554 
suitable balance among the various optical corrections 
differs somewhat from the one generally accepted 
for the other branches of microscopy ; in particular, 
flare should be reduced to the absolute minimum. 
The requirements of metallurgical microscopy are 
sufficiently distinct to justify the production of 
objectives computed and designed specially for this 
work, 

Paris. 
Academy of Sciences, March 26.—M. G, Bigourdan 
in the chair—R. de Forcrand: Thallium hydroxide, 
The usual method of preparing thallium hydroxide 
by precipitation of the sulphate with baryta is very 
tedious, and liable to give an impure product. A 
better method is to treat thallium ethylate, C,H; . OTI, 
with water and starting with TIOH and T1,O prepared 
in this way, the thermochemical constants have been 
redetermined.—M. Soula: Taylor’s series having an 
infinity of zero coefficients.—P. Noaillon : A harmonic 
function the gradient of which vanishes at infinity.— 
Henri Chrétien: Recording time, in figures, to the 
thousandth of a second, with an electrically main- 
tained pendulum. A description, with illustrations, 
of a new recording chronograph of simple construc- 
tion.—G. E. Beggs: The exact solution of problems 
indeterminate statically by means of paper models.— 
M. Lafay: The possible use of the microphone to 
facilitate problems of flight.—J. Trousset: Can the 
observation of the planets furnish arguments for or 
against relativity? The author gives reasons for 
answering this question in the negative.—Paul 
Mondain-Monval: The variation of heats of solution 
with temperature. Details of experiments on heats 
of solution of potassium, sodium, and ammonium 
nitrates, potassium sulphate, and ammonium and 
potassium chlorides at 0° and 18° C.—Th. Tommasina : 
Contribution to the dynamo-kinetic theory of the 
electron and the atom.—Georges Déjardin: The 
critical velocities of the electrons in krypton and 
the production of the spectra of this gas. An 
account of work done with a three electrode tube 
of an improved type. The ionisation potentials of 
argon and krypton were found to be 15:2+0:2 volts 
and 12:7+0-2 volts respectively : the double ionisa- 
tion potentials were 34:0 volts and 28-25 volts. 
Krypton, like argon, gives two spectra, details of 
which are given.—Albert Portevin: The variations 
of capacity accompanying the thermal treatment of 
hollow steel bodies. Study of the influence of the 
tempering temperature, rate of cooling, and hardness 
of steel on the changes of capacity of steel shells.— 
L. J. Simon and M. Fréjacques: The methylating 
and sulphonating action of methyl sulphate on 
phenols in the absence of water. This reaction is 
very complicated. With phenol at least eight sub- 
stances are present: methyl ether, anisol, phenol 
and anisol sulphonic acids and their methyl esters, 
and methylsulphuric acid. The methods of separa- 
tion are given.—A. Mailhe: A new preparation of 
the tetrasubstituted ureas. The formamide of methyl- 
aniline, C,H, . N(CH;)(COH), passed as vapour over 
finely divided nickel at 380°-400° C. gives sym- 
metrical dimethyl-diphenylurea, CO(N(CH3)(C,Hs))2. 
That the method is of general application is proved 
by other examples.—F. Bordas and T. Touplain: 
The denaturation of ethyl alcohol. The use of 
alcohol as a constituent of a motor fuel requires a 
cheaper denaturant, and one easily detected. The 
use of methyl or ethyl borate is suggested.—P. 
Gaubert: The liquid crystals of anisal-p-amido- 
azotoluene. A reply to some criticisms of G. Friedel. 
—M. Solignac: The tectonic of the plain of Mateur 
and its approaches (Tunis).—F. Baldet : Contribution 
NO. 2790, VOL. 111] 
NATURE 
[ApriL 21, 1923, 
to the study of atmospherics. A method of searching 
for and partially eliminating low frequency parasitic 
currents of atmospheric or telluric origin.—Pierre 
Dangeard: The vacuome in the pollen grains of 
Gymnosperms. Application of the vital coloration 
method (neutral red) to the study of the pollen’ 
grains of Taxus baccata, Cephalotaxus Fortunei,. 
Cupressus Lawsonia, and Pinus Armandi.—Mlle. . 
France Gueylard: Intervention of the spleen in the 
phenomena of adaptation to changes in salinity. 
It is known that Gasterosteus aculeatus can be trans-. 
ferred from fresh to salt water, and rapidly adapts 
itself to the change of medium. It is shown i= 
change in the salinity of the medium results in. 
changes in the spleen, the higher the proportion of 
salt in the water, the greater the reduction in the 
proportional weight of the spleen.—Marcel Duval- 
and P. Portier: The impermeability to urea of certain 
tissues of selacian fishes——Jules Amar: The law of 
vivireaction in biology and pathology. This law is 
stated thus: any pathological or physico-chemical 
act which tends to reduce the phenomena of organic. 
oxidation provokes, by a defence mechanism, a 
relative increase of the pulmonary ventilation.— 
L. M. Betances: The specific differentiation of the 
hematic cell in the Metazoa.—André Lwoff: The 
nutrition of the Infusoria. Although, under natural 
conditions, the nutrition of free infusoria is purely 
phagocytic, it is possible, in a suitable medium, to 
feed some species by means of dissolved substances. 
—Boris Ephrussi and André Lwoff: The double. 
cyclic periodicity of the zone of division in Colpidium 
colpoda. 
WASHINGTON. 
National Academy of Sciences (Proc. Vol. 9, No. I, 
January).—H. W. Brinkmann: On Riemann spaces: 
conformal to Euclidean space. An n-dimensional 
Riemann space can be ‘‘ imbedded ”’ in an (+2)- 
dimensional Euclidean space.—O, Veblen: Equiaffine 
geometry of paths. A definition of volume which 
generalises that used in Riemann geometry is derived. 
—L. P. Eisenhart: Affine geometries of paths 
possessing an invariant integral—J. R. Kline: 
Closed connected sets which are disconnected by the 
removal of a finite number of points.—R. S. Wood- 
ward: Some extensions in the mathematics of 
hydromechanics. A development of some of the 
equations used to describe fluid motion when 
viscosity is taken into account.—P. D. McMaster 
and P. Rous: Hydrohepatosis, a condition analogous * 
to hydronephrosis. Prolonged obstruction of the 
bile duct in dogs causes distention of the duct and 
of the gall-bladder with ‘‘ white-bile,” a colourless, 
watery fluid. A pressure obstacle causes reduction” 
in total secretion and in the percentage output of 
some of the substances secreted, as in kidney obstruc- 
tion, though the distention caused is less marked.— 
H. Laugier and R. Legendre: Novocaine and curarisa- 
tion. Novocaine causes morphological changes in 
nerve fibre, and a solution (1 in 10,000) in physiological 
salt solution causes an increase in the intensity of 
a suddenly established current necessary to provoke 
visible muscular contraction, and decreases the 
interval before response occurs.—F. G. Benedict and 
E. G. Ritzman: Under-nutrition and its influence on 
the metabolic plane of steers. Eleven adult steers 
were fed for about 44 months on one-half their 
original maintenance ration. Changes in body 
tissue were measured by the carbon dioxide output, 
using a respiration chamber. At first there was 
rapid reduction in live-weight, due to changes im 
intestinal ballast or fill; afterwards there was slow 
steady loss, due to drafts on body material; and 
