ENS 
NADTORLS 
[ APRIL 4, 1907 
and Haschek gave a strong line of europium at A 4435-75. 
A search for other strong europium lines in the Arcturus 
spectrum revealed several abnormally strong stellar lines 
agreeing closely in position with the europium lines, and 
the author concludes that these cannot be explained with- 
out involving the rare element in question. Incidentally, 
he reviews the evidence for the occurrence of the same 
element in the sun’s chromosphere, and confirms Prof. 
Dyson’s previous conclusions that europium is represented. 
January 31.—‘ On the Discharge of Negative Electricity 
from Hot Calcium and from Lime.”’ By Dr. Frank 
Horton. Communicated by Prof. J. J. Thomson, F.R.S. 
This paper contains an account of some experiments in 
which the negative leak from hot calcium was compared 
and from lime under similar 
with that from platinum 
conditions. The negative leak from a platinum strip 
heated by an electric current was first investigated. This 
strip was then covered with metallic calcium by sublim- 
ation from an electrically-heated calcium wire situated in 
the discharge tube near to the kathode. The negative 
leak from the calcium-covered strip was determined at 
different temperatures. Some pure oxygen was then let 
into the apparatus, and the calcium on the kathode was 
oxidised to lime. The excess of oxygen was then removed 
and the negative leak again measured. Finally, hydrogen 
was let into the apparatus, and the effect of this gas on 
the negative leak trom lime was investigated. 
The results obtained may be summarised as follows :-— 
(1) The negative leak from calcium is greater than from 
platinum at the same temperature. 
(2) On oxidising the calcium on the kathode to lime 
there is a great imcrease in the negative leak. This is 
contrary to expectation, for we should expect the presence 
in the molecule of lime of the electronegative atom of 
oxygen to act as an attracting force tending to retain 
the escaping corpuscle, and that consequently the leak 
from lime would be less than from calcium under the 
same conditions. 
(3) The negative leak from lime in hydrogen is 
greaier than that in air or helium. 
much 
February 28.—‘ The Occlusion of the Residual Gas by 
the Glass Walls of Vacuum Tubes.’”’ By A. A. Campbell 
Swinton. Communicated by Sir William Crookes, 
E.R ES: 
On strongly heating portions of the glass walls of 
vacuum tubes that had been subjected to severe use in 
1898, and had since lain open to atmospheric pressure, 
they immediately became clouded, the effect being due to 
quantities of minute spherical bubbles of gas which could 
be clearly seen with a microscope, and were on the 
average about 0-01 mm. in diameter. By dissolving away 
one surface of the glass with hydrofluoric acid until the 
bubbles just disappeared, and measuring the thickness 
before and after this process, it was ascertained that the 
bubbles were about 0-122 mm. from the inner surface of 
the glass. It would therefore appear that the particles 
of gas must have been shot into the glass to about this 
depth. 
In a typical case the number of bubbles per square 
centimetre was found to be about 625,000, from which it 
was calculated that the total amount of gas at atmo- 
spheric pressure occluded in the particular tube was nearly 
0-05 cm. apart from any further amount that may have 
escaped on the heating of the glass. 
A number of pieces of the glass were next placed in a 
flat and air-tight tin chamber connected with a vacuum 
pump and a spectrum tube. This was exhausted until 
no electric discharge would pass through the spectrum 
tube, and was then hammered so as to powder the glass. 
There was an immediate fall of vacuum, and on examin- 
ation with a spectroscope the gas that had been evolved 
was found to be mainly hydrogen. This process was 
repeated several times, the result in each case being to 
bring out more hydrogen. It would therefore appear that 
the gas occluded in vacuum tubes exhausted in the ordinary 
manner from atmosphere is almost entirely hydrogen, 
due, no doubt, to the electrolysis of water vapour. 
Further experiments were tried with helium. A new 
tube was first exhausted until no discharge would pass, 
NO. 1953. VOL. 75] 
and then helium was admitted in small quantities from 
time to time with intervening sparking, until 1 cubic 
centimetre at atmospheric pressure had been absorbed. 
