192 
ducing a colour that is natural and permanent. 
The exhibition of Algz in the Botanical Gallery, 
which has been recently rearranged, shows an 
appreciable success for the red Algz and some 
satisfactory results for the brown Algz. It is pro- 
posed to present an account of these experiments 
shortly before one of the scientific societies. 
A. B. RENDLE. 
© 
DR. J. O. BACKLUND. 
PAPA OS ONERS will hear with regret of the 
death of Dr. Backlund at Pulkova on 
August 29. He was a native of Sweden, having 
been born at Langhem, in Wermland, on April 28, 
1846. He studied mathematics and astronomy 
at the University of Upsala, and in 1873 went to 
Stockholm Observatory as assistant to Prof. 
Gylden, whose new methods of perturbations he 
studied with enthusiasm. After a brief return 
to Upsala in 1875, he left Sweden for Russia, 
where he remained permanently. He was at 
Dorpat Observatory for three years, and in 1879 
went to Pulkova as assistant to Dr. Otto Struve. 
On Prof. Bredichin’s. death in 1895 he was 
appointed director of the Observatory, retaining 
this post until his death. 
Dr. Backlund is best known for his immense 
researches on the motion of Encke’s comet, for 
which he received the gold medal of the ‘Royal 
Astronomical Society in 1909. Encke had de- 
tected the acceleration in the comet’s mean motion, 
which he ascribed to the action of a resisting 
medium. After his death in 1865 von Asten took 
up the research, adopting some of Gylden’s 
methods. He was unable to represent the comet’s 
motion by any constant value of the acceleration, 
and died at Pulkova in 1878 without solving the 
problem completely. Backlund took up the 
matter, receiving grants from M. E. Nobel and 
the Petrograd Academy of Sciences for assist- 
ance in computing the perturbations, which were 
redetermined from 1819 to 1891, and afterwards 
to IgII. 
Backlund found clear evidence that sudden 
changes in the amount of acceleration took place in 
the years 1858, 1868, and 1895. He later found 
evidence of a fourth change about 1905; after this 
the acceleration had only one quarter of its value 
before 1858. He also studied the changes in 
brightness of the comet (it is generally brighter 
before than after perihelion), and made the tenta- 
tive suggestion that its particles are flat and 
oriented parallel to a particular plane, so that 
when seen edgewise they reflect little light. 
A valuable by-product was the determination of 
the mass of Mercury, the value being 1/9,700,000 
of the sun. This mass cannot be found except by 
comets, for even Venus is not appreciably per- 
“turbed by Mercury. Several approaches of the 
comet to Mercury yielded accordant results. 
Dr. Backlund showed great energy in adminis- 
tration; he found that. the climate of Pulkova was 
unsuited for delicate astrophysical researches, and 
succeeded in establishing branch observatories at 
NO. 2454, VOL. 98] 
NATURE 
[NovEMBER 9, 1916 
Odessa, and Feodosia, in the Crimea. He took 
part in the Russo-Swedish determination of an 
arc of the meridian, visiting Spitsbergen for this 
purpose. A valuable new method of determining 
the flexure of transit-circles was introduced at 
Pulkova under his auspices. In conjunction with 
Dr. Hough he formed a list of stars to be used 
as fundamentals in astrographical reductions, and 
arranged that the “Star Corrections” for 
several hundreds of them should be printed at 
Pulkova. 
The British observers who visited Russia for 
the eclipse of August, 1914, remember with grati- 
tude his kind help in the difficulties which arose 
from the outbreak of war. 
NOTES. 
WE notice with much regret the announcement, in 
the Times of November 6, that Prof. H. H. W. Pear- 
son, Harry Bolus professor of botany, South African 
College, Cape Town, died on November 3, at Mount 
Royal Hospital, Wynberg, at forty-six years of age. 
THE many friends of Major T. Edgeworth David, 
professor of geology in the University of Sydney, will 
be delighted to learn that he has recovered from the 
effects of serious injuries received while conducting 
mining operations in northern France, and hopes 
shortly to rejoin his regiment. / 
In answer to a question by Mr. Montague Barlow 
in the House of Commons on October 26, suggesting 
the adoption of the metric system of weights and 
measures, the Prime Minister stated that he was 
aware that the proposal to adopt the metric system 
had a certain measure of support, but that it was 
difficult to say how far this was general. He under- 
stood that the attention of Lord Balfour of Bur- 
leigh’s committee had already been directed to the 
subject. This reply will probably not be regarded as 
encouraging by those who are of opinion that the 
immediate obligatory adoption of the metric system is 
urgently necessary in order that we may be fully 
prepared, when the war is over, to cope with com- 
petition in foreign trade. Though the metric system 
has been legal for all purposes of internal and export 
trade for nearly twenty years, very little advantage 
has so far been taken of it by the trading community 
generally; while the large body of retailers are still 
completely ignorant of the nomenclaturé and equiva- 
lents of the system. 
Emeritus PrRorEssoR JOHN FERGUSON, who last year 
resigned the Regius chair of chemistry in the University 
of Glasgow, died, after a very brief illness, on Novem- 
ber 3. Prof. Ferguson was in his eightieth year, and 
had held the chair since 1874. His connection with 
the University had been continuous, as student, assist- 
ant, and member of the Senate, for well over sixty 
years. Among his pupils or assistants were Prof. 
J. M. Thomson, Sir William Ramsay, Sir J. J. Dobbie, 
Prof. G. Henderson, Prof. W. Lang, Prof. Carrick 
‘Anderson, Prof. M. A Parker, Dr. A. W. Stewart, 
and other distinguished chemists. He had made many 
contributions to the history of chemistry, to biblio- 
graphy, and to archeology, the most notable being his 
“Bibliotheca Chemica,’ published in two quarto 
volumes in 1906. He was an LL.D. of St. Andrews, 
and an honorary member of many British and foreign 
learned societies, including the Imperial Military Aca- 
demy of Medicine, Petrograd, and the Société Fran- 
caise d’Archéologie. Last year, on his retirement from 
the chair, he was appointed honorary curator of the 
