22 
DUBLIN 
University Experimental Science Assoziation, March 
16.—The following commanications were made :—Prof. J. E. 
Reynolds, on action of silicon tetrabromide on thiocarbamide. 
—Mr. H. L. Crosthwait, the Forth Bridge.—Oa the melting- 
points of minerals, by J. Joly, B.E. An account of experi- 
ments with the meldometer, in which the temperature of the 
platinum strip, acting as the stage of a microscope, was deter- 
mined in terms of its resistance according to Siemens’s formula. 
It was mentioned that the order of fusibility assumed in Van 
Kobel’s scale is erroneous. The true order seems to be: (1) 
stibnite ; (2) natrolite ; (3) adularia ; (4) actinolite ; (5) bronzite ; 
(6) almandine. The blowpipe being a powerful chemical agent, 
may evidently mask the phenomena of fusion with secondary 
effects. Fair comparison is impossible with it, the shape and 
conductivity of the specimen used affecting the result. Com- 
parison on the meldometer is not open to these objections. It 
is very advisable that a scientific scale of fusibility should be 
adopted for the use of mineralogists. If this scale rested on the 
melting points of easily-prepared salts, it would then always be 
easy to determine by comparison the melting-point of a mineral. 
Approximate determinations could thus be readily effected on 
very minute quantities of matter. In the author's experiments 
the substances are reduced to a fine powder, the phenomena 
attending fusion being observed with a 1” object-glass. These 
phenomena are often very characteristic and beautiful. 
PARIS 
Academy of Sciences, April 27.—M. E. Blanchard in 
the chair.—On the quantitative analysis of the organic carbon 
contained in soils which absorb free nitrogen, by M. Berthelot. 
The author’s researches on the direct absorption of free nitrogen 
by various argillac-ous soils through certain minute organisms 
have led him to seek some other measure capable of indicating 
the proportion of these organisms in the ground. It being 
apparently impossible to isolate them, some idea of their abund- 
ance may still be formed by a quantitative analysis of the carbon 
entering into the constitution of their tissues. Hence the present 
inquiry, which promises to raise sone new and extremely 
delicate problems.—Observations relative to the proportion and 
quantitative analysis of the ammonia present in the ground, by 
MM. Berthelot and André. The experinents conducted during 
the last four years by the authors at Meudon on the general 
growth of vegetation and on the formation of nitric compounds, 
both in plants and in the soil, have led to certain observations 
here communicated on the processes employed in the quantitative 
analysis of the ammonia and the starchy compounds. It is 
inferred generally that the analysis of the ammonia present in 
the soil should be made without any desiccation, and that arable 
ground, when watered, tends continually to liberate the ammonia 
of the ammoniacal salts contained in it.—On the nitric sub- 
stances contained in rain-water, by MM. Berthelot and André. 
A process is explained for determining by analysis the exact 
quantity of nitric substances conveyed to the earth by meteoric 
waters.—On the movements of meteorites in the atmosphere, by 
M. Faye. These remarks are made in connection with 
M. Daubrée’s essay on ‘‘ Meteorites and the Constitution 
of the Terrestrial Globe,” recently presented to the Academy 
by the author.—Discourse pronounced at Montdidier on the 
occasion of the celebration of the Parmentier centenary, by 
M. Chatin.—Note on the meteorological observations made 
at the Montpellier School of Agriculture since last summer 
with the registering actinometer, by M. A. Crova. The 
results already obtained for the variations of solar radiation 
in summer require to be modified for the autumn and winter 
seasons. In autumn the oscillations diminish in amplitude, the 
two maxima of heat intensity tending continually to approach 
each other and gradually merge together about noon in winter. 
—Note on M. Leewy’s formulas for the reduction of the circum- 
polar stars, by M. Gruey. A process, at once simple and easily 
remembered, is given for establishing all M. Leewy’s formulas 
without any sacrifice of accuracy.—Remarks on the appearance 
of Fabry’s comet in April 1886, by M. G. Rayet. The comet, 
observed at Bordeaux on April 7, 13, and 21, exhibited a very 
long continuous spectrum from the extreme red to the violet, 
corresponding with the light of the nucleus and of the three 
ordinary bands of cometary spectra.—Note on the equilibrium 
of a fluid mass in rotation, by M. H. Poincaré. Some explana- 
tions are offered in connection with M. Matthiessen’s note in- 
NATURE 
[May 6, 1886 
serted in the Comptes rendus for April 12.—On the magnetic rota- 
tory power of the crystalline bodies, by M. Chauvin. Iceland spar 
and some other birefractive crystals, supposed by Faraday and 
others to be inactive, are shown to possess the property of mag- 
netic rotation.—Action of alcoholic potassa on urea, sulpho-urea, 
and some substituted ureas; inverse reaction of the artificial 
urea prepared by Wohler’s process, by M. Alb. Haller. —Note 
on two properties of the urethanes of the fatty series, by M. G. 
