Marcu 11, 1897 | 
NATURE 
455 
manometer. The manometer has a tube with a rise of 4 or 5 
in 100, and is provided with a pivotal mounting and a level. 
The pressure near the train is comparatively small, and increases 
as the collector is thrust further out. It approaches a limit cor- 
responding to the train velocity at the instant. Prof. Nipher 
finds the relation between the limiting pressure and velocity to 
agree exactly with the formula 
where @ is the train velocity in centimetres per second, P is the 
pressure in dynes to the square centimetre, and 6 is the density 
of air in C.G. units at the temperature and pressure of the 
observations. He finds the pressure a maximum when the axis of 
the collector is parallel to the direction of motion with the mouth 
to the wind. Turning the collector until its axis makes an angle 
of about 60° with this position, the pressure reduces to zero. 
At greater angles the pressure becomes less than atmospheric 
pressure by an amount which reaches a maximum at an angle of 
go’, and passes through a minimum at an angle of 180°, when 
the collector is in a trailing position. The sum of the coeffi- 
cients for the two positions of maximum compression and 
minimum exhaust is almost exactly the same as Langley 
obtained with a pressure board when exposed normally to the 
wind. The result shows that a large amount of air is dragged 
along with the train, the motion being communicated to air 
many feet away. This air is a source of danger to one standing 
too near the train when at full speed. One is likely to be 
toppled over, and the blow of the air communicates a motion of 
rotation which may cause one to roll under the train if the 
nature of the ground does not prevent such a result. It was re- 
marked, however, that where trains have a right to run at any 
speed, no prudent person would stand so near to a train as is 
necessary in order to be in danger from this source.—The fol- 
lowing officers were declared elected for the year 1897 :—Presi- 
dent: M. L. Gray. First Vice-President: E. A. Engler. 
Second Vice-President: Charles R. Sanger. Recording Secre- 
tary: William Trelease. Corresponding Secretary, E. C. 
Runge. Treasurer: Enno Sander. Librarian: G. Hambach. 
Curators: Julius Hurter, J. H. Kinealy, E. Evers. Directors : 
M. H. Post, Joseph Grindon. (Signed) William Trelease, 
Recording Secretary. 
AMSTERDAM. 
Royal Academy of Sciences, January 2.—Prof. Stokvis 
in the chair. —Mr. Jan de Vries on accelerations of plane motion. 
—Mr. Jan de Vries read a second paper on geometrical proofs of 
arithmetical theorems. —On behalf of Mr. Gegenbauer, of 
Vienna, on the resultant of two consecutive denominators of a 
certain regular continuous fraction.—Prof. J. A. C. Oudemans 
made a communication concerning the contents of the fifth 
section of his report on the triangulation of Java. Of all the 
sides, both the primary and the secondary ones, it contains the 
azimuths and the distances. According to the author’s calcula- 
tions, the latter ought to be increased by about two-millionths, 
to be reduced to métres des Archives, but by about four- 
millionth, to reduce them to metres Internationaux. It is true 
that the ‘* Comité International,” trusting to measurements 
executed by the *‘ Commission mixte,” assumes the above-men- 
tioned standards to be equal in length (though this equality has 
not been controlled by direct comparison), but the measurements 
carried out by the Netherlands Committee for the métre led to 
the result that the métre International is shorter than the métre 
des Archives by more than 2 4. At the close of the work the 
wish is uttered ‘‘that the Comité mixte may as yet decide to 
execute a series of direct comparisons at oC. and at high 
temperatures, between the métre International and the métre des 
Archives. —Prof. Lorentz, on behalfof (a) Mr. A. Smits : Measure- 
ments with the micromanometer. This instrument, with which 
differences of pressure as small as 1/4000 mm. of mercury can 
be observed, consists of a U-shaped tube, the upper parts of 
whose legs are widened. It contains two fluids, viz. aniline 
in the lower and narrower part, and upon it, on either side, a 
quantity of water, whose surface is in the wider part of the tube ; 
the position of the plane separating the two fluids is read with a 
kathetometer. The object of the research (conducted in the 
Utrecht Physical Laboratory) was to determine the difference 
between the vapour pressure at o C. of pure water and that of 
very dilute solutions, For this purpose it was necessary to 
NO. 1428, VOL. 55] 
exhaust the manometer with a mercurial air-pump, some oil 
being poured on the water on both sides, and to arrange suitable 
connections either between the two legs or between them and 