The glass of this tube showed bubbles when heated, and 
on placing some of it in a vacuum chamber, as before 
described, and reducing it to powder, sufficient helium 
was evolved to show the helium spectrum clearly. See- 
ing that helium does not combine with anything at 
from the glass by mere mechanical powdering of the 
latter, it would appear that the occlusion is due to the 
mechanical driving of the gas into the glass, and not to 
any chemical combination. 
Linnean Society, March 7.—Prof.W. A. Herdman, F.R.S., 
president, in the chair.—A series of specimens of Nitella 
ornithopoda, A. Braun, collected by the Rev. Canon Bullock 
Webster: H. and J. Groves. This rare species has only 
been found in a small district in the west of France, from 
Angouléme in the north to the south of Arcachon, and 
doubtfully in one locality in Portugal. The especial interest 
of the specimens exhibited, which were collected to the 
south of Arcachon in March and April, 1906, was that they 
represented gatherings of the plant from very different 
habitats, and showed great variations. The plants collected 
in shallow ditches were already in full fruit, while those 
from. running water and from Lake Cazan were quite 
immature, and so far sterile. Only a few specimens of this 
species have previously reached England, and the collection 
exhibited was probably by far the most extensive series of 
forms yet obtained.—The ornamentation of the frog tad- 
pole, Rana temporaria, tracing the growth of golden spots 
which attain a maximum about the thirtieth day after the 
tadpole emerges from its gelatinous envelope: Miss N. F. 
Layard.—Decapoda captured during the 1900 cruise of 
H.M.S. Research in the Bay of Biscay, forming No. xi. of 
the series of reports: S. W. Kemp. The majority of the 
specimens were larval, adult Decapoda, being as a rule 
strong enough to swim out of an ordinaty tow-net. A fine 
series of stages of Acanthephyra purpurea, A. M.-Edw., 
showed that, as Coutiére predicted, this species hatches as 
a Zoza, while the allied A. debilis leaves the egg in a 
“ post-larval” condition, with all its appendages formed. A 
curious feature of development was noted in that the ros- 
trum and cornea, after considerable growtn, undergo a 
sudden reduction, followed again by subsequent growth to 
the adult condition. The various stages, and those of a 
Caricyphus larva, were fully described and figured.—Colour 
changes in South African chameleons, observed during the 
visit of the British Association to South Africa in 1905: 
Prof. E. B. Poulton and Dr. G. B. Longstaff.—The occur- 
rence of Spergularia atheniensis and Agrostis verticillata in 
the Channel Islands: G. C. Druce. 
Geological Society, March 13.—Dr. Aubrey Strahan, 
F.R.S., vice-president, in the chair.—A Silurian inlier in 
the eastern Mendips: Prof. S. H. Reynolds. The frag- 
mental igneous rock is of two types :—(1) normal fine- 
grained tuff, from which in three localities more than 
thirty species of Silurian (probably Llandovery) fossils 
have been identified; the tuffs are seen at Sunnyhill to 
underlie the trap; (2) a coarse ashy conglomerate, the 
relation of which to the other rocks is obscure. Four 
possibilities as to the nature of this rock are discussed. 
It may be the basement-conglomerate of the Old Red 
Sandstone, an aqueous deposit belonging to the same 
igneous series as the associated trap and normal tuff, or 
an old river-gravel deposited subsequent to the fossiliferous 
Silurian and prior to the Old Red, or it may represent the 
necks of the voleanoes from which the rocks were ejected. 
The last of these possibilities agrees best with the facts.— 
Changes of physical constants which take place in certain 
minerals and igneous rocks, on the passage from the 
crystalline to the glassy state, with a-short note on eutectic 
mixtures: J. A. Douglas. The author describes the 
electrical apparatus employed. Powdered rock of known 
specific gravity is fused as often as required in a loop 
of platinum ribbon. The fused product is powdered, ex- 
amined with the microscope, and then placed in a diffusion 
column. The diffusion column is sealed in a glass tube. 
; Acid rocks were found to increase 6 per cent. to 10 per 
ordinary temperatures, and that this gas was extracted 
‘ 
