Nov. 23, 1882] 
NATURE 
25 
Porcupine. This part, which embraced the species from the 
Solenoconchia to the Calyptracidz, comprised sixty-nine species, 
of which twenty two were now for the first time described or 
figured. The geographical, hydrographical, and geological 
range of all these species was given, as in his former papers ; 
and the author especially noti.ed the points of agreement 
between the deep-water Mollusca from the American and 
European expeditions. 
Physical Society, November 1i1.—Prof. Clifton, president, 
in the chair.—Prof. Rowland, of Baltimore, exhibited a number 
of his new concave gratings for giving a diffraction spectrum. 
He explained the theory of their action. Gratings can be rnled 
on any surface if the lines are at a proper distance apart and of 
the proper form. The best surface, however, is a cylindrical or 
spherical one. The gratings are solid slabs of polished speculum 
metal ruled with lines equidistant by a special machine of Prof. 
Rowland’s invention. An account of this machine will be published 
shortly. The number of lines perinch varied inthe specimens shown 
fro n 5000 to 42,000, but higher numbers can be engraved by the 
cutting diamond, One great advantage of their use is that the rela- 
tive wave-lengths can be measured by the micrometer with great 
accuracy. Theauthor has designed an ingenious mechanical arrange- 
ment for keeping the photographic plates in focus. In this way 
photographs of great distinctness can be obtained. Prof. Rowland 
exhibited some Io inches long, which showed the E-line doubled, 
and the large B groups very clearly. Lines are divided by this 
method which have never been divided before ; and the work of 
photographing takes a mere fraction of the time formerly re- 
quired. A photographic plate sensitive throughout its length is 
got by means of a mixture of eocene, iodised collodion, and 
bromised collodes. Prof. Rowland and Capt. Abney, R.E., 
are at present engaged in preparing a new map of the whole 
spectrum with a focus of 18 feet. In reply to Mr. Hilgar, F.R.A.S., 
he stated that if the metal is the true speculum metal used by 
Lord Rosse, it would stand the effects of climate he thought ; 
but if too much copper were put in it might not. In reply to 
Mr. Warren de la Rue he said that 42,coo was the largest 
number of lines he had yet required to engrave on the metal.— 
Prof. Guthrie read a letter from Capt. Abney, pointing out 
Prof. Rowland’s plates gave clearer spectra than any others ; 
