762 
NATURE 
[June 2, 1923, 

in proportion to the change in the number ot particles 
which aggregate—A. L. Norbury: Some experi- 
ments in the hardness and spontaneous annealing 
of lead. When Brinell hardness tests are made in 
lead the “ time factor’’ is an important variable. 
The load, therefore, has to be applied and removed 
almost instantaneously and loads up to 300 kg. 
only can be used with a 10 mm. ball. Loads were 
maintained for varying lengths of time and the 
results are interpreted according to Meyer’s formula 
L =ad", where L is the load, d the diameter of the 
impression, and a and 7 constants. It appears that 
the more annealed the lead the more the results 
are affected by the time factor. With cold-hammer- 
ing, lead is spontaneously annealed at room tempera- 
ture, and the rate of annealing increases with the 
amount of deformation, so that lead which has been 
severely hammered shows no increase in hardness.— 
D. Stockdale: An example of polymorphism in an 
intermetallic compound. A study of the liquidus 
of the copper rich aluminium-copper alloys shows 
that the compound Cu,Al exists, but is unstable 
above ro15° C. The compound can probably exist 
in two polymorphic forms.—F. C. Thompson and 
E. Whitehead : Some notes on the etching properties 
of the a- and §8-forms of carbide of iron. The 
transformation of iron carbide at 200° C. has been 
studied from the point of view of the etching properties. 
The effects, positive or negative, of numerous reagents 
are recorded. The best reagent for differentiating 
between the two forms of carbide was found to be 
potassium copper cyanide. Incidentally the self- 
tempering of samples of white iron quenched from 
below 300° C. was confirmed. 
CAMBRIDGE. 
Philosophical Society, May 7.—Mr. C. T. Heycock, 
president, in the chair.—G. D. Liveing : The recupera- 
tion of energy in the universe.—J. E. Purvis: (1) 
Infra-red spectra. (2) The absorption spectra of 
some organic and inorganic salts of didymium. 
(3) The absorption spectra of solutions of benzene 
and some of its derivates at various temperatures. 
(4) The absorption of the ultra-violet rays by phos- 
phorus and some of its compounds.—E. C. Stoner: 
A note on the electromagnetic mass of the electron. 
—R.-R. S. Cox: Chemical constants of diatomic 
molecules. 
May 21.—P. A. MacMahon: (1) The partitions of 
infinity. (2) The prime numbers of measurement. 
—M. H. A. Newman: On approximate continuity.— 
J. P. Gabbatt: The pedal locus in hyperspace.— 
D. R. Hartree: On some approximate numerical 
applications of Bohr’s theory of spectra,—A. G. 
Thacker: Some statistical aspects of geferephical 
distribution.—J. Walton: On the structure of a 
middle Cambrian Alga from British Columbia (Mar- 
polia spissa, Walcott).—F. T. Brooks and W. C. 
Moore: On the invasion of woody tissues by wound 
parasites. 
DUBLIN. 
Royal Irish Academy, April 23.—Prof. Sydney 
Young, president, in the chair—W. McF. Orr: 
Solutions of systems of ordinary linear differential 
equations by contour integrals. The writer starts 
with the equation ¢(D)v=f(t), where ¢ is a poly- 
nomial of degree vy. The solution, subject to the 
conditions that iritially ¥ and its derivatives up to 
(r—1)** shall have given values, may be written 
[ent 
= 5 “ 
arin = i 50) (= 2 #0) ja+ | ail, eXt-t F(t’) at’, 
where the integrals with respect to » are taken 
round a contour which encloses all zeros of ¢()). 
NO. 2796, VOL. 111] 

Not only is this solution verified, but it is also 
obtained from the original equation. This is done 
by changing the independent variable to ¢’, multiply- 
ing across by eAt—)dt’, integrating from o to 4, 
multiplying across by d\/#(\), and integrating round 
an infinite contour. Simultameous equations are 
solved similarly. 
Paris. 
Academy of Sciences, May 7.—M. Albin Haller 
in the chair.—The president announced the death 
of Sir James Dewar, corresponding member of the 
general physics section—Henri Lebesgue: The 
singularities of harmonic functions—M. Mesnager : 
Observations on a communication by M. Sudria 
(April 23)—L. Joubin: The cruises proposed by the 
Office scientifique et technique des péches during 
1923. A programme of the work proposed for the 
coming season on the Pourquoi Pas? under M. 
Charcot and on La Tanche, under M. Rallier du 
Baty.—M. d’Ocagne: Equations with four variables 
representable both by simple and double alignment. 
—C. Depéret and L. Mayet: The phyletic branches 
of the elephants.—M. Marin Molliard was elected 
a member of the section of botany, in succession to 
the late M. Gaston Bonnier.—Pierre Humbert: 
Certain orthogonal polynomials. —Paul Lévy: The 
stable laws in the calculus of probabilities —Bertrand 
Gambier: Systems of superabundant points in the 
plane: application to the study of certain surfaces. 
—Jean Dufay: The spectrum of the nocturnal sky. 
In the part of the spectrum studied (plate excludes 
the green and yellow) the light of the sky at night 
has qualitatively the same composition as sunlight. 
E. Fichot: The peculiarities of .the amphidromic 
regime of open seas.—S. Rabinovitch: The geo- 
metrisation of electromagnetic forces.—Pierre Auger 
and A. Dauvillier: The existence of new lines, one 
a Sommerfeld doublet, excluded by the principle 
of selection, in the L series of the heavy elements.— 
Victor Henri: The ultra-violet absorption spectrum 
of the vapour of benzene chloride. A reproduction 
of the spectrum is given, together with a diagram 
showing its decomposition into groups and series. 
From the spectrum the molecule would appear to 
be asymmetrical.—Mlle. I. Curie and G, Fournier : 
The y radiation of radium-D and radium-E. The 
results are in good agreement with those found by 
Rutherford and Richardson. In addition the exist- 
ence of a penetrating radiation due to radium-E 
has been established and its coefficient of absorption 
determined. —Suzanne Veil: The evolution of the 
molecule of chromium hydroxide in water.— H. 
Pélabon: The thermoelectric power of alloys. For 
alloys not forming definite compounds the thermo- 
electric power usually lies between the values 
corresponding to those of the pure metals, but the 
thermoelectric power can never be calculated by 
the mixture rule. Results for lead-antimony alloys 
are given.—M. Aubert and G. Dixmier: The stability 
of alcohol-petrol mixtures in the presence of water. 
The results are summarised in two diagrams showing 
the effects of the gradual addition of water to alcohol- 
petrol mixtures, with special reference to the point 
at which separation into two layers takes place.— 
M. Sauvageot and H. Delmas: The possibility of 
tempering extra mild steel at a very high temperature. 
As the amount of carbon in steel diminishes, approach- 
ing pure iron, the critical tempering temperature 
rises rapidly, and coincides with the melting - point 
when the carbon is a little less than 0-09 per cent. 
(with manganese 0:33 per cent.).—Paul Mondain 
Monval: Eutectic points in saline solutions.—Robert 
Stumper: The corrosion of iron in the presence of 
iron sulphide. Experiments showing that iron in 
