Marcu 4, 1897] 
NATURE 
421 
Tur additions to the Zoological Society's Gardens during the 
past week include a Bonnet Monkey (Macacus sinicus, 9 ) from 
India, presented by Mr. B. Dade ; a Black-handed Spider Monkey 
(Ateles geoffroyt) from Central America, presented by Miss 
Radley ; six Black-eared Marmosets (Hafale penictllata) from 
South-east Brazil, presented by Mr. John Russell ; an Egyptian 
Jerboa (Dipus agyptius) from Egypt, presented by the Hon. 
Mrs. Brett ; two Blood-breasted Pigeons (Phlogenas luzonica) 
from the Philippine Islands, two Barred Doves (Geofelza 
striata) from India, presented by Lady Edmonstone; an Up- 
land Goose (Chioephaga magellanica), bred in England, pre- 
sented by Mr. H. Birkbeck ; a Black Wallaby (A/acropus wala- 
batus, 8) from New South Wales, presented by Mr. G. J. 
Manders ; a Rough-scaled Lizard (Zonwrus cordylus), two Cape 
Bucephalus (Dzspholidus typus), a Hoary Snake (Pseudaspi's 
cana), a Ring-hals Snake (Sefedon hemachates) from South 
Africa, presented by Mr. J. E. Matcham: two Lataste’s Frogs 
(Rana datastit) from Turin, presented by Count M. Peracci ; 
two Himalayan Bears (Ursus ¢zbetanus, jv.) from Eastern Asia, 
three Royal Pythons (Python regius) from West Africa, de- 
posited ; a Great-billed Rhea (Rhea macrorhyncha) from North- 
east Brazil, a Bauer’s Broadtail (Platycercus zonarzius), two 
Graceful Ground Doves (Geofelia cuneata), a Shielded Death 
Adder (Wotech#s scutatus) from Australia, two Dunlins (772ga | ) 
| Since that date M. Perrotin, Dr. Terby, M. Cerulli, and others 
alpina), a Golden Plover (Charadrius pluviéalis), British, pur- 
chased ; a Hybrid Pheasant Antelope, ? (bred between 7rage- 
laphus gratus,§, and Tragelaphus spekzz,?), born in the 
Gardens. 
OUR ASTRONOMICAL COLUMN. 
THE ORBIT OF JUPITER’S FIFTH SATELLITE.—In the cur- 
rent number of the Astronomischen Nachrichten (No. 3403-4) 
Dr. Fritz Cohn gives a condensed account of an investigation he 
has undertaken with regard to the determination of the elements 
of the orbit of the fifth satellite of Jupiter. The observations 
used were those made by Barnard, with the 36-inch Lick re- 
fractor, from September 9, 1892; and by Herrn H. Struve, 
with the 30-inch refractor of the Pulkowa Observatory, from 
October 21, 1893. Fortunately for this investigation, the 
observations of Struve were very numerous at the opposition of 
1894, when extraordinarily bad weather hindered Barnard from 
making many measures. Limiting ourselves to a simple 
statement of the results obtained by Dr. Cohn, we may say 
that the orbit of the fifth satellite les nearly in the plane of 
Jupiter’s equator, and is very nearly circular in form. Assuming 
a circular orbit, and finding the differences, observed minus cal- 
culated, he was led to the following values for the improve- 
ment of the elements, leaving out of account perturbations 
that arise from the sun and the other satellites, but which, in 
consequence of the smallness of the distance of the fifth satellite 
from the primary, are practically insignificant. 
1893. October 309. Greenwich M.T. 
a 4 é 
wu, = + 0107 + 0078 
dA) = —- 0124 + 07'036 
é@ = 0700592. + 000080 
e233, 32 + O55) 
The elements, as deduced from the first two years’ improved 
values, were as follows :— 
1892. November 1. Creenwich M.T. 
uw = 22640 uw - U=344°°46 m=722°'63160 
é€ = 000501 
iP = Foy ey eae) tht, 
The daily motion, 7, corresponds to a period of revolution 
1th. 57m. 22°6790s. + O'0145s. 
This daily motion thus requires only the small correction of 
— 0°'00140 to produce, according to Marth’s ephemeris, the 
difference in the period of revolution of + 008s. 
