16 
NATURE 
[ NOVEMBER 5. 1903 
this motion is that the three double bonds travel round the 
ring, whilst a labile form of the molecule with six free 
valencies is also indicated. In this way many of the 
peculiar properties of aromatic compounds may be accounted 
for. 
Tue additions to the Zoological Society’s Gardens during 
the past week include a Sooty Mangabey (Cercocebus fuls- 
ginosus) from West Africa, presented by Mr. C. J. Spencer ; 
a Levaillant’s Cynictis (Cynictis pentcillata) from South 
Africa, presented by Miss Bald; a Blue and Yellow Macaw 
(Ara chloropiera), a Red and Yellow Macaw (Ara ararauna) 
from South America, presented by General Sir Frederick 
Forestier Walker, K.C.B., G.C.M.G.: two Wharton’s 
Fruit Pigeons (Carpophaga wharioni), a Christmas Island 
Dove (Chalcophaps natalis), five Christmas Island Crabs 
(Birgus latro) from Christmas Island, presented by Captain 
A. W. Cole; a Chameleon (Chamaeleon vulgaris) from 
North Africa, presented by Mrs. T. Wallis: seven Spiny- 
tailed Mastigures (Uromastix acanthinurus) from North 
Africa, three Brazilian Amphisboenas (Amphisboena 
brasiliana) from Brazil, an Indian Eryx (Eryx johni) from 
India, two Sharp-nosed Snakes (Lioheterodon madagascar- 
sensis) from Madagascar, deposited; six Black Swans 
(Cygnus atratus) bred in the Gardens. 
= 
OUR ASTRONOMICAL COLUMN. 
Tue ForMation OF THE Potar Cars oN Mars.—An in- 
teresting paper, by Mr. Percival Lowell, which deals with 
the manner of formation of the Martian polar caps is pub- 
lished in No. 2 of the Lowell Observatory Builetins. Mr. 
Lowell observed the old polar cap on July 3, and found it 
to be diminishing; on July 5 it was only 29” of arc in 
diameter, equal to a diameter of 4°.1 on the planet’s sur- 
face ; and shortly afterwards he noticed that a new, large, 
white deposit had formed, north of Arethusa Lacus and 
touching the Pierius-Callirrhoe, in longitude 340°. This 
new white patch extended from the old polar cap to about 
latimde 55° N., and the Pierius, which it crossed, could 
be seen running through it, thereby showing that the 
appearance was due to a deposit and not to clouds, which 
would have obliterated all the features equally ; it also in- 
dicates that some Kind of vegetation, which had caused 
the deposit partially to melt, exists in the neighbourhood 
of the Pierius. 
From July 7 to 17 the dark line of demarcation which 
usually surrounds the cap became less marked, until it was 
finally obliterated by the encroaching deposit of frost, only 
@ superior whiteness, caused by the newly deposited frost 
lacking the sheen of the older, weathered and ice-welded 
snow, marking the presence of the older cap. It is only 
reasonable to suppose that this deposit actually was frost as 
we know it, for it is evident that a layer of frozen gas, such 
as solid carbon dioxide, would pass directly from the solid 
to the gaseous form under the pressure conditions obtain- 
ing = ro ae not exhibit the phenomenon of 
Slowly melting such as was obs i i 
patie esa bserved in the region about 
_ The quick melting of the outer and the durability of the 
inner portion of the Martian snow-cap are both explained 
by these observations, which show that the whole cap con- 
sists of a perpetual kernel which periodically becomes 
surrounded by a shallow transitory husk, the formation of 
which was observed by Mr. Loweil. ; 
The Same observer also performed some experiments in 
connection with the visibility of the Martian canals, which 
showed that a wire having an angular width of o”.69 at 
1800 yards could be readily “* glimpsed" with the naked 
eye, and from this he deduces that any canal having a 
width of half a mile on the planet’s surface should be readily 
observable with a good telescope. : 
Wotr’s VRIABLE Star 59, 1903, Crext.—A communication 
from Prof. Pickering to the Asironomische Nachrichien 
NO. VOL. 69] 
--- 
1775, 
(No. 3011) states that the star recently announced by Wolf 
as being a probable nova appears on a large number of 
plates taken at Harvard between October 29, 1891, and the 
present time. On a plate exposed on July 30, 1895, the 
spectrum of this star is of the fourth type, and, from the 
series of plates, it is seen that the brightmess varies by 
more than two magnitudes. 
