590 
NATORE 
[| Aprit 19, 1883 
Buchner (Munich), on the tribe of Bantu negroes distributed 
through the whole of South-west Africa. Prof. Giinther 
(Ansbach), on the latest investigations regarding the exact 
shape of the earth. Lieut. Wissmann, on his journey across 
Africa with Dr, Pogge. The oldest among the German African 
travellers now living, Dr. Riippel, had come to Frankfort to 
greet Wissmann upon his return, The fourth Geographentag 
will be held at Munich. 
FRoM a paper by M, Smicroff on the climate of the Caucasus 
{published in the Caucasian Zzvestia, and based on the researches 
of Dr. Wild on the temperatures in Russia), it is evident that 
although enjoying a warm climate, still the climate of the 
Caucasus, especially in the north, is quite continental. Thus, 
the average mean temperatures of the year are 5°"4 Cels. at 
Alexandropol, 8°*5 at Stavropol, 12°°6 at Tiflis, and 14°"3 to 14°°5 
at Bakou, Lenkoran, Kutais, Poti, and Redut-kaleh; but the 
yearly range of the average diurnal temperatures is still (with 
the exception of the two last places) as much as 20 to 30 degrees, 
while in Central and Southern Russia it varies from 22 to 35 
degrees. The highest temperatures observed on the Caucasus 
vary from 38°'5 at Tiflis, to 34°°4 at Poti; and the lowest from 
—25°°6 at Stavropol, to —17°°3 at Tiflis, and —6°°6 at Redut- 
kaleh. It is interesting to compare these temperatures with the 
+38°°8 and —62° observed at Yakutsk, and —63°'2 at Verk- 
hoyansk. Altogether, it isonly in Southern Transcaucasia that 
localities are found where the temperature does not fall below 
— 10°, and the southern limit of the region beyond which ten- 
peratures lower than —20° are no longer found, runs from the 
Crimea to the Caucasus range, and along the northern slope of 
this last, towards Khiva, Tashkend, and Peking. The whole 
range of temperatures observed at Caucasian stations is 60°"4 at 
Stavropol, 55°°8 at Tiflis, 45°°9 at Bakou, 42°"1 at Poti, and 41°°6 
at Redut kaleh. Of course it is nothing in comparison with the 
range at Yakutsk, where the inhabitants must be accustomei to 
experience differences of temperature ranginy a little more than 
100° (from —62° to +38°°8). But still it is large enough, espe- 
cially for the places situated on the plateaux. High-level 
meteorological stations are established at Goudaur (2156 metres 
above the sea-level) and Kvi am (2362 metres). Their average 
yearly temperatures respectively are 4°"1 (—8° in February and 
14°°3 in August) and 1°r (—14° in January and 123 in 
August). 
THE last number of the /evestéa of the Russian Geographical 
Society contains an elaborate paper, by M. Malakhoff, on the 
anthropology of the Vyatka region ; a description of iascriptions 
on rocks on the Yenisei, with drawings, by M. Schukin; a 
note on old Russian geography, by M. Arsenieff; an account 
on M. Balkashin’s researches into the K:rghiz, being a most 
valuable addition to our very imperfect knowledge of them. 
The author comes to the conclusion that the Kirghiz are not a 
separate nation, but a federation of several nomad tribes who 
inhabited Southern Russia, the Go i, the neighbourhoods of 
Dalay-nor, the sources of the Black Irtish, and the shores of 
the Baikal, who were mingled together by Genghiz Khan and 
his successors. M. Grigorieff contributes a note in which he 
shows that Henriette Island, which was discovered by the 
Feannette, is only the land which was sighted by Hedenstrom 
and Sannikoff from New Siberia in 1810, and that Bennett 
Island was seen by Sannikoff from the northern coast of New 
Siberia in 1811. There can be no doubt also that the land dis- 
covered by Sannikoff to the north-west of the northern extremity 
of the Kotelnyi Island exists in reality, but is more distant than 
Sannikoff supposed. This land, which was shown in dotted 
lines on older maps, but disappeared since Wrangell and 
Anjou’s journeys, ought to be reintruduced on our maps. The 
same number contains a note on the map of Bokhara of the 
Greek Vatalsi, a necrological notice of M. Techoupin, several! 
notes, and a new edition of the complete bibliography of the 
Amoor, by M. Bousse. One of the notes contained new astro- 
nomical determinations and hyp-ometrical measurements on the 
Yu-tschou, by Dr, Fritsche ; the Siio-Utai-shan proved to be 
only 9500 feet high, instead of the 11,452 feet given by 
Mellendorf. 
