuss the width of the lines in 
the spectrum of an incandescent gas, taking into account not only 
the velocities of the molecules, but also the effect of collisions, 
and of radiative damping in the molecular vibrations. The con- 
nection between Rontgen rays and ordinary light is examined, J. 
J. Thomson’s theory of the former being assumed. It is shown 
hat perhaps ;j'5a of the energy of the rays will be in the visible 
spectrum. The theory of dispersion is considered with reference 
tonatural light as opposed to a simple harmonic train of waves. 
Paris. 
Academy of Sciences, July 10.—M. van Tieghem in the 
chair.—The Perpetual Secretary announced to the Academy the 
loss it had sustained by the death of Sir William Flower, Corre- 
spondent in the Section of Anatomy and Zoology.—Remarks by 
M. Ed. Perrier on his Zyazté de Zoologze.—New researches on 
argon and its combinations, by M. Berthelot. Having a larger 
quantity of argon placed at his disposal, the author has repeated 
his earlier observations on the reactions between argon and cer- 
tain organic compounds. Entirely negative results were obtained 
when mixtures of argon with ethylene, glycollic ether, aldehyde, 
acetone, amylene, petroleum ether, propionitrile, allyl sulpho- 
cyanide, or amylamine were submitted to the prolonged action 
of the silent discharge, the original volume of argon being re- 
covered unchanged. With benzene, toluene, cymol, turpentine, 
anisol, phenol, benzaldehyde, aniline, phenyl sulphocyanide, 
and benzonitrile, on the other hand, an absorption of argon took 
place inamounts varying from one to six per cent. At the same 
time a greenish fluorescence appeared, giving a characteristic 
spectrum.—On the geographical and cartographical work carried 
out in Madagascar by order of General Gallieni between 1897 
and 1899, by M. Alfred Grandidier. The values previously 
assumed for the latitude and longitude of Tamatave, Andé- 
vorante, Fort Dauphin, and other towns in Madagascar are here 
revised, and the differences tabulated. —On the dialkylbenzoyl- 
benzoic acids and their tetra-chlor-derivatives, by MM. A. 
Haller and H. Umbgrove. Details are given of the prepar- 
ation and properties of tetrachlordimethylamidobenzoyl- 
benzoic acid, acetyldimethylamidobenzoyltetrachlorbenzoic 
anhydride and the corresponding ethyl and _ methyl 
ethers, dimethylamidobenzoyltetrachlorbenzoic acid and 
the anhydride of acetyldiethylamidobenzoyltetrachlorbenzoic 
acid, together with its ethyl and methyl ethers.—On the de- 
velopment of analytical functions of several variables, by M. 
Paul Painlevé.—Contribution to the theory of musical instru- 
ments, by M. Firmin Larroque.— Remarks on the use of cryo- 
hydrates, by M. A. Ponsot.—Action of nitric oxide upon chrom- 
ous salts, by M. Chesnau. Chromous salts in solution dissolve 
nitric oxide like ferrous salts, giving only one compound. On 
heating, or placing in a vacuum, this compound gives off no 
gas, thus differing from the corresponding ferrous compound. — 
On metallic sulphantimonites, by M. Pouget. Solutions of 
potassium sulphantimonites by double decomposition with salts 
of metals may give salts of the types SbS,M3, or SbS;M.K, but 
in no case of the type SbS,MK,.—Action of phenylhydrazine 
upon alcoholic bromides, chlorides, and iodides, by M. J. 
Allain Le Canu. The iodides behave differently to the cor- 
NO. 1551, VOL. 60] 
NATURE 
[Jury 20, 1899 
responding bromides and chlorides in respect to their reaction 
with phenylhydrazine —On the aminocampholenes, by MM. 
E. E. Blaise and G. Blanc.—Contribution to the study of an 
oxyptomaine, by M. Cichsner de Coninck. The oxyptomaine 
C,H,,NO was prepared by the action of hydrogen peroxide upon 
the pyridic ptomaine, CgH,,N. In the present paper details 
are given of its bromohydrate, chloroaurate, and chloromercurate. 
—New method for the acidimetric estimation of alkaloids, by 
M. Elie Faliéres. The titration is conducted with an am- 
moniacal copper solution instead of litmus or one of the 
ordinary indicators. The experimental results were very satis- 
factory.—On_ benzoyl]-furfurane, by M. R. Marquis. Benzoyl- 
furfurane is readily obtained by the interaction of pyromucyl 
chloride and benzene in presence of aluminium chloride. —The 
egols, new general antiseptics, by M. E. Gautrelet. Parasulphones 
derived from phenols are nitrated, and the ortho-nitro-phenol- 
parasulphonate of mercury and potassium prepared from this. 
The compounds thus obtained are termed egols, phenegol from 
phenol, cresegol from cresol, and so on, and possess certain 
advantages as antiseptic agents.—The 7d/e of heat in muscle 
action, by M. Raphael Dubois. —New observations on echidnase, 
by M. C. Phisalix. This ferment is present in snake poison, 
and is found to exert a di:static action not only upon anima} 
tissues, but even upon the active principle of snake poison, 
echidnotoxin. —Analogies between cultures of the vegetable 
fungus Mectrza and the parasitic fungus in human cancer, by 
M. Bra.—On the absence of regeneration of the posterior mem- 
bers of the leaping Orthoptera and its probable causes, by M. 
Edmond Bordage.—On the affinities of AZzcrosporum, by MM. 
L. Matruchot and Ch. Dassonville.—On the cicatrisation of 
the fascicular system, and of the secretory apparatus on the 
falling of the leaf, by M. A. Tison.—Barometric deviations on 
the meridian of the sun at successive days of the synodic 
revolution, by M. A. Poincaré.—On the use of self-recording 
meteorological apparatus in captive balloon ascents, by M. 
Léon Teisserenc de Bort. 
CONTENTS. 
Prestwich and Practical Geology . Oe oe 
Meteorology, Old and New. By W. E. P. Bieta 62462 
Machines for the Liquefaction of Gases . ae 
A Manual of Anthropology. ........... 269 
Our Book Shelf :— 
Ladd: ‘‘A Theory of Reality."—H. W. B. .. . 270 
“Great and Small Game of Africa.”—R. L. . 
Adie : ‘‘ An Introduction to the Carbon Compounds.” 
—A.' Hi... Aes ks ey 
Letter to the Editor:— 
On the Deduction of Increase-Rates from Physical 
and other Tables.—Prof. J. D. Everett, F.R.S. 271 
The Penycuik — (Lilustrated.) By F. 
A. D. 56.6 6 CLO oS AS 
Pioneer Cimber! Gaenreted!) By, Profi@ivGa 
Bonney, F.R.S., °c eee 274 
Bower-Birds. ([iustrated.} By R. L. ie : 275 
The Cosmic Origin of Moldavite. (///ustrated.) . 276 
Notes ofa 277 
Our AGironomicall Cotten: -- 
Tempel’s Comet 1899 ¢ (1873 II.) . 28 
Holmes’ Comet 1899 a (1892 III.) 281 
Dynamical Theory of Nebulz 281 
The Natal Observatory : F 281 
Temperature Changes in Yerkes (object: was 3 281 
The Reason for the Hissing of the Electric Arc. 
(Lilustrated.) By Mrs.W. E. Ayrton . pee, 282 
Hybridisation. By Dr. Maxwell T. Masters, 
eR SS. 3 aie . ee 286 
University and watcaneeal fretellizence 287 
Scientific Serial | 5 5m > ORS os oo kg 
Societies and Academies . 287 
