616 
NATURE 
cepted by the planet, the planet’s mean distance and its 
photometric magnitude at opposition Mr. Gore evolved a 
formula which gave the following values for the albedoes 
of the several planets :-—Mars, 0-2072; Jupiter, 0-595; 
Saturn, 0-6744; Uranus, 0-61; and Neptune, 0-627 
THE Second GtLopuLtaR: CLUSTER IN 
MESSIER g2.—No. 3, vol. viii., of the Astronomiska 
Takttagelser och Undersikningar a Stockholms Observ- 
atortum is devoted to a discussion, by Dr. Karl Bohlin, 
of the measures of a plate showing the cluster Messier 92, 
taken at Stockholm on April 29, 1898. The conditions 
of measurement and the corrections applied are discussed 
in full, the actual measures being tabulated. The number 
of stars considered is three hundred and forty-eight, and 
of each of these the position and magnitude for 1898-0 
are given. In a third table the resulting places are com- 
pared, for twenty-nine stars, with those obtained from 
measures made at Upsala in 1873, and the apparent 
proper motions deduced. A diagram given at the end of 
the volume shows these proper motions graphically, the 
Sreatest differences (Stockholm-Upsala) being Aa=+6"-6 
and AS’=—4".6, whilst the mean values are +1"-5 and 
—1".7 respectively. 
HERCULES, 
Hattey’s Comet.—Knowledge and Scientific News for 
March (No. 3, vol. iv., p. 57) contains an interesting 
article by Mr. F. W. Henkel on Halley’s comet. Mr. 
Henkel discusses cometary phenomena and mechanics’ in 
general, showing thcir application in the observed appear- 
ances of Halley’s famous object in particular. The 
apparitions are carried back as far as 1066, although the 
identity of the object represented on the Bayeux tapestry 
with that known as Halley’s comet cannot yet be re- 
garded as beyond doubt; probably the investigation now 
being carried out by Mr. Crommelin may settle this ques- 
tion. Many other interesting points, such as the per- 
turbative action of Jupiter, the existence of an inter- 
planetary resisting medium, and the various features 
presented by Halley’s comet at previous apparitions, are 
dealt with ‘in a very simple manner in Mr. Henkkel’s 
paper. 
EcLipsESs OF JuPITER’s SATELLITES, 1878—1903.—The 
results of the photometric observations of the eclipses of 
Jupiter’s satellites, carried out at the Harvard College 
Observatory between June 23, 1878, and the end of 1903, 
ave published by Prof. E. C. Pickering in part i., vol. 
lii., of the Annals of the Astronomical Observatory of 
Harvard College. The present publication contains simply 
the observational records in detail, with notes on the 
same, and a catalogue of the eclipses which were observed. 
The discussion of the entire material Dye bora emeAs 
Sampson, of Durham University, will appear in part ii. 
of the same volume. 
RAINFALL IN GERMAN 
AFRICA. 
[N spite of native risings and recalcitrant Parliaments, 
our German cousins manage to carry on meteorological 
observations in their African possessions, and some results 
of their work which are of great importance in connection 
with the general meteorology of South Africa have just 
been issued as a supplement to the official ‘‘ Deutsches 
Kolonialblatt.”’ In the first section of this publication Dr. 
Ottweiler has collected and re-printed all trustworthy 
rainfall records—both official and unofficial—from German 
South-West Africa, and, for the sake of completeness and 
comparison, he has added returns from a number of stations 
in the adjoining British and Portuguese territories. For 
this alone meteorologists will be grateful to him. A 
supplementary table giving the positions and heights of 
the stations, and in most cases a brief description of the 
ot! 1/A*-a] features of the country surrounding them, will 
alsy percentcome. 
As is wecbe expected in so ‘‘ young”? a country, the 
material coilected is far from homogeneous, and, more- 
SOUTH-WEST 
1 Wissenschaftliche Beihefte zum deutschen Kolcnialbl-tte, 20 Rand, 
1 Heft. Mitteilungen aus den deutschen Schutzgebieter ; Die Nied-r- 
schlags-verhaltnisse von Deutsch-Sudwestafrika. By Dr. F. yon Danckel- 
man. Pp. 84. (Berlin: S. Mittler und Schn, 1907.) 
