DECEMBER 31, 1896] 
NATURE 
215 
interfaces mercury-acid and acid-mercury, and it is upon these 
that the stress acts. The resistance is distributed along the 
tube, and is partly electrical, but toa far larger extent mechanical. 
It does not seem reasonable, therefore, to assume that the sole 
cause of delay is the ‘© polarisationsgeschwindigkeit ” of the 
meniscus. 
The author believes that in the case of an interface between 
two liquids, the rate of polarisation is to be measured in terms 
of the vibration period of a molecule, rather than in decimals of 
a second. 
Actual electrolysis does not take place in a properly working 
electrometer, except with electromotive forces greater than ought 
to be employed. 
According to the author, the capillary electrometer acts by 
transforming electrical into mechanical energy without any 
chemical interchange, this being possible because at the interface 
between two liquids which do not diffuse into each other the 
stress is so evenly distributed that no one molecule can be 
strained to a degree sufficient to detach any part of it until the 
stress is intense enough to break down all similar molecules 
simultaneously. 
In order to investigate the motion of the meniscus under the 
action of a varying electromotive force, such as a pulsating or 
alternating current, Hermann puts his equation into the form 
= + 7p — re f(t) = 
which is identical with the author’s formula for the estimation of 
the E.M.F., viz.— 
N+é%ar= 1 x fd) volt, 
0°0133 
Z.— 
- A constant The 
pine subs | BS multiple of the | = I A constant | E.M.F. | 
aca | distance from [{ — } multiple of at time ¢ 
22 URIS SEINE | the zero line in volts. 
From this formula it is evident at once that the E.M.F. is 
zero whenever N = — £Ar, and that the crossing of the zero line 
by the mensicus must always lag behind the change of sign of 
the E.M.F. Hence the curve can never come back to the zero 
line under the action of a current which pulsates but does not 
alternate. When N, ze. = vanishes, as it does at the apex of a 
spike or the bottom of a notch, the instantaneous value of the 
impressed E.M.F. is directly proportional to the distance of the 
meniscus from zero. The author has proposed that this method 
should be used to determine the characteristic current curves of 
dynamos.! 
Royal Meteorological Society, December 16.—Mr. E. 
Mawley, President, in the chair.—An interesting paper, by Dr. 
Leigh Canney, on the winter climate of Egypt, was read by the 
Secretary. The climate of Egypt during the winter is influ- 
enced by the Libyan desert, by the Mediterranean Sea, and by 
the extent of cultivated land. The author gave the results of 
a series of observations which he had carried on during the 
past three winters, The observations were started with the 
object of arriving at a comparative knowledge respecting the 
climates of the various stations now considered as health re- 
sorts in Egypt, and by a strictly comparable method to arrive 
at the precise differences between the climates of Upper and 
Lower Egypt, all previous observations having failed ‘in this 
respect. The stations at which observations were made were 
Cairo, Helouan, Mena House Hotel, Luxor, Assouan, Valley 
of the Tombs of the Kings, and the crest of the Libyan Hills. 
As self-recording thermometers and hair hygrometers were used 
at each station, valuable data have been obtained on the diurnal 
variation of temperature and humidity.—Mr. R. H. Curtis also 
read a paper on an attempt to determine the velocity equivalents 
of wind forces estimated’ by Beaufort’s scale. The author has 
compared the anémomietric records at Scilly, Fleetwood, Yar- 
mouth, and Holyhead, with the wind forces as estimated by 
the observers at the same or adjoining stations, and has by this 
method obtained a satisfactory table of velocity equivalents in 
miles per hour for the estimated forces by Beaufort’s scale. 
1 “The Capillary Electrometer in Theory and Practice.” 
from the Electrician of July 17 et seq., 1896.) 
NO. 1418, VOL. 55] 
(Reprinted 
Geological Society, December 16.—Dr. Henry Hicks,. 
F.R.S., President, in the chair.—On the subdivisions of the 
carboniferous series in Great Britain, and the true position of 
the beds mapped as the Yoredale series, by Dr, Wheelton Hind. 