In the same periodical Prof. Wirtz records an observ- 
ation made by him at Strassburg on October 15, when he 
found that the approximate magnitude of this object was 
10-5, and that a comparison of its focus with that of 
several known stars on the Strassburg refractor showed no 
difference. The identity of this variable with the star 
B.D. + 37°-3876 is confirmed by Prof. Wirtz. 
Prriopicat CHANGES IN THE COLOURS OF JUPITER’s BELTS. 
—In No. 3008 of the Astronomische Nachrichten, Mr. 
Stanley Williams directs attention to the periodical colour 
changes of Jupiter’s equatorial belts announced in vol. lix. 
(p. 378) of the Monthly Noiices. 
The computed times of the maximum and minimum 
brightness of the respective belts are very uncertain, and 
Mr. Williams suggests that careful observations should be 
immediately commenced with the object of exactly deter- 
mining the date when the red colour has entirely dis- 
appeared from the southern belt, and also the date of its 
corresponding reappearance, which will probably take place 
some time nest year. 
Mr. Williams's own observations indicate that the red 
colour has already almost entirely disappeared from this 
belt, some parts actually appearing blue, except in the 
neighbourhood immediately following the Great Red Spot, 
between longitudes 60 and 180, whilst the northern belt is 
of a bright, deep red colour. . 
Tue Muitipce Tam oF Comet i903 c.—In discussing a 
number of beautiful photographs of Borelly’s comet, which 
were obtained at Yerkes with a lantern lens having an 
aperture of 1-6 inches and a focal length of 6-3 inches, and 
are reproduced in the current number of the Astrophysical 
Journal, Prof. Barnard advances a novel explanation of the 
great changes of form which were observed in the tails of 
this and other comets. 
From two photographs taken at Yerkes on July 24, the 
one immediately after the other, and one taken by 
M. Quénisset at Nanterre on the same date, it is seen that 
an enormous change in the form of the tail took place at 
about 2h. 30m. (G.M.T.), when a section of it broke away 
from the head and travelled in a retrograde direction at 
a rate, referred to the motion of the head, of about 29 miles 
per second. As the velocity of the comet itself was, at this 
period, about 22 miles per second towards the sun, it will 
be seen that the actual velocity of the section showed a 
repulsion of 7 miles per second from that body. 
As an explanation of this phenomenon, Prof. Barnard 
suggests that either the outburst from the coma suddenly 
took place in a slightly different direction, or else the exist- 
ing tail was forcibly detached by some unknown body (e.z- 
a swarm of meteorites), and simply floated away in its old 
path, under the sun’s repulsion, until it was dissipated, or 
its light-emitting power died away; meanwhile, the new 
tail was formed by the material evolved by the coma, and 
for some reason the particles were evolved with a greater 
velocity than before, so that we get the phenomenon of 
the two tails nearly parallel for some distance, as shown 
on the Yerkes and other photographs. 
THE SWISS ASSOCIATION OF NATURAL 
SCIENCES. 
“THE cighty-sixth meeting of the Société helvétique des 
September 
Sciences naturelles was held at Locarno on 
Both as regards the number of visitors and the 
ae 
number and variety of the papers read, the gathering was 
highly successful. Several of the communications presented 
at the general meetings of the Association were especially 
well received. 3 
M. A. Pioda (Locarno), the president for the year, after 
referring to the naturalists of the nineteenth century in his 
presidential address, went on to show that, in the same way 
| as all other sciences have gradually been differentiated from 
a ee 
