306 
whether the photographic plate remains an absolutely accurate 
picture of the actual relative positions of the stars in the sky itself, 
and, moreover, whether these are measurable with that extreme 
degree of precision which is attainable with the best instrumental 
means. To ascertain this, the same plates for a portion of the 
Pleiades were taken which gave rise to the formula already 
obtained. The distances of some twenty-five of the stars from 
Alcyone were measured an each of these plates, the number of 
repetitions of the measures being made the same as those 
adopted by Bessel in his measures of the same distances with 
bis heliometer. The resulting accordances of these individual 
measures on each of the plates was very satisfactory, and a trifle 
better than the accordances in the case of Bessel’s measures ; 
and the accordance of each of the means of the distances of each 
of the stars from Alcyone on each plate was at least quite equal 
to the results obtained with the heliometer. The average devia- 
tions from the mean for all the measures was, in the case of the 
photographic plates, 0°24, and, of the heliometer measures, 
o”:29. ‘These satisfactory accordances of the resulting measures 
on each of the plates (corrected for refraction, and where neces- 
sary for aberration), afford a sure indication of the reality of 
the pictures, as well as of their accurate measurability. 
An interesting circumstance occurred in the course of the 
work. On one of the plates the distances of three stars from 
Alcyone exhibited a slight discordance of from o""75 to 1'°5, 
when compared with those stars on the other plates. These 
three stars all occupied a small area on the plate; no discord- 
ances occurred on this plate with respect to any of the other 
stars. Here is an indication of a slight disturbance of the film 
on one small portion of the plate, but on no other portion. 
Hence the necessity of the precaution of taking at least three 
plates for the purpose of security of measurement. The plates 
were exposed variously for about 8 to 12 minutes in the focal 
plane of the de la Rue reflector of 13 inches aperture, 
(3) A few stars were examined on the same plate with 
different exposures, varying from I second to 120, with the view 
of ascertaining, if possible, the relation between the areas of the 
impressed star-disks and their time of exposure. As far as at 
present appears, these areas vary as the square root of the time. 
This result differs widely from that obtained by Bond in 1858. 
That astronomer considered that these areas varied directly as 
the time; the investigation, however, is not yet complete, and 
will be resumed at Oxford. It is well known that these photo- 
graphic disks are not sharply and definitely cut circles on the 
negative plate, when examined with the higher powers of the 
microscope, such as 100 and beyond ; but they are fringed with 
a number of discreet black dots extending to some distance 
beyond the hard photographic images. ~ Nevertheless, these 
images, when printed in the form of position, lose this fringe, 
and present the appearance of well-defined sharply-cut circles ; 
the light appears to have penetrated through the interstices of 
the discrete fringe, and leaves a very definite outline. En- 
couraged by these results of the measurements of the stars from 
Alcyone, I propose to test this photographic method still further 
by applying it, not without hope of success, to the question of 
stellar parallax. 
These measures are now well advanced, and afford good hope 
of success. 
Chemical Society, June 17.—Dr. Hugo Miiller, F.R.S., 
President, in the chair.—The following were elected Fellows of 
the Society:—Thomas Akitt, James Blake, M.D., Alfred 
Chaston, A. W. H. Chapman, Augusto Cesar Diojo, Charles 
A. R. Jowitt, Charles Alexander Kohn, John Temple Leow, 
William Ray, Joseph Price Remington, William Richards, 
Forbes Rickard, William Saunders, Charles A. Smith.—The 
following papers were read :—The electrolysis of aqueous solu- 
tions of sulphuric acid, with special reference to the forms of 
oxygen obtained, by Prof. H. McLeod, F.R.S.—Essential oils 
(Part II[.): their specific refractive and dispersive power, by 
Dr. J. H. Gladstone, F.R.S.—The formation and destruction 
of nitrates and nitrites in artificial solutions and in river and 
well waters, by J. M. H. Munro, D.Sc.—Water of crystallisa- 
tion, by W. W. J. Nicol, M.A., D.Sc., F.R.S.E.—A method 
of investigating the constitution of azo-, diazo-, and analogous 
compounds, by R, Meldola, F.R.S., and F. W. Streatfeild.— 
The estimation of free oxygen in water, by Miss K. I. Williams 
and Prof. W. Ramsay.—Note as to the existence of an allo- 
tropic modification of nitrogen, by Miss K. I. Williams and 
Prof. Ramsay.—The presence of a reducing agent, probably 
WA TORE 
[ Fuly 29, 1886 
hydrogen peroxide, in natural water, by Prof. Ramsay. —Evapo- 
ration and dissociation (l’art IV.); a study of the thermal 
properties of acetic acid, by W. Ramsay, Ph.D., and Sydney 
Young, D.Sc.—Note on the vapour-densities of chloral ethyl- 
alcoholate, by William Ramsay, Ph.D., and Sydney Young, 
D.Sc.—The nature of liquids as shown by a study of the 
thermal properties of stable and of dissociable bodies, by 
William Ramsay, Ph.D., and Sydney Young, D.Sc.—The 
electromotive forces developed during the combination of cad- 
mium and iodine in presence of water, by A. P. Laurie, B.A., 
B.Sc.—Detection and estimation of iodine, bromine, and 
chlorine, by M. Dechan.—The analysis of alloys and minerals 
containing the heavy metals, selenium, tellurium, &c., by 
Thomas Bayley. 