In this paper the author gave a summary of the knowledge of 
the local division of the Carboniferous system, and criticised 
the present classifications in vogue, laying special stress upon 
the local variations in the lithological characters of the rocks, 
and summing up toa large extent the fossil evidence which is 
available. He maintained that the Yoredale beds were largely 
the equivalents of the beds which had elsewhere been referred to 
the Mountain Limestone series, though some local beds which 
had been included in the Yoredale series might rather be the 
equivalents of the millstone grit. He would divide the rocks 
of the Carboniferous system into an Upper Carboniferous or 
Anthraciferous series, and a Lower Carboniferous or Calcareous 
series ; and indicated the occurrence of three very different 
faunas in the Carboniferous rocks, viz.: (1) a Coal-Measure 
fauna rich in fish remains ; (2) the Lower Coal-Measure and! 
Grit fauna, largely marine but littoral ; and (3) a Limestone 
fauna, essentially marine, very rich in brachiopods.—Note on 
volcanic bombs in the Schalsteins of Nassau, by Prof. E. 
Kayser. The bombs forming the subject of this communica- 
tion occurred in two localities in the neighbourhood of 
Oberscheld near Dillenburg. They were generally rounded, 
though sometimes angular, and varied in size from that of a 
nut to that of a man’s head. Each consisted of a kernel of 
coarse-grained rock representing a fragment of limestone altered 
by metamorphism, surrounded by a rind of amygdaloidal rock 
due to the inclusion of the fragment in molten lava, They 
demonstrated the pyroclastic origin of. the Schalsteins, and also 
proved the similarity between the old Devonian volcanoes andi 
those which were now active. 
MANCHESTER. 
Literary and Philosophical Society, December 15.— | 
Prof. H. B. Dixon, F.R.S., in the chair.—Mr. J. C. Melvill 
read a paper on a collection of marine mollusca, mostly dredged 
by Mr. F. W. Townsend, who is officially connected with the 
Indian Oceanic Telegraph Company, whose cable extends from 
Kurachi to Bushire in the Persian Gulf. Mr. Townsend has 
made good use of the exceptional facilities he possesses for thus 
dredging the marine fauna, some forms being obtained attached 
to the cable itself, and some dredged in shallow, others in deep, 
water. The collections are of first-rate importance to the mala- 
cologist, the more so as this part of the North Indian Ocean has 
been curiously neglected in the past; the results have not yet 
been fully examined, but no less than thirty-two forms were 
described and differentiated as new to science. Of these the 
principal belonged to the genera Wassa, Sistrum, Terebra (one 
extraordinary form), J/z/va (also very unusual in appearance),. 
Turritella, Coralliophila, many Trocht, Dentalium, and, 
amongst Pelecypoda, Yo/dza (a particularly interesting tropical! 
form of an Arctic genus), Pectznculus, Tellina, Donax, Chrone,. 
and others. —On the ampullz on specimens of J/7//epora in the 
Manchester Museum, by Prof. S. J. Hickson, F.R.S. The: 
author stated that he had discovered ampulla on several speci- 
mens in the museum, At least one of these belongs to the West 
Indian species WZ. adcécornzs, and the observation suggests that 
all species of AZz//epora at some time produce medusz similar to 
those of the Pacific Ocean species JZ. murray. 
PARIS. 
Academy of Sciences, December 21.—Annual Meeting.— 
M. A. Cornu in the chair.—The President’s address was chiefly 
occupied with an historical retrospect of the X-rays. The losses 
by death during the year include the names of Fizeau, Tisserand, 
Reiset, Sappey, Daubrée, Resal, and Trécul.—The Arago medal 
has been awarded twice during the year, to M. A. Abbadie and 
to Lord Kelvin. The prizes offered for the present year have 
been awarded as follows :—In the section of Mathematics, the 
grand prize to M. E. Maillet for his work on the theory of sub- 
stitutions, the Bordin prize to M. Jacques Hadamard for his 
memoir on the theory of geodesic lines, the Francoeur prize to 
M. A. Valson, and the Poncelet prize to M. Painlevé for general 
contributions to mathematics. In the section of Mechanics,. 
the extraordinary prize of 6000 fr. is divided between MM. 
Darrieus (for a work on the improvement of the naval forces), 