they were free from ‘‘ghosts” caused by periodicity in the 
ruling ; and the speculum metal had no particular absorption.— 
Prof, Dewar, F.R.$., observed that Professor Liveing and he 
had been engaged for three years past in preparing a map of the 
ultra-violet spectrum, which would soon be puolished. He con 
sidered the concave gratings to make a new departure in the 
subject, and they would have greatly facilitated the,preparation of 
his map.—Mr. W. R. Browne then read a paper on the conser- 
vation of energy and central forces. He showed that the doctrine 
of the conservation of energy necessarily involved central forces 
and could not be proved unless on the assumption of a system of 
central forces. This involved the hypothesis of Boscovich that 
matter consists of a collection of centres of force, and the author 
criticised the objections of Clerk Maxwell, Tait, and others to 
Boscovich’s theory. The paper will appear in the 7vamsactions 
of the Society.—Prof. S. P. Thompson read some historical 
notes on physics, in which he showed that the voltaic arc between 
carbon points was produced by a Mr. Etienne Gaspar Robertson 
(whose name indicates a Scotch origin) at Paris in 1802. This 
-reference is found in the Yournal de Paris for that year. Lako- 
ratory note-books at the Royal Institution, however, are said to 
show that Davy experimented with the arc quite as early. The 
experiment usually attributed to Franklin of exhausting air from 
a vessel of water ‘‘off the boil” and causing it to boil afresh, is 
found in Boyle’s ‘‘ New Experiments touching the Spring of the 
air. Prof. Thompson also exhibited an early Reis’s telephone, 
made by Philip Reis in 1861 at Frankfort, and designed to 
transmit speech. It was modelled on the human ear, one form 
of transmitter being a rudely-carved wooden ear, with a tympan, 
haxing a platinum wire behind, hard pressed against a platinum- 
tipped adjustible spring. Prof. Thompson showed by various | 
proofs that words were actually sent by that and similar 
apparatus, 
Meteorological Society, November 15.—Mr. J. K. Laughton, 
F.R.A.S., president, in the chair.—Eleven new Fellows were 
elected, viz. Rev. J. Brunskill, F. B. Buckland, C. F. Casella, 
W. H.M. Christie, F.R.S., A. Cresswell, R. S. Culley, C. 
Morris, O. L. O’Connor, H. Parker, F.Z.S., A. Rowntree, and 
D. R. Sharpe.—The yapers read were: On certain types of | 
British weather, by the Hon. Ralph Abercromby, F.M.S. The 
author shows that there is a tendency of the weather all over the 
Temperate Zone to occur in spells associated with certain types 
of pressure distribution. In Great Britain there are at least four 
persistent types—the southerly, the westerly, the northerly, and 
the easterly. In spite of much fluctuation, one or other of these 
types will often continue for weeks together, and tend to recur 
at the same date every year. The value of the recognition of 
type groups is shown in the following ways :—(1) They explain 
many phenomena of weather and many popular prognostics ; 
(2) in some cases they enable forecasts to be issued with greater 
certainty and fora longer time ahead ; (3) we can by their means 
correct Statistical results by giving the real test of identity of 
recurrent weather which no single item such as heat, cold, rain, 
&c., can do; (4) they enable us to treat such geological questions 
as the influence of changing distribution of land and sea on cli- 
mate in a more satisfactory manner than any other method.—On 
the use of kites for meteorological observation, by Prof. E. 
Douglas Archibald, M.A., F.R.S. In this paper the author 
advocates the use of kites for meteorological observation, and 
describes the mode in which they may be best flown so as not to 
be mere toys, but scientific instruments, capable of ascending 
to great heights, remaining steady in currents of varying velocity, 
and of being manipulated with ease and rapidity by the observer, 
—The meteorology of Mozufferpore, Tirhoot, 1881, by Charles 
N. Pearson, F.M.S. 
Institution of Civil Engineers, November 14.—The pre- 
sident, Sir W. G. Armstrong, C.B., F.R.S., in the chair.—The 
paper read was on ‘Recent Hydraulic Experiments,” by Major 
Allan Cunningham, R.E., Honorary Fellow of King’s College, 
London. 
BERLIN 
Physical Society, October 3.—Prof. Rceber in the chair.— 
Dr. Kcenig had already reported in a previous session on the 
Leukoscope, designed and constructed by Prof. Helmholtz, and 
communicated now the results of his further experiments with 
this instrument. It consists essentially of a calc-spar-rhomboid, 
a plate of quartz, and a Nicol’s prism. A luminous pencil 
entering the calc-spar is split up into two rays polarised at right 
angles which traverse the quartz-plate and the Nicol. When 
spectroscopically analysed, these rays show two spectra of 
absorption-bands, in the spectrum of the one pencil at points 
where in the spectrum of the other pencil the intensity is 
undiminished, and vice versa, so that the two spectra super- 
posed would give a continuous spectrum. The number of 
bands increases with the thickness of the quartz, and they are 
shifted by rotating the Nicol. The modus operandi then is to 
put ina quartz plate of such a thickness, and to rotate the Nicol 
so much that in each of the spectra the colours tkat are not 
blotted produce together white light. When different sources 
of light are examined with the leukoscope, the different amounts 
of rotation of the Nicol are required for effecting a conformity 
of the two images, the relative quantity of certain rays being 
different in every different light, the prevailing tint belonging 
therefore to the one, and not to the other spectrum, Further 
experiments having proved that the plate of quartz could remain 
unaltered, the rotation angles of the Nicol were a gauge of the 
quality of colours of the light examined. Dr, Keenig has tried 
in this way a series of sources of light, and found the angles 
wanted for homogeneity of the white images to be as follows :— 
With stearin candles = 71°°20 ; with gaslight = 71°°5 ; with 
electric arc light = 79°; with magnesium light = 86° ; with 
solar light = 90°°5; with burning phosphorus and Drummond 
lime-light the angles were between gas and electric-are light. 
The succession of the sources of light thus stated coincides 
strikingly with the results of spectro-photometric measurements 
of Prof. Pickering. The fact that the magnesium light is more 
like the solar light than the electric are light quite corresponds 
with the known fact that of the aniline dyes, scarcely distin- 
guishable by gas-light, the greatest part can be perceived by 
electric light, but not all, viz. the so-called bronze hues ; whereas 
by the magnesium light they are all as well distinguished as by 
solar light. Furthermore Dr. Koenig has made many measure- 
ments with the leukoscope on different electric incandescent 
lights ; with Swan’s lamp and Edison’s lamp he gave the results 
of his experiments in tables in which the strength of the current, 
the intensity of ligbt, and the angles of the leukoscope were 
indicated. From these numbers it follows that luminosity aug- 
ments at first at a much greater rate with increasing st rength of 
current than the latter ; by doubling the strength of the current 
