the best years of their youth and manhood to acquiring a com- 
petent knowledge of the science of their subject, unless they (the 
evening students of this country) had, as the leaders of their in- 
dustries, men of an equal training to that of their competitors. 
The general tendency of Prof. Meldola’s remarks was to en- 
courage more concentrated effort on the part of such large urban 
districts as Barking, East Ham, Dagenham, and surrounding 
parishes, which contain a population of some 40,000 people, and 
he expressed the hope that the local committees would see their 
way to federation and joint action in the carrying on of organised 
day classes, as well as the evening work upon which they had 
hitherto concentrated their efforts. At the conclusion of the 
address the Countess of Warwick, in a short and forcible speech, 
also urged the importance of organised day work, and endorsed 
the wish expressed by Prof. Meldola that Barking would be in 
possession of such schools at no very distant period. Mr. W. 
Bewers, to whom the success of the Barking School is so largely 
due, and who is chairman of the local committee, presided at 
the meeting. 
SOCIETIES AND ACADEMIES. 
LONDON. 
Physical Society, November 13. — Captain Abney, 
President in the chair.—A paper on some experiments with 
Rontgen’s radiation, by Prof. Threlfall and Mr. Pollock, was, 
in the absence of the authors, read by the Secretary. —The 
authors describe a form of Crookes’ tube which, while it can be 
made by any one capable of the most elementary glass-blowing, 
gives a plentiful supply of R6ntgen rays. The results of their 
experiments may be summed up as follows: (1) The Rontgen 
radiation does not consist in the projection of gaseous matter, 
or, if it does, the amount of such matter involved is extra- 
ordinarily small. (2) The Rontgen radiation does not consist 
in the projection of zther streams having a velocity above a 
couple of hundred metres per second ; this is true, whether the 
radiation takes place in air or in benzene. (3) The properties 
of the ether regarded as determining the velocity of electro- 
magnetic waves are not greatly changed (z.e. not at all within 
‘our experimental limits) by the Rontgen radiation; and this 
applies alike to the ztherinair and in benzene. (4) Aselenium 
cell composed of platinum electrodes and highly purified 
selenium, is affected by Rontgen radiation to an extent which is 
comparable with the effect produced by diffused daylight. (5) 
No permanent or temporary electromotive force is set up in a 
selenium cell by the Réntgen radiation. The authors have 
come to the first conclusion by exposing an exhausted tube placed 
in parallel with a spark-gap, so adjusted that the spark just passes 
over the gap rather than through the tube, to the Rontgen 
radiation. They find that a vacuum tube in parallel with a 
spark-gap is very sensitive to changes in pressure within the 
tube. Conclusions (2) and (3) were arrived at by using 
Michelson’s arrangements for the interference 6f two beams of 
light. Mr. Shelford Bidwell said he had made some experi- 
ments on the effect of Rontgen rays on the resistance of selenium, 
but with a negative result, although he would have detected a 
much smaller change than that found by the authors. It might 
be that this difference was due to the tube, for, in his experi- 
nent, the radiation started from a platinum plate within the 
iube, while in the authors’ arrangement the radiation starts from 
where the kathode rays strike the glass of the tube. Prof. 
Silvanus Thompson said there were a number of points with 
reference to the Rontgen radiation which required clearing up. 
For instance, the suggestion that they were vortices in the zther 
had not been tested. Again, Lafay says that if the rays are 
passed through a metal screen which is charged with electricity, 
then the rays can be deflected by a magnet. He (Prof. 
Thompson) had not been able to repeat this experiment, neither 
had he that of Galitzine on the polarisation of the rays by tourma- 
line. The statement of Prof. J. J. Thomson, that under the 
influence of the radiation paraffin became a conductor, had not 
been satisfactorily proved. As to the wave-length, while 
some observers obtained values about one-tenth that of the 
extreme violet, another had obtained a value greater than that 
of the extreme red. He (the speaker) did not understand the 
authors’ device for detecting changes in the vacuum of a tube, 
since every one who has worked with Crookes’ tubes has found 
that the resistance is always greater for a spark in one direction 
than the other, and also varies with the battery power employed. 
Lenard, adopting Hertz’s arrangement, uses as anode a cylinder 
NO. 1412, VOL. 55] 
NATURE 
[| NOVEMBER 19, 1896 
surrounding the kathode (a disc), the idea being that by using 
such a symmetrical arrangement the kathode radiation was more 
homogeneous. It might be advisable, when seeking to produce 
homogeneous Réntgen rays, to adopt such a symmetrical 
arrangement.—Mr. Bryan then read a paper, by himself and Dr. 
