—— 
——— 
DECEMBER 14, 1916] 
another taken at the Lick Observatory in 1913; also in 
a photograph taken at Allegheny at) Mr. Hubble’s 
request. The most striking change was what at first 
appeared to be a transverse shift of a bright patch 
just north. of the nucleus, but further examination 
suggested that this was more probably. due to the 
sudden appearance of a mass of bright nebulosity. 
There are several other differences between the photo- 
graphs which appear to be due to real changes in the 
nebula. In particular, a small mass a little south- 
east of the nucleus exhibits a decided irregular move- 
ment, having moved in towards the nucleus when the 
above-mentioned new mass appeared. This small 
mass moved not less than 0-5” per year between 1908 
and 1913, and it seems likely to have a measurable 
parallax. 
Rotation of the entire nebula would not account for 
the variations observed, but some of the changes may 
be explained by local brightening and fading of sta- 
tionary matter. Actual motion of portions of nebu- 
losity relative to the nebula as a whole, however, is 
regarded by Mr. Hubble as the probable explanation 
of most of the changes observed. The spectrum of 
the nebula has been found to be. continuous. 
THE STRUCTURE OF THE RED LitHium Linr.—The 
complex structure of the red line of lithium, A 6708, has 
been -further investigated by Dr. A. S. King at the 
Passadena Laboratory (Astrophysical Journal, vol. 
xliv., p. 172). It is shown that the line may appear 
with two distinct sets of components, either as an 
unsymmetrical doublet, or as a triplet of variable 
separation. In a third stage the side components of 
the triplet change into an ordinary reversal within 
which the central component can still be seen. All 
three conditions of the line may be produced either in 
the are or electric furnace, and the controlling agency 
appears to be the amount of vapour in the source. 
The variable interval of the components suggests an 
electrical resolution, which would most likely be due 
to the action of interatomic fields. The observations 
have proved that the line at 6708 which commonly 
appears in calcium spectra is due to lithium impurity. 
Also, it may now be considered certain that the strong 
line appearing at this position in the spectra of sun- 
spots should be attributed to lithium. It is remark- 
able that this should be the only direct proof of the 
presence of lithium in the sun, there being no repre- 
sentatives of this element in the Fraunhofer spectrum. 
PLANTATION RUBBER.. 
THs Trade Supplement of the Times for December 
is devoted almost entirely to plantation rubber. 
The editor has drawn upon some of the best authori- 
ties in the plantation’ world for his contributions, and 
without exaggeration has achieved a pronounced suc- 
cess. The articles deal with the development of the 
plantation rubber industry throughout the Middle 
East, the physical, biological, and chemical problems 
involved in the preparation of the raw material, and 
the importance of the supplies to the manufacturing 
industry in this and every other country. 
The large number of contributors has resulted in 
repetition of the same facts, but this was scarcely 
avoidable in such an issue. Much of the information 
has already been disseminated in text-books and tech- 
nical journals, but the matter has been rendered in 
this supplement in a form which will appeal to all 
interested in the industry either financially or tech= 
nically. 
In one of the most important articles Prof. J. Bret- 
land Farmer outlines the risks of tropical agriculture, 
the efforts which have been made by Government and 
private individuals, and the need for still greater pre- 
NO. 2459, VOL. 98} 
NATURE 
299 
caution and the placing of the industry on a better 
scientific foundation. It is already known that the 
Imperial College of Science has sent a number of 
scientific officers to the Middle East, and we know 
from personal contact with them that they have felt 
the necessity of periodically spending a part of their 
time in first-rate laboratories in Europe or America. 
It is impossible for the scientific officers in charge of 
plantations in the Middle East to be conversant with 
all the advances made in plant sanitation, biological 
problems, and testing apparatus of value to the planta- 
tion industry 
A brief survey of the article on ‘Pests and 
Diseases,” by Mr. J. Mitchell, satisfies one that there is 
every reason why the many diseases affecting the roots, 
bark, stems, and fruits of Hevea brasiliensis should 
be carefully watched. The necessity for independent 
scientific officers to be put in charge of such work: is 
quite apparent even to the ordinary investor, who has 
but little knowledge of mycological and entomological. 
problems 
With regard to the physical and chemical researches: 
in the laboratories of the manufacturers, some very 
useful information is contributed by Mr. W. A. Wil- 
liams, Dr. Joseph Torrey, and Dr. Philip Schidrowitz. 
There is a great lack of uniformity in cultivated 
rubber, which materially affects processes of manu- 
facture and the finished article. It is suggested that 
the difficulties consequent on variation of plantation 
rubber can be reduced by standardisation of methods. 
of preparation on the estate and by closer co-operation 
with manufacturers in this country. The lack of co- 
operation between plantation growers and manufac- 
turers is emphasised by Mr. Alexander Johnston. 
A review of this supplement cannot be completed 
without reference to the very strong article by Mr. E. 
Stevenson, chairman of the Rubber Trade Association 
of London. Mr. Stevenson points out the absolute 
need of organisation, and shows that the growers 
themselves are very largely responsible for the com- 
petitive system which they have set up. Organisation 
is apparently as necessary among producers, manu- 
facturers, and dealers in raw rubber as it is on the 
plantations, and the supplement before us will serve 
a good purpose if it results in any definite advances 
being made in this direction. H.W. 
MARINE ISOPODA FROM THE NORTH 
ATLANTIC.! 
THE papers before us form two of the valuable 
series of reports now being issued by the Danish 
Government, through the Zoological Museum at 
Copenhagen, on the results of the exploration of thc 
deep sea in the neighbourhood of Greenland, Icelanv 
and the Far6ées. They constitute a monograph of th. 
Isopoda and Tanaidacea of that region, and their im- 
portance may be judged from the fact that, whereas 
previously only fifty-three species of Isopoda were 
known from the area surveyed, Dr. Hansen records 
242 species, of which 125 are described for the first 
time, and establishes eighteen new genera. This 
satisfactory result is due to the methods of collecting 
introduced by the author during the expedition. The 
mud brought up in the trawl and dredge was care- 
fully sifted through fine bolting silk, and the results 
of the sifting preservéd for future examination. In 
this wav hundreds of small animals, which could not 
have been collected by any other means, were dis- 
covered. This method may be recommended to 
naturalists in charge of future expeditions for the ex- 
1 “ The Danish /ngo//Expedition.” Vol. iii., No. 3, “Crustacea Mala- 
costraca,” II. By H. J. Hansen. Pp. r4s+r2 plates. (1913.) 
“The Danish /ngol//-Expedition.” Vol. iii., No. “Crustacea Mala- 
costraca,” III], Pp. 262+16 p'ates (Copenhagen: Printed by Banco 
Luno, 1919.) 