Arth.--On the abnormal secretion of nitric substances in yeast 
and mould, by MM. U. Gayon and E, Dubourg.—Remarks on 
Polystigma fulvum, Tulasne, a new disease of the almond-tree, 
by M. Maxime Cornu.—Propagation of the luminous sensation 
to the non-excited zones of the retina, by M. Aug. Charpentier. 
From his optical experiments the author concludes that, in the 
phenomenon of successive luminous induction, the nervous 
action which gives rise to the sensation is really transmitted to 
the parts of the percipient medium lying near the excited part. 
—An attempt at a physiological explanation of the phenomenon 
of complementary colours, by the late M. Tréve.—Heliophoto- 
graphy and the magnetic perturbation of March 30, 1886, by 
M. Ch. V. Zenger.—Observation of an aurora borealis at 
Rolleville, Seine Inférieure, coincident with the magnetic pertur- 
bation of March 30, by the Abbé Maze. 
BERLIN 
Physical Society, February 19.—Dr. Pernet reported on 
the part he had taken in the labours of the International Com- 
mission which had for their object the comparative determina- 
tion of the normal metre. After recounting in a brief historical 
survey the undertakings carried out in Paris at the end of last 
century by an International Congress, which, after theoretically 
determining on the kilogramme and the metre as normal units, 
produced a normal metre and normal kilogramme of platinum, the 
speaker discussed the events which in 1878 led to a new interna- 
tional agreement, in consequence of which a new normal metre 
of platinum-iridium of X-form was prepared and compared with 
the metre of the Archives. A series of national standards was 
also compared with the normal metre. The speaker described 
in a searching manner the arrangements of the Bureau in which 
the comparisons were undertaken, the contrivances for securing 
the several comparing rooms against outward disturbances, the 
means adopted for insuring constant temperatures, and the 
methods employed in the comparisons, as also in the determina- 
tion of the expansion coefficients of the rods used. Finally he 
gave a sketch of his own labours, which had for their object the 
comparison of a series of normal metre rods of different metals 
with the metre of the Archives, and the determination whether 
repeated heatings and coolings between 50° and o° C., whether 
concussions, and whether time caused any perceptible changes in 
the lengths of the rods. As the result of these investigations it 
was found that the compared national standards, together with 
their divisions, were exact up to one-thousandth of a millimetre ; 
that, with the exception of steel, which, on account of its changes 
in hardness, readily yielded modifications of volume and length 
in the rods made of this material, all the metals out of which 
the standards were made—namely, platinum-iridium, platinum, 
and brass—furnished material suitable for normal metre rods 5 
and that repeated heatings and concussions induced no changes 
passing beyond the limits within which observation fails. —Herr 
C. Baur described experiments he had made with water-jets, 
which, issuing from a conically-pointed tube in parabolic curves, 
were acted upon by certain musical tones so that at some distance 
from the mouth of the tube they showed a rotation, and that the 
jet, though broken up into drops behind the apex of the parabola, 
contracted into a continuous jet. The thinner was the jet the 
higher must be the tone towards which it was sensitive; the 
thicker the jet the deeper the tone. Herr Baur had instituted 
further experiments with water-jets, which he caused to fall on 
plates. Under certain circumstances there thus arose quite pure 
tones, which continued as long as the jet hit on the plate. The 
experiments succeeded best with a Weissmann apparatus, when 
the jet issued under a pressure of 10 cm. water from a lateral 
opening of 4 mm. in diameter without tube. Thin window-glass 
plates and metal plates, which, resting on pedestals, had free 
movement of vibration, were best suited as receiving-plates. 
The tone was most certain of occurrence when the node lines 
of the plates were supported. In the jet itself appeared nodes and 
ventral segments at some distance from the opening ; they were 
most distinct and regular at its middle ; away in the direction 
of the plates they again became indistinct. If the metal plate 
