144 
found, viz. 34°23 for sodium, and 14°17 for potassium, The 
two metals, mixed in the ratio of their equivalents, gave an 
alloy which is liquid at ordinary temperature, and which, 
on account of its brilliant metallic surface, might be easily 
taken for mercury ; onlyits greater specific gravity distinguishes 
the latter at once from the potassium-sodium alloy. This 
solidifies at about 4°°5 C., and iis capillary constant is 17°86. Very 
careful experiments were made for determination of the co- 
efficients of expansion, and their relation to the temperature, in 
suitable dilatometers. The linear expansions, deduced from the 
volume-expansions, were, for sodium, 0°c00853, and for potas- 
sium, 0°000721 ; pretty similar values were had in direct measure- 
ment of longitudinal expansion in a metal block. This 
coefficient of linear expansion exceeds that of all other metals, 
and is about three times the linear expansion of lead.—Prof. 
Helmholtz then gave a report of this year’s International Con- 
gress in Paris, from which he had just returned. The Congress 
having last year come to an understanding on the units occurring in 
electrical science and ‘‘technic,” and their designations, the 
point now was to determine those units exactly, so that practical 
normal units might be prepared. Attention was first given to the 
determination of the unit of resistance,—the “ ohm”? (as most 
easily practicable) ; that is, the exact measurement in metres of 
the column of pure mercury of one square milimetre cross-sec- 
tion at o° C., the resistance of which is the ‘‘ohm.” There 
were already quite a number cf measurements by methods 
which Herr Helmholtz specified in his lecture. The values ob- 
tained are: Herr Kohlrausch, 170593; Lord Rayleigh, by the 
British Association method, 1°0624; Lord Rayleigh, by 
Lorenz’s method, 1'0620; Mr. Glazebrook, in Cambridge, 
10624; Herr H. Weber, in Brunswick, 1'0611; Herren W. 
Weber and Zollner, 170552 ; Mr. Rowland, in America, 1°0572 ; 
Herr Dohrn, 170546. Against these pretty concordant values, 
however, stood the mean value obtained by Herr F. Weber, of 
Ziirich, by reliable methods, and from experiments agrecing 
well together, viz. 1°0471, which came so near the older ohm 
of the British Association, that the Congress, on the motion of 
Sir William Thomson, refrained meanwhile from forming a 
definite conclusion. It was rather agreed to recommend the 
experimenters (1) to compare their resistances with the standard 
of resistance which the French Government will produce; (2) 
to compare the induction coils by the method adopted by Herr 
Kohlrausch with the wire-circuit ; (3) in their measurements to 
avail themselves of the modified and still further to be improved 
method of Lorenz. The respective governments should finally 
be urged to support, as much as possible, the national experi- 
ments for determination of the ‘‘ ohm.” 
Paris 
Academy of Sciences, November 27.—M. Jamin in the 
chair.—The following papers were read:—Observations of 
small planets with the great meridian instrument of Paris Ob- 
servatory during the third quarter of 1882, by M. Mouchez.— 
Note on the verification and the use of the magnetic maps of 
Col. Al. de Tillo, by M. Lalanne. He compares magnetic ob- 
servations (of declination) made by him in 1837, in four localities 
of the region north of the Sea of Azof, with Col. de Tillo’s 
two maps (for Russia), and notes some defects of the latter (the 
longitudes of the two do not refer to the same meridian, &c.).— 
Reply to the objections of M. Decharme to my rational concep- 
tion of the nature of electricity ; proofs of the validity of hypo- 
theses serving as the basis of this conception, by M. Ledieu.— 
General law of congelation of solvents, by M. Raoult. Every 
substance, dissolved in a definite liquid compound capable of 
solidifying, lowers its freezing-point. Inall liquids, the molecular 
lowerings of congelation with different compounds, approach 
two values invariable for each liquid, and one of which is double, 
the other (the greater being normal). The normal lowering 
varies with the nature of the solvent. A molecule of any com- 
pound, dissolvingin roomol. of any liquid, of different nature, 
lowers the freezing-point of the latter a quantity nearly constant, 
and near 0°°62.—Chemical study on maize at different epochs 
of its vegetation, by M. Leplay. Sugar is found in the leaves, 
and accumulates in the ste till the moment of formation of 
starch in the grains, It then migrates into the spike, first into 
the support of the grains, then into the grains themselves, where 
it is replaced by starch. This migration continues to be fed by 
the leaves till they disappear, then in great part by the stem— 
diminishing, however, as the starch is developed. The function 
of the sugar, then, is to furnish to the grain the elements of 
NATURE 
[ Dec. 7, 1882 
starch —On the conservation of solar energy ; reply to M. Hirn’s 
note, by Dr. C. W. Siemens. He estimates the temperature of 
the photosphere as 3000°, not too high to satisfy the conditions 
of combustion (M. Hirn’s estimate is 20,000°). The theory of 
diminution of light intensity as the square of the distance seems 
to be not applicable to the whole of the light of stars. Some 
wave-lengths less favourable to decomposition, may on this ac- 
count reach further. As to mechanical resistance of gaseous 
matter to the planets, he shows reason for thinking it much less 
than hitherto supposed.—On a theorem of M. Tisserand, by M. 