bulbs containing water anda solution. For all these connec- 
tions mercury joints were employed. Bulbs containing PO; 
and H,SO, served for drying, the latter substance at the same 
time for the absorption of aniline vapour. The measurements 
were made with solutions of NaCl, KOH, and cane-sugar, the 
number of gramme molecules in 1000 gr. of water varying in the 
first case from 1°83 to 0'020, in the second case from 2°64 to 
0013, and in the last case from 1°88 to 0021. The coefficient 
Zin Van 't Hoff’s well-known formula was found to be constant, 
by 1 for the sugar solutions, but the two other substances 
yielded values diminishing with decreasing concentration. The 
extreme numbers were 1°77 and 1°40 for NaCl and 2'17 and 
1°5 for KOH. (4) Prof. V. A. Julius (Utrecht) on the question : 
Is the maximum vapour pressure solely a function of tempera- 
ture? After having discovered the causes of the irregularities 
presented by the micromanometer in the first stage of Mr. Smit’s 
experiments (a trace of aniline vapour sufficed to prevent the 
regular condensation of the vapour of water), the author could 
put to a very severe test the opinion expressed by Willner and 
Grotrian (Wed. Ann., vol. xi. p. 545), according to which a 
vapour can be compressed above what is commonly called its 
maximum tension, even though a certain quantity of the liquid 
be present. Experiments with water and a solution of NaCl 
at o° C. did not confirm this view. A space containing a suff- 
cient amount of the liquid and filled for the remainder with 
saturated vapour, could be diminished by + of its original volume. 
In this way a temporary elevation of pressure was produced, but 
in a short time the original pressure was re-established by con- 
densation. A change of pressure as small as 1/18000 of its 
value could have been detected.—Prof. Van der Waals presented 
for publication in the Academy's Proceedings ; (1) On behalf of 
Prof. Kamerlingh Onnes a paper, by Mr. L. H. Siertsema, on 
an investigation carried out in the Leyden Physical Laboratory, 
concerning the influence of pressure upon the natural rotation of 
the plane of polarisation in solutions of cane-sugar. (2) On 
behalf of Prof. C. A. Lobry de Bruyn and Mr. W. Alberda van 
Ekenstein, a communication to the effect that the chitosamine 
from chitin (hitherto wrongly called glucosamine) can be 
obtained in the free and the crystallised state from the hydro- 
chloric salt and methylalcoholic sodium. It easily changes into 
another crystalline body, which can be prepared direct from 
fructose (levulose) and methylalcoholicammonia. Consequently 
there isa relation between the last-mentioned sugar and that 
from which chitosamine is obtained. With silver carbonate 
HCI chitosamine yields through oxidation a substance, which 
with phenyl-hydrazine directly gives abundant glucosazon at 
about 70°, and so it may be glucoson (which isa keton-aldehyde). 
(3) On behalf of Mr. D. F. Tollenaar, a paper on some experl- 
ments with two kathodes, square aluminium plates, the distance 
of which could be varied. The phosphorescence figures on the 
wall of the globular screen consisted of a zone of very intense 
green, bordered on either side by two rings. By changing the 
intensity of the current towards one of the kathodes, the motion 
of one of the rings was found to obey the rules of deflexion 
figures given by Goldstein, but the other ring behaved quite 
differently. Whena triangular or square plate was used, and a 
metal globe as screen, remarkable shadows were obtained, viz. 
a triangle and a square respectively, which looked as if turned 
through angles of 60° and 45° with respect to the kathode (4) 
On behalf of Mr. S. Kriiger, S.J., a paper on the ellipsoidal 
forms of equilibrium of a_ revolving homogeneous liquid 
body. Prof. G. H. Darwin (Proc. Roy. Soc., xii.) does 
not sufficiently account for the method of disregarding 
errors, which he proposed in the case of very elongate 
ellipsoids. The kinetic energy of the revolving motion in 
the case of Jacobi’s ellipsoid does not become a maximum 
‘when the length of the ellipsoid is about five times its 
diameter” (¢.c., p. 334), but when the ratio of the longest to the 
shortest axisis about 93. When the halves of the axes of Jacobi’s 
ellipsoid are represented by a, 4, and c, and this series of forms 
of equilibrium is continuous, so that a® — }*/a” — > increases from 
o to 1, then an infinitely great number of bifurcation forms 
(Poincaré, Acta mathent., vil.) are met with, but 7zof amy one of 
these figures ts found as long as a — ba? — cL}. The limit 
torm of the ellipsoids of revolution.is at the same time a 
bifurcation form, with a series of non-ellipsoidal forms of 
equilibrium. 