THE ELLIPTICITY OF THE Disc or Mars.—In determining 
the ellipticity of a planet’s disc by the more common methods, 
the error due to the position of the line joining the observer’s 
eyes is liable to make an appreciable variation in the value 
deduced. 
NO. 1427, VOL. 55 | 
| is of more than unusual interest. 
By the use of a small prism in front of the eyepiece this error 
can be entirely eliminated, as in the case, say, of a double star, 
the line joining the two components, or in the case of a planet 
its diameter (equatorial or vertical) can be placed in any direction 
with regard to the vertical. 
Using the Repsold heliometer, Prof. W. Schur has taken 
advantage of both this method and the favourable recent oppo- 
sition of Mars to investigate the question of the form of this 
planet’s disc. 
The mean values for the oblateness (a —4/a) of the disc, where 
2a and 26 are the equatorial and polar diameters respectively, as 
obtained from a series of observations made on December Ze LY. 
16, 17, were as follows :— 
1896 it 2b a=a— dla 
Dec. 2 6°265 6'125 1 :44°7 
II 67310 6°135 1: 36°1 
16 6°210 6°12 1: 54°0 
17 6°240 6°12 1:54°3 
Taking the mean of these values, Prof. Schur finds for the 
oblateness of the disc a value of 1/47, the observations being 
freed as far as possible from all sources of observational error. 
Tue RoraTiIon OF VENUs.—Notwithstanding the persist- 
ence with which the planet Venus has been telescopically 
observed, the question of its period of rotation is still open. 
Schroter advocated a period of 23h. 21m., which was generally 
accepted until Schiaparelli, in 1890, stated that the time of 
rotation corresponded to that of revolution, namely, 225 days. 
have tended to strengthen Schiaparelli’s work by endorsing his 
observations. On the other hand, Schroéter was not alone ; for 
M. Niesten, M. Trouvelot, and Mr. Brenner, have all deduced 
from their own observations that the period must bea short one, 
namely, about 24 hours. The question, therefore, being, so to 
speak, in the balance, Mr. Percival Lowell’s communication to the 
current number of the Astronomschen Nachrichten, No. 3406. 
This observer has done so 
much for us in the case of the surface-markings of the planet 
Mars, that it seemed most probable that, turning his attention 
to Venus, we might have some definite results. Commencing 
observation on August 24, 1896, with the 24-inch refractor of 
his observatory, he found that the surface-markings were sur- 
prisingly distinct, but resembled lines rather than spots. ‘‘A 
large number of them, but by no means all, radiate like spokes 
from a certain centre.” These lines look purely natural, and 
have not the artificial appearance of the Martian Canals. 
From a great number of drawings made, a comparison showed 
that the rotation is such ‘‘as to keep the markings always in 
the same position with regard to the terminator.” Thus Mr. 
Lowell’s observations indicate that the rotation and orbital 
period of rotation must coincide, so that Schiaparelli’s observ- 
ations are again endorsed. 
Other physical characteristics of the planet’s surface, as ob- 
served at the Lowell Observatory, are as follows. 
No clouds appear to temporarily obscure the surface details. 
The intense lustre of the disc is shared by all the markings, as if 
‘<q bright veil of some sort were drawn over the whole disc.” 
This veil can be hardly anything but atmosphere ; for measure- 
ments, as in the case of Mars, have given indications of twilight, 
and therefore of the presence of an atmosphere. 
Further, Mr. Lowell states that there seems to be no 
evidence of polar caps. This observation does not well 
accord with those made by M. Trouvelot in 1877 and 
1878. It will be remembered that this observer not only 
found very distinct markings which he termed the polar 
caps, but was able to describe some important details of a 
varying nature. Ina former number of this journal (vol. xlvi. 
p. 468) it is stated that two of the most interesting features 
visible on the surface of Venus were the snow-caps at the 
extremities of the poles. These spots surpassed in brilliancy 
and importance all that M. Trouvelot had ever observed. 
Lastly, Mr. Lowell has found that some markings _be- 
come less distinct on nearing the central meridian. These 
changes vary considerably, and are found not to be a 
matter of obscuration. Since the positions of the markings 
had not moved relatively to the sun, the change could not have 
been intrinsic. Mr. Lowell suggests differences in the character 
of the rock or soil. The impression gained, on the whole, by 
Mr. Lowell, is that in the markings of Venus ‘‘ we are looking 
down on a bare desert-like surface.’ 