Stieltjes. —Extension of the problem of Remann to hyper-geo- 
metric functions of two variables, by M. Goursat.—On a new 
integrometer, by M. Abdank-Abkanowicz. Increased accuracy 
is obtained by means of a disc which rolls on a cylinder without 
slipping.—On a mode of transformation of figures in space, by 
M. Vaneeck.—Equilibrium of elasticity of a solid limited by a 
plane, by M. Boussinesq.—Theoretic interpretation of the 
calming effect produced by a thin layer of oil spread on 
the surface of the sea, by M. Van der Mensbrugeshe.—On 
electric motors, by M. Deprez. He describes an experiment 
proving that the two laws—that of independence of the 
current’s mechanical action, of the state of rest or motion 
of the ring, and that of proportionality of the electromotive 
forces to the velocities (supposing, of course, the intensity of the 
current constant)—hold good within very wide practical limits,— 
General expressions of the absolute :emperature, and of Carnot’s 
function, by M. Lippmann.—Range of sounds in air, by M. 
Allard. Experiments with different instruments yielded the 
result that ‘the intensity of sound in air decreases much more 
rapidly than according to the law of the square of the dis- 
tance. The second cause of enfeeblement is considered to 
lie in the non-homogeneous character of the air. A given 
sound may have, apart from the influence of wind, very different 
ranges, varying, ¢.g. from two to twenty nautical miles. For 
small augmentations of range the work required increases very 
rapidly. The differences cf range for different pitches within 
the octave are little sensible —On the reform of some processes 
of analysis used in laboratories of agricultural stations and ob- 
servatories of chemical meteorology (fourth memoir) ; volu- 
metric determination of alkalino-earthy carbonates in waters, by 
M. Houzeau.—Modifications of structure of nerve tubes in passing 
from the spinal roots into the spinal cord, by M. Ranvier.—On 
the present flood of the Seine, by MM. Lemoine and de 
Préaudeau.—Magnetic perturbations from November II to 21, 
1882, by M. Renou.—A letter from M. Tarry on the aurora 
showed that while the magnetic currents of earth lines render 
possible a pre-vision of aurora several hours in advance, those on 
submarine lines give a pre-vision of several days in advance. ; 
CONTENTS Phen 
RecENT RESEARCHES IN THE METAMORPHISM OF Rocks. By Dr. 
ARGH, GEIKIE; RARISS 3) 3) ad cr le =) jo) eis (ole gis atc 
HuMAN MorPHOLOGY = . 2 >. - 3 6 1) ml es Pe er bes! 
Our Boox SHELF:— 
Wood's ‘‘Common British Insects”? . . . = AL ee eet 
Ratzel’s ‘‘ Anthropo-Geographie oder Grundziige der Anwendung der 
Erdkunde auf die Geschichte ”’ SOME tei cs OS 
LETTERS TO THE EprroR:— 
Mimicry in Moths.—The DyKE OF ARGYLL . . eo wo eS 
Double F owers.—Dr. Maxwett T MasTeRS . . .. .. - 126 
Fruit of Opuntia.—Dr. Maxwett T. Masters _. . .. . . 126 
Hawk Moth Larva.—Surgeon-Major E. R. Jounson (With 
Tilustyatony at pier erence Peon nS 
The Fertilisation'of Common Speedwell.—A. MACKENZIESTAPLEY 127 
Wartmann’s Rheolyzer.— ERNST VON FLEISCHE. . - . . . . 127 
Pollution of the Atmosphere.—H. A. PHILLIPS . . . . . . - 127 
A Modern Rip Van Winkle.—SatTBuRN aia Jay fe cel, Feeney! 
Gootpen’s SimPce Dir-Circie (With Illustration). . . . . » « 128 
Tue Comet. By Witttam CrawForp WiNLocK, Assistant Astro- 
nomer, U.S. Naval Observatory; Dr. W. Doperck (With 
Télustrationsyo 4. te. ee) Oe Pree 
FUNCTION OF THE MEMBRANA FLACCIDA OF THE TyMPANiC MEM- 
BRANE. By JoHNM.CroMBIE . . - - + + + + = + + + + 329 
WEIGHTS AND MkASUREs . . 131 
ON THE Prorosep FortH Brivcs, By SirG. B Airy, ERS 131 
Nowpes Gee pa ke Mat ieee oe &, ede  beave oo RE ARSE o ega 
Tue-Royat Society. Anniversary Address by Dr. W1Lt1Am SpoTtis- 
WOODE, Eres. R-Sal eu) ee asp ns Se eet ct! 
M. MikLuKHo-MaAcLay ON New GUINEA. . - - «© = = «©. + 137 
Tue Aurora. By Admiral Erasmus Ommannay, F.RS.; Prof. 
Taccuint; J. RAND Capron; W. M. Fiinpers Petrie; H. DENNIS 
Tayror; Epwarp Pottock; J. Francis Cote; ALFRED BaTson; J. 
Ranp Capron: F. R. CrapHam; Tuos. Wm. BackHouse; Prof. 
L. G. CARPENTER (With Diagrams) . . » - «+ + + + + + 138 
ONIVERSITY AND EDUCATIONALINTELLIGENCE . «© «© «© + + «© + 42 
ScIENTTIFIC/SERIALS#. ene ens) sneer se) = Sip celasighe mma 
SocigTIES AND ACADEMIES +» + + « - i De CC Ort ONE 
