182 
NATURE 
| Dec. 21, 1882 
THE Russian Geographical Society has addressed to other 
scientific societies of Russia a proposal to collaborate in the 
publication of a general description of Siberia. The Geogra- 
phical Society undertakes for its part the publication of a 
geographical description and of a general bibliographical index 
of all works and papers on Siberia. 
THE Belgian expedition for the investigation of the Upper 
Congo has left Antwerp on board the steamer Yarkaway. The 
party consists of Dr. van der Heuvel, Herr Schaumann, an 
Austrian officer, and several mechanics. The expedition takes 
out large stores of goods, including samples of the seeds of all 
nutritious vegetables grown in Belgium. They are to proceed as 
quickly as possible to the furthest of Stanley’s stations, and then 
penetrate further if possible. 
THE additions to the Zoological Society’s Gardens during the 
past week include a Chacma Baboon (Cynocephalus porcarius ? ) 
from South Africa, presented by Mr. J. W. Browne ; a Macaque 
Monkey (Macacus cynomolgus) from India, presented by Lady 
Sibyl Tollemache ; a Smooth-headed Capuchin (Cebus monachus) 
from South-East Brazil, presented by Mr. A. J. McEwen; a 
Squirrel Monkey (Chrysothrix sciurea & ) from Guiana, presented 
by Mr. M. Escaré ; 2 Rhesus Monkey (Macacus erythreus é) 
from India, presented by Mr. G. V. Sawyer; two Leadbeater’s 
Cockatoos (Cacatua leadbeatert) from Australia, presented by 
Mr. C. J. Harvey; a Common Barn Owl (Strix flammea), 
British, presented by the Rev. A. Reece ; a Ring-hals Snake 
(Sepedon hemachetes), a Rhomb-marked Snake (Psammophylax 
vhombeatus) from South Africa, presented by Mr. H. Pillans; a 
Lesser White-nosed Monkey (Cercopithecus petaurista 6) from 
West Africa, deposited ; a Long-eared Owl (Aszo otus), British, 
a Marbled Cat (Féis marmorata) from Assam, purchased ; 
a Red Kangaroo (Aacropus rufus 6) born in the Gardens. 
OUR ASTRONOMICAL COLUMN 
MEASURES OF DouUBLE STARS.—We receive at about the 
same time several important series of measures of double stars. 
(1) ‘* Results of double star measures made at the Sydney 
Observatory, N.S.W., 1871 to 1881,” under the direction of 
Mr. H. C. Russell, Government Astronomer for New South 
Wales. From 1871 to 1874 the instrument employed was a very 
fine 7}-inch refractor by Merz ; after 1874 the 114-inch refractor 
by Schréder was substituted, the same method of observation 
being followed with both instruments. For the more difficult 
objects, a pewer of 330 was applied on the Merz telescope, 
and one of 800 on the larger refractor. The objects mea- 
sured include about 746 of Herschel’s stars, and it is unneces- 
sary to say more than this, to show the importance and value 
attaching to the catalogue, no measures of a large number of 
the stars having been put upon record since the publication of 
Sir John Herschel’s Cape Volume. In addition to these objects, 
however, Mr. Russell’s catalogue includes measures of 350 new 
double stars detected at Sydney, and he remarks that it would 
have been easy to double the number if he had adopted the 
same limit of distance as Sir John Herschel, and without making 
any very strict examination of the southern heavens, which will 
be a hint to future workers in this branch of astronomy in the 
other hemisphere. Some of Jierschel’s stars, Mr. Russell says, pre- 
sent considerable difficulty, but are probably in motion ; thus + 
Lupi, an easy double star in 1836, is now single under the 
highest power on his large equatorial ; + Lupi, which Herschel 
found ‘‘ excessively difficult,” is now quite an easy object with 
the Sydney refractor ; 4 4854 is another star of the same cha- 
racter; in June, 1872, it was easily divided with power 230 ; in 
June, 1874, it could not be divided with any power; and in 
July, 1880, it presented only a round disc with all powers on the 
large telescope. 
