80 
the Malay Archipelago. This network of rainfall observa- 
tion now includes 150 stations scattered over the islands 
at heights varying from near sea-level up to 6404 feet. 
The averages of the three years show that the mean 
annual rainfall over the archipelago varies from about 
60 inches in Timor to upwards of 200 inches at some 
spots among the western slopes of Sumatra. But the de- 
termining character of the rainfall, as regards the climates 
is not the absolute amount that falls annually but rather 
the manner of its distribution through the months of the 
year. Over the larger proportion of the islands rain falls 
copiously every month of the year; but as regards some 
of the islands, the year is divided into dry and wet 
seasons as markedly as is seen in the climates of India. 
The reason of this difference is readily seen on exa- 
mining the distribution of atmospheric pressure during 
the months from Australia to China with the prevailing 
winds resulting therefrom. During the winter months 
pressure is high in China and low in the interior of 
Australia, the mean difference being nearly three-quarters 
of aninch. Between the two regions the fall is practi- 
cally uninterrupted, and the Malay Archipelago lying 
between them is swept by northerly winds. Since these 
winds have traversed no inconsiderable breadth of ocean, 
they deposit a copious rainfall particularly on the northern 
slopes of the higher islands, and consequently the rainfall 
of these months is large over all the islands without ex- 
ception, the mean monthly amount in some places exceed- 
ing 30 inches. It is to these same winds that the north 
of Australia owes its rainfall ; and it is their strength in 
any particular year which determines the distance to which 
the annual rains penetrate southwards into the interior 
of that continent. 
On the other hand, during the summer of the northern 
hemisphere, atmospheric pressure is high in the interior 
of Australia, and low in China, the mean difference being 
aboot half an inch, and between the two regions the fall 
in the mean pressure is continuous and uninterrupted, 
and consequently southerly winds prevail over the inter- 
vening region. These winds are dry and absolutely 
rainless over the north of Australia, and over Timor and 
the other Malay islands, which are separated from Aus- 
tralia but by a comparatively narrow belt of sea. During 
the three years no rain whatever fell at Timor during 
July and August, and the fall was small during June, Sep- 
tember, and October. As the winds pursue their course 
to northward, they eagerly lick up moisture from the sea, 
so that by the time they arrive at Amboyna they have be- 
come so saturated with moisture that the monthly rain- 
fall of that place rises at this time of the year to nearly 
30 inches. At some distance to the west of Timor rain 
falls at this season more or less regularly every year, the 
amount increasing in proportion to the extent of ocean 
traversed by the south-east winds, which blow towards 
the islands from the direction of Australia. These 
marked and vital differences of the climates of the Malay 
Archipelago, which, as they depend essentially on the 
geographical distribution of the land and sea of this 
part of the globe may be regarded as permanent, have 
played no inconspicuous part in the remarkable distri- 
bution of animal and vegetable life which characterises 
the archipelago. 
THE COMET 
{02 receipt of observations from Australia, made 
between September 8 and 16, has allowed of the 
determination of the orbit of the present comet exclu- 
sively from positions obtained before the perihelion 
passage when it made so close an approach to the sun. 
From a mean of the Melbourne and Windsor N.S.W. 
observations on September’ 9, and the Melbourne meri- 
dian observations on September 14 and 16, Mr. Hind 
has deduced the following orbit :— 
NATURE 
[Mov. 23, 1882 
Perihelion passage, Greenwich M.T., Sept. 17°21897 
tal, 
Longitude of perihelion 275 50 20 
Ascending node ... 345 53. 2 
Tnclinationt eee: 38 017 
Log. perihelion dist. ... 7°8501274 
Retrograde. i 
The longitudes are reckoned from the apparent equinox 
of September 17, and it should be mentioned that the 
small corrections have been neglected. On comparing 
the observed places with those calculated from the ele- 
ments founded upon observations before perihelion, the 
following differences remain :— 
Aa. cos 6 (¢ — 0) ab 
Tebbutt ... Sept. 8 - 25 - 3 
Tebbutt and 
Melbourne Dili Niche 82. fie 2 ) 
Melbne. merid. ry we + 21 +7 
” ” 15 AE a8 5 
“A op to) Sp BW soto sce ° 
Aq. Commone een iss ek) <b O02) Sc see 
When however we compare with the meridian obser- 
vations at Dunecht and Coimbra on September 18, or the 
day after the comet’s close approach to the sun, the com- 
puted place is found to differ by several minutes of 
arc from that observed, and at the time when Mr, Gill 
noted the comet’s ingress upon the sun’s disc, calculation 
places it 2’ 30” within his limb. These differences 
appear to point to sensible perturbation about the peri- 
helion passage, but a stricter discussion of observations 
before and after the time when the comet attained that 
position in its orbit, will be needed before any re- 
liable judgment on this important question can be 
formed. It may be noted also that a very small change 
in the time of perihelion passage has a comparatively 
large effect upon the geocentric positions about that 
epoch. 
Mr. W. F. Denning communicates the following esti- 
mates of the length of the tail of this comet made by 
him at Asbley-down, Bristol; the dates are astro- 
nomical :— 
Octo -2 210) /Oct.. 30" 122 22)|NoviSieeaes 
FL Ge INOVERNG) | ceases) 59 De ee 
Ap. ae eso HC Ape On, 22S 
To form an idea of the real extent of the tail, assume 
it first to be situate in the direction of the radius-vector, 
as is most frequently the case. At 6 a.m. on November 
7, by the orbit last published in NATURE, the distance of 
the comet's nucleus from the earth (expressed in parts of 
the earth’s mean distance from the sun) was 174844, and 
its distance from the sun was 1°4958, the earth’s radius- 
vector being o'9005. Hence we find the angle at the 
comet between lines supposed to be drawn to the earth 
and sun respectively was 38° 49’, from which it appears 
that an angular extent of 23° would give a real length, 
as a prolongation of the radius-vector of rather over 
196,000,000 miles. But this must be an outside estimate 
of the linear distance of the extremity of the tail from 
the nucleus, as there was sensible curvature of the tail, 
the effect of which may be readily seen by a graphical 
process upon the above data. 
We subjoin the Melbourne meridian-observations, to 
which reference has been made :— 
Melbourne M.T. Apparent R.A. Apparent N.P.D. 
h 
eet Ss Stee Se x: Sy i, 
Sept. 14...23 10 13°7 10 45 53°34 89 55 471 
Ti5.23) 22-3050 -.3) eT) 2 rAeSO 89 29 39°2 
16...23 39 0°73 Miz avons 88 47 55'2 
The observation of September 15 was made with great 
difficulty, the comet being obscured by cloud. 
