648 
NATURE 
[May 12, 1923 

conductivity found in many metals when cooled 
nearly to the absolute zero of temperature. 
WEATHER RESEARCH ON THE KERMADEC ISLANDS. 
—The New Zealand Journal of Science and Technology, 
vol. v. No. 5, contains an article by Mr. D. C. Bates, 
director of the Dominion Meteorological Office, 
Wellington, on the above. The chief feature of the 
article is an effort to stimulate the acquiring of 
Sunday Island, the largest of the Kermadec Group, 
for a meteorological station, which it is maintained 
would improve the weather forecasting for New 
Zealand. It is shown that cyclonic disturbances 
commonly influence the weather at Sunday Island 
a couple of days or so before being felt in New Zealand 
or the adjacent waters. The island was first dis- 
covered in 1788 and was partially frequented by 
settlers in 1837, but calamities which have occurred 
suggest the question whether it is worth while 
occupying apart from weather reporting. The island 
is apparently of volcanic origin, and earthquakes 
occur about once a month. It is mountainous, with 
few flat surfaces; water is not easily procurable, 
and it is out of the track of vessels. The rainfall is 
said to be by no means deficient. Meteorological 
observations taken for nine months in 1908 show a 
total rainfall of 66°26 in. during the period; the 
heaviest monthly fall was 11°30 in. during April, 
the least, 3°91 in. during September. The highest 
temperature in the shade was 85° F. in February, the 
lowest 46° F. in August. Easterly winds predominate 
from February to May, and westerly winds from June 
to October. No observations are available for 
November, December, and January. 
Tue DeEbAy oF VisuAL PERCEPTION.—The issue 
of the Optician and Scientific Instrument Maker for 
April 20 contains an article by Mr. F. G. Smith which 
summarises the recent work of Prof. Piilfrich on the 
effect of brightness on the time which elapses between 
the formation of an image on the retina and its 
perception by the observer. If an object moving 
across the line of vision from left to right is viewed 
with the right eye direct and with the left through a 
smoked glass to diminish the brightness of the image 
formed on the left retina, there is a delay in perception 
in the case of each eye, but the delay for the left eye 
exceeds that for the right, and the body appears to 
the left of and behind the actual position it occupies. 
If the object is moving from right to left it appears 
for the same reason to the right and in front of the 
actual position. If it moves alternately to right and 
left it appears to describe a circular motion about its 
mean position, The experiment is easily done with 
a fixed and a moving pencil, and it is rather remark- 
able that the phenomenon has not been observed 
previously. 

BrivTIsH SURVEYING INSTRUMENTS.—Several recent 
improvements in the design and construction of 
British-made surveying instruments are detailed and 
illustrated in a paper by W. H. Connell in the Pro- 
ceedings of the South Wales Institute of Engineers, 
vol. xxxix. No. 1, March 15, 1923, which has been 
reprinted in pamphlet form by Messrs. Cooke, 
Troughton and Simms, Ltd., Buckingham Works, 
York. Modern manufacturing methods involving 
the extensive use of jigs render possible the attain- 
ment of great accuracy and uniform production of 
the parts of instruments. The use of new and 
improved alloys has diminished the wear of moving 
parts, and thus instruments retain their adjustments 
for longer periods. Changes in design have led to 
the elimination of many adjustments, only one being 
necessary or provided in many modern levels, namely, 
NO. 2793, VOL. 11T] 


that for securing parallelism between the line of sight 
and the tangent to the curve of the bubble tube. By 
the adoption of the internal focussing telescope 
collimation errors are almost entirely eliminated, 
and the use of accurately fitting removable cells 
permits of the graticules being cleaned or exchanged __ 
without disturbing the collimation adjustment. 
Changes have been introduced also with the view of 
saving time and labour in ‘taking readings. For, 
example, the bubble, compass, and staff can all be 
read from the eye-end of the telescope without change 
of position on the part of the surveyor, and the 
focussing screw is easily accessible no matter what 
position the telescope may be in. 
LITHIUM CARBIDE AND HypDrIDE.—In the Comptes 
vendus of the Paris Academy of Sciences for April 9 
MM. A. Guntz and Benoit give an account of some 
properties of a mixture of lithium carbide and lithium 
hydride. This homogeneous mixture can be obtained 
either by heating metallic lithium in ethylene or by 
dissolving lithium carbide in fused lithium hydride. 
Submitted to electrolysis this fused mixture gives an 
abundant deposit of amorphous carbon. This may 
arise from a true electrolysis of the carbide or by a 
secondary reaction between hydrogen from the 
electrolysis of the hydride and the lithium carbide. 
From the results of their experiments the authors 
are inclined to regard the first view as the correct 
one, the lithium carbide being ionised into its elements 
in the hydride solution. The minimum electromotive 
force required to produce the carbon deposit is about 
0°05 volt. 
VULCANISATION OF RuBBER.—Mr. V. V. Byzoy, in 
the Journal of the Russian Physical and Chemical 
Society, 1921, vol. 53, gives an account of work he 
has carried out on the vulcanisation of rubber. The 
researches indicate that the processes of hot and of 
cold vulcanisation are essentially the same, and are 
of extreme complexity. Vulcanised rubber consists 
of four components, which may’ exist in varying 
proportions in different samples of rubber. The first 
component is crystalline sulphur, which can be ex- 
tracted from the rubber by boiling acetone. In a 
specimen of rubber containing 2°86 per cent of sulphur, 
1°57 per cent was of this type. Most of the remaining 
sulphur is adsorbed in the rubber, and is in the 
amorphous plastic condition, this form of sulphur 
being insoluble in acetone. While plastic sulphur, 
under ordinary conditions, soon crystallises, in the 
fine state of division in which it occurs in rubber, 
conditions are perfect for supercooling, as each 
globule of sulphur is enclosed in a protective coat of 
colloidal material. To this plastic sulphur is ascribed 
the superior elasticity of vulcanised rubber. The 
rubber itself undergoes isomeric change to an in- 
soluble form, from which a hydrochloride more stable 
than that obtained from ordinary rubber may be 
prepared, and the ozonide of which gives, on hydrolysis, 
not levulinic aldehyde, as does that of natural rubber, 
but diacetyl propane. Whether this difference is 
due to a different degree of polymerisation of the 
isoprene molecules, or whether a transposition of the — 
double linkages has occurred, it is not possible 
definitely to state. 
sulphide [C,,H,,S2]n, but this is not as a rule present 
to any great extent. Thus vulcanisation of rubber 
is not a reversible process, and the problem of the ~ 
recovery of pure rubber from an already vulcanised — 
material, important in the waste rubber utilisation 
industry, appears to be an impossible one, as no means 
are known whereby the insoluble isomeride of rubber _ ; 
can be converted into the natural form. 
~ 
The fourth constituent of 
vulcanised rubber is a polymorph of isoprene di- 