Barton, on the absorption of electrical waves along wires by a 
terminal bridge. The authors employ, for the generation of the 
oscillations, an arrangement of the same description as that used 
by Bjerknes, the waves being propagated along two parallel 
wires about 116 m. long. In order to measure the waves, they 
use a small electrometer with an uncharged needle. The 
resistances employed to form the bridge consist of pencil-marks 
on ground glass. Bridges of three resistances have been 
examined, one having, as nearly as may be, the resistance 
necessary, according to Heaviside’s theory, to give complete 
extinction of the reflected wave, and, of the others, one was of 
higher, and the other of lower resistance. In each case the 
results confirm the theory, and it is thus experimentally proved 
that by using a bridge of this description the reflected train of 
waves can be completely extinguished. Mr. Blakesley asked if 
the authors had made any allowance for the capacity of the 
wires. Mr. Campbell asked if the resistances given were 
expressed in ohms or in electro-magnetic units. Mr. Bodwell 
asked if the authors had found that the pencil-trace resistances 
obeyed Ohm’s law. He had found that if you balanced with 
one cell in the battery circuit, then, on increasing the battery 
power to two cells, the resistance altered. Mr. Appleyard 
suggested that the variation was caused by the contacts at the 
ends not being good. Mr. Campbell said the same variation 
occurred in the case of mixtures of clay and plumbago, where 
the contacts were quite good. Mr. Carter suggested electro- 
plating the ends to give good contact. Mr. Bryan, in his reply, 
said that they had not considered the question of capacity, and 
that, in their case, they did not require to know the resistance 
very accurately. 
Entomological Society, November 4.—Prof. Raphael 
Meldola, F.R.S., President, in the chair.—Mr. McLachlan 
exhibited a collection of the cast nymph-skins of more than 
one-third of the species of European dragon-flies from the 
Département de l’Indre, France, sent to him by M. René 
Martin. Two or three of the species had been reared in 
an aquarium, but the identification of most of them had been 
secured by finding the imago drying its wings in the immediate 
vicinity of the cast skin. —Mr. R. Adkin exhibited a long series 
of Acedalia marginepunctata taken on the sea-coast at East- 
bourne, Sussex, during the past eight summers.—Mr. Horace 
St. Tohn Donisthorpe exhibited a female specimen of Dytzsces 
circumcinctus, Ahr., with elytra resembling in form those of 
the male. He said the specimen had been taken in Wicken 
Fen in August last.—Mr. Tutt exhibited a specimen of AZed/znia - 
ocellarés recently taken near Southend, together with a specimen 
of J/. gilvago for comparison ; also four specimens of Argy- 
resthia atmortella taken by Mr. Atmore last June at Lynn, 
Norfolk. Mr. Tutt also exhibited a long series of a I/edampias 
which he had captured at Le Lautaret in the Deuphiné Alps, 
at an elevation of 7000-8000 feet. He observed that the 
specimens exhibited were peculiar in some very important 
particulars, combining some of the characteristics of Erebza 
(Melampias) melampus, and M. pharte. He said his attention 
had been first drawn to this form by some fine examples captured 
by Dr. Chapman and himself on Mont de la Saxe in 1895. 
Compared with the Tyrolean examples of JZ me/ampus, this, 
form showed a tendency to a lengthening of the forewings and 
to an obsolescence of the black dots, thus approaching JZ. pharte, 
but the females presented none of the typical characters of the 
female of 1/7. pharte. On the whole, he felt satisfied that the 
Mont de la Saxe specimens were a form of J/. melampus. 
Mr. Elwes observed that though all the continental butterflies 
had been so long studied by European entomologists, he did 
not think the form exhibited by Mr. Tutt had béen hitherto 
noticed. —Mr. E. Ernest Green exhibited a typical specimen of 
Ephyra omicronarta, together with what he believed to be a 
remarkable melanic variety of the same species, taken by 
Dr. Dudley Wright at Pegwell Bay, near Ramsgate, in 
September last. Some of the Fellows present, after an examina- 
tion of the specimen, expressed an opinion that it was a variety 
of an Acidalia, and not of Zphyra omicronaria. 
Anthropological Institute, November 10.—Mr. E. W. 
Brabrook, President, in the chair.—Mr. P. L. Sclater exhibited 
adraught-board from Nyasaland; Mr. C. H. Read, a dance-mask 