Entomological Society, July 7.—Mr. J. Jenner Weir, 
F.L.S., Vice-President, in the chair.—Mr. S. H. Scudder, of 
Cambridge, Mass., U.S., was elected a Foreign Member of the 
Society.—The Rev. H. S. Gorham exhibited specimens of 
Eucnemis capucina, Ahr , a species new to Britain, discovered 
in June last in an old beech tree in the New Forest. He also 
exhibited specimens of Casstda chloris.—Dr. Sharp exhibited 
larvee of JZe/oé, and read notes on their habits, and Mr. Saunders 
exhibited a specimen of Hadécius infested with about thirty AZe/oé 
larvee. Mr. Billups remarked that he had recently found forty- 
seven larve of JZe/oé on the body of a species of Aucera. Dr. 
Sharp said that he was of opinion that the operations of these 
larvee were not the result of instinct, but were more like reflex 
actions : the instant the larvee touched a suitable surface they 
clung to it. The discussion was continued by Prof. Riley, who 
disagreed with Dr. Sharp, and believed these larvae were guided 
by instinct, as they showed a decided preference for particular 
hosts.—Mr. Jenner Weir exhibited a male of Lycena bellargus 
and a female of Z. zcaras, which had been captured 2 copula by 
Mr. Hillman, and shown to the exhibitor at the time of capture. 
Mr. Weir also exhibited some specimens of Zycena which he 
believed to be hybrids between Zi cena bellargus and L. tcarus ; 
and he further exhibited, on behalf of Mr. Jenner, four speci- 
mens of Phosphenus hemipterus, taken at Lewes.—The Rev. 
W. W. Fowler exhibited two specimens of Cirysomela cerealis, 
lately taken by Dr. Ellis on Snowdon ; and also two specimens of 
Actocharis Readingit, found at Falmouth by Mr. J. J. Walker.— 
Mr. E.B. Poulton called attention to the fact that the larvee of some 
Lepidoptera, if fed in captivity on an unusual food-plant, subse- 
quently refused to eat their ordinary food-plant. He stated that 
he had observed this with the larvae of Pygera bucephala and 
Smerinthus ocellatus. Mr. Stainton, Mr. Fowler, and Mr. Goss 
made some remarks on the subject.—Mr. Elisha exhibited a 
series of bred specimens of Geometrva smaragdaria.—M. Alfred 
Wailly exhibited a long series of silk-producing moths, including 
some remarkable hybrids between P. cecropia and P. ceanothi ; 
and Prof. Riley and Mr. Weir made some observations on these 
hybrids.—Dr. Sharp read a paper on Eucnemis capucina (Ahr.) 
and its larva.—Mr. Dunning read a report on the subject of the 
importation of humble-bees into New Zealand, from which it 
appeared that the efforts of Mr. Nottidge, of Ashford, and the 
Canterbury (N.Z.) Acclimatisation Society had been successful, 
and that the long wanted clover-fertiliser had at length been 
| established in New Zealand.—M. Peringuey communicated notes 
on some Coleopterous insects of the family Pausside.—Mr. J. 
B. Bridgman communicated additions to the Rev. T. A. Mar- 
shall’s Catalogue of British Ichneumonidee.—Prof, Riley read 
notes on the phytophagic habit, and on alternation of genera- 
tion, in the genus /sosoma. In this paper Prof. Riley described, 
from direct observation, the phytophagic habit in two species of 
the genus. He also established the existence of alternation df 
generation. 
EDINBURGH 
Royal Society, July 5.—The Hon. Lord Maclaren, Vice- 
President, in the chair.—In a paper on the electrical resistance 
of niekel at high temperatures, Prof. C. G. Knott, of Tokio 
University, gave an account of experiments on certain nickel 
wires, in which the temperature was carried to a fairly bright 
red head. The resistance at different temperatures was com- 
pared with the resistance of a platinum wire at the same tem- 
peratures ; and, by the substitution of other metals for the 
nickel, further comparisons were established. Nickel, platinum, 
palladium, and iron were thus studied; and the general con- 
clusions were as follows :—(1) The rate of growth of the resist- 