ACCORDING to intelligence from Tashkend, dated March 31, 
received by the Cronstadt Courier, it is in contemplation to send 
two Kus-ian Exploring Expeditions into Central Asia during 
the coming summer. The ostensible object of one is to survey 
part of the Pamir Steppe and fix certain points astronomically, 
with the object of connecting the Russian surveys with the 
English. The purpose of the other is to determine the astrono- 
mical position of places on the Oxus from the points of passage 
in its upper course down as far as Khiva, in fact the whole 
course of the river. 
From M. De Lesseps’s examination of the ground through 
which it is proposed to let the waters of the Mediterranean into 
the Tunisian and Algerian Chotts, he concludes that the scheme 
is perfectly practicable, and that there will be no difficulty as 
to boring and excavating. The size of the proposed inland sea 
will be fourteen times that of the Lake of Geneva. 
THE SOARING OF BIRDS» 
HE circling, soaring flight of birds on stiff, outspread wings 
appears to me a much more complex problem, and less 
easy of explanation, than thit of motionless hovering (poising). 
At the same time it has certain definite and characteristic fea- 
tures, which must depend upon and connote certain definite 
aérial conditions, and which should therefore afford us so many 
hints toward the solution. The whole phenomenon has been 
very clearly described in NATuRE (vol. xxiii. p, 10) by Mr. S. 
E. Peal, who appears to have had grand opportunities of ob- 
serving it at Supakati in Assam. [The explanation which he 
gives is, however, insufficient, because he does not show how 
the bird in falling with the wind can acquire greater ‘‘ impetus ” 
relative to the airy than it would if the air were still, But such 
greater “impetus” is necessary if the bird is to rise to a greater 
heigat than it would reach in still air.] 
The most typical instance that I have observed was on 
January 8, 1882, near King’s Lynn, in Norfolk. The whole 
country for many miles round is flat, broken only by trees, 
buildings, and sea walls or river embankment:, The wind was 
strong from the south. The birds (large gulls) were drifting 
away northwards towards the Wash, circling as they drifted on 
stiff, outspread wings at a height of 200 or 300 feet, and appar- 
ently rising higher. The level nature of the land forbade the 
notion that the wind had received an upward throw from any 
fixed obstacle in its path (though I shall show below that there 
may be upward currents in the air without the presence of a 
fixed obstacle). 
The circling appears to begin about 100 or 200 feet above the 
ground. A strong wind isa constant and (presumably) necessary 
condition. The bird descends with the wind, and then circles 
round to right or left, and rises against the wind to a greater height 
than it had before. Now if the whole mass of air were moving to- 
gether horizontally with the same velocity throughout, this action 
would be wholly inexplicable, for the bird would feel no more 
wind in one direction than in another, and indeed would have 
no evidence of the existence of any wind at all except in glancing 
at objects on the earth. The fact that the earth is slipping away 
under the air in a certain direction does not affect the bird’s 
relation to the air, and gives no reason why the bird should fall 
or rise at one phase of its circle more than at another. Still less 
does it furni h an explanation of the bird’s progressive ascent. 
We may therefore infer as highly probable that the air in which 
the birds are circling does not move in a mass, but that there is 
some differential movement in it which makes a great difference 
to the bird, whether it rises or falls with or against the wind. 
I think there are at least two types of differential movement 
in the upper air which admit of demonstration, and which should 
be tested in turn to see if either of them can give the meaning 
of the phenomenon of circling. 
(1.) First, there is almost always a greater velocity in the higher 
strata of the air than in the lower. The lower strata are 
delayed by friction on the earth’s surface, and the higher strata 
outrun them ; just as the water of a brook is delayed by friction 
against its bank, but flows faster in mid-stream. 
(2.) Secondly, where currents override or run past one another 
there is generally some vol/ing between them. This may be 
seen near the edge of any stream of water if the surface is 
smooth enough to exhibit the little swirls and whirlpools that 
are formed between the swifter and slower currents. In the air 
it may be seen on a grand scale on almost any windy day when 
there are separate floating clouds in the sky. Looking at right 
angles to the direction of the wind, each cloud is seen to have a 
Lord Rayleigh’s valuable letter on this subject (NaTUME, vol. xxvii. p. 
534) gives me confidence in offering the following considerations, which I 
had prepared last February, and have submitted to two or three mathe- 
matical friends. I congratulate myself on finding my own views in such 
close agreement with Lord Rayleigh’s.—H. A. 