NO. 1956, VOL 75] 
[APRIL 25, 1907 
over, most of the stations are of very recent date. The 
author thus had before him the task of ‘* weighting ’’ the 
means deduced from the observations to render them 
approximately comparable among themselves before pro- 
ceeding to discuss results. The process is not entirely 
satisfactory, but unless we are to refrain from drawing 
conclusions until a homogeneous body of statistics is avail- 
able, some manipulation of the figures is necessary. 
The results, which are illustrated in a number of 
admirable plates, are of exceptional interest, though they 
will be disappointing to those concerned with the economic 
development of the country. The coastal districts may be 
described as practically rainless, which is remarkable, as 
the prevailing winds are. southerly or south-westerly 
throughout the year, and the land rises tolerably rapidly. 
In most parts of the world, sea breezes blowing on to 
rising land yield a copious rainfall, but on the coast of 
German South-west Africa the air is derived from higher 
and colder latitudes, and, as it blows over the cold 
Benguela current before it reaches the land, it contains 
little moisture when it commences its forced ascent. The 
heating effect of the sun far outweighs the dynamical cool- 
ing due to the ascent, and the condensation stage is never 
reached. Practically the only moisture which reaches the 
land near the coast is derived from the heavy fogs, which 
in winter are of almost daily occurrence. The winter rain- 
fall, which is so prominent a feature in the west of Cape 
Colony, does not extend north of the Orange River. 
In the more eastern inland districts the dry south-west 
wind prevails throughout the winter, and this portion of 
the year is accordingly rainless. In summer the wind 
shifts to the eastward, and a limited amount of moisture 
manages to reach the country from the Indian Ocean. In 
the neighbourhood of Windhuk the average annual rain- 
fall is about 12 inches or 14 inches, and in the extreme 
north-east of the colony it exceeds 26 inches. 
When the details of this fall are examined its value for 
economic purposes is found to be but small. Great fluctu- 
ations occur in the annual totals, which are of all the more 
importance, as the amounts are so small. Thus in the 
country round Windhuk the fall during the last twenty 
years has fluctuated between 47 per cent. and 210 per cent. 
of the average. Further to the south, conditions are con- 
siderably more unfavourable. 
Great variability in the annual rainfall is not the only 
disadvantage from which the country suffers. Almost all 
the rain falls in thunderstorms, and torrential downpours 
are the rule rather than the exception. A single, though 
by no means isolated, instance will suffice to give an idea 
of the prevailing conditions. At Udabis in the year 1900 
the total rainfall was 9-5 inches, and of this amount 
6-5 inches fell in the course of three consecutive days, 
leaving only 3 inches to be distributed over the remaining 
360 odd days. 
It is interesting to compare the German results with 
those which have just been issued by the Governments of 
British East Africa and Uganda for the year 1905. In 
British East Africa the annual totals at thirty-three stations 
ranged from 16 inches to 99 inches. Only four stations 
experienced more than two absolutely rainless months, and 
in only two cases were these consecutive. A summary of 
totals for past years, which is appended to the report, 
shows considerable fluctuations in the amount. At three 
stations with records extending over at least eight years, 
the totals fluctuate from about 4o per cent. to about 150 per 
cent. of the mean value for this period. 
From Uganda, rainfall data are given for nine stations. 
The totals for these varied from 37 inches to 96 inches. 
Only one station had an absolutely dry month. At 
Entebbe the year was the wettest on record. The total 
fall was 65-74 inches, 112 per cent. of the average for the 
last six years. Ten years’ records (the first four incom- 
plete) now exist for this station. During this period no 
absolutely dry months were experienced. 
The British Empire has not yet produced a work on the 
meteorology of any of its possessions in tropical Africa 
which can be compared with that just issued in Germany, 
but it is gratifying to find that the Governments responsible 
for the administration of our share of the Dark Continent 
are realising the importance of meteorological observations, 
and of their systematic publication. 