Mr. Russell has made an innovation in the manner of expres- 
sing the dates of the separate sets of measures, which appears 
an unfortunate one: instead of giving them according to the 
u ual method, as fractions of the different years, he has three 
columns with ‘‘ Day of the month,’’ ‘‘ Month of the year,” 
and ‘* Year in the 19th century,” and this inconvenient expres- 
sion of dates is not remedied without some trouble, by means of 
the table at p. 68, showing day and fraction of year. The 
computer of double-star orbits in taking means of sets of mea- 
sures for an epoch to work upon, will hardly appreciate this 
innovation. 
(2) ‘* Micrometric measurements of double-stars ” in vol. xiii. 
part I, of ‘* Annals of the Astronomical Observatory of Har- 
vard College.” This is a valuable catalogue of measures of 
about 350 stars in upwards of one thousand sets, made with the 
15-inch refractor at Harvard College, chiefly in the years 1866- 
1872, under the direction of Prof. Winlock, but including a few 
obtained by the Bonds, and by Mr. Waldo, which have pre- 
viously appeared in the Proceedings of the American Academy 
of Arts and Sciences, and in the Astronomische Nachrichten. 
The catalogue includes nearly all the more interesting binaries 
and many difficult objects. In addition, Prof. Pickering pub- 
lishes a list of 179 double stars discovered at Harvard College 
Observatory, some of which have been independently detected 
by Mr. S. W. Burnham; these were found to a considerable 
extent during an exploration of the southern heavens, occasion- 
ally instituted in the intervals of other observations. In the 
cases of some of the principal revolving doubles as y Virginis. 
70 Ophiuchi, &c., the measures extend to the year 1876. 
(3) ‘‘ Measures of the principal double stars in rapid orbital 
motion,” made in the years 1875-1882, with the Merz refractor 
of the Observatory of Brera, Milan by Prof. Schiaparelli; an 
important series of results which will be most welcome to those 
who are engaged in the investigation of double star orbits, since 
in most cases, there are measures later than any others available 
at the present moment. We extract a few of the more recent 
mean results :— 
Position Distance 
° “ 
¢ Cancri (A: B) 1882°247 75°07 07980 
@ Leonis eee 1882°363 89°99 O55 
& Ursze Majoris 1882386 261°06 1°925 
nCoronz Borealis ... 1882°503 135°37 0.594 
4” Bootis 1882°521 120°40 0°795 
¢ Herculis 1882°602 IOI’55 1°473 
7 Ophiuchi 1882°600 252°13 1°860 
70 Ophiuchi 1882°609 51°83 2°336 
No trace of the companion of yy Coronz Borealis was visible 
in the years 1875-1881. In 1882 a prominence was once 
suspected at 120°, but at other times the star was single. In 
1875-1879, however, this star was single in the Washington 
26-inch refractor. 
PHYSICAL NOTES 
ProF. W. KOHLRAUSCH gives the following as the result 
of recent experiments on the electric conductivity of the haloid 
salts of silver. Chloride, bromide, and iodide of silver at tempe- 
ratures above their melting-points conduct far better than the 
best conducting liquids (sulphuric acid, &c.) at ordinary tempe- 
ratures do. Chloride of silver conducts best, iodide worst of 
the three. The chloride and the iodide of silver change their 
resistance very greatly and suddenly on solidifying, the resistance 
increasing more than a million-fold by cooling through 20°. 
More remarkable still, iodide of silver undergoes absolutely no 
change of conductivity at its melting-point (540°), but shows a 
rapid decrease at the temperature (145°) at which it passes from 
the amorphous to the crystalline state. 
NEw combinations to serve for direct-vision prisms have been 
suggested recently by several persons. Mr. C. D. Ahrens uses 
a bisulphide prism cemented between two flint glass prisms, 
giving a wide dispersion with little loss of light. Herr Fuchs 
employs a single isosceles glass prism in the position of minimum 
deviation, a silver-faced mirror being attached to the basal face 
of the prism to rectify the ray after emergence. Signor A. 
Riceo- has described a similar combination, a total-reflexion 
prism being substituted for the mirror. He has also constructed 
the second prism of the combination of a four-sided form, so 
that it not only rectifies the ray which has been deflected by the 
first prism, but also augments the dispersion of the first prism by 
a nearly equal amount. 
THE electric resistance of mercury is, according to R. Lenz, 
affected by pressure. Between the limits of 2 and 60 atmo- 
spheres’ pressure, the resistance of a quicksilver column 1°2 
metres long, inclosed in thermometer tubing, diminished *o2 per 
cent. for each additional atmosphere. 
