November 16, 1905] 



NA TURE 



55 



Thus Prof Hergesell believes that the north-west 

 wind which was found overlying- the thin north-east 

 stratum is a return current, or anti-trade, for he 

 savs : — " Der Luftersatz im Anti-passat erfolgte 

 deshalb vorwiegend in der von uns durchforschten 

 Gegend aus nordwestlichen Richtungen " (Aero- 

 nautical Conference, St. Petersburg, 1904, supple- 

 ment vii., p. 91). 



It appeared to the writers that these conclusions, 

 which tended to invalidate the existence of the upper 

 anti-trade, required further investigations, and by 

 mutual consent we decided to have these carried on 

 by two of our assistants, .Mr. Clayton, meteorologist 

 at Blue Hill, and M. Maurice, assistant at Trappes, 

 aboard the Otaria, a large fish-carrying steamer, 

 equipped with the electric kite-reel which M. 

 reisserenc de Bort had used for kite-flying at sea. 



A study of the high barometric pressures at the 

 Observatory of Trappes (see Comptes rendus, 1S99) 

 led to the conclusion that there exists, generally, at 

 a moderate altitude, a zone of light winds which 

 ordinarily the kites cannot penetrate. While it is 

 true that at sea an artificial breeze may be created 

 by steaming in a direction contrary to that of the 

 wind, this method is inefficient in the trades, because, 

 if, as is usually assumed, there is almost complete 

 reversal in the directions of the upper and lower 

 winds, the top kite arrives in the south-west current 

 while the others are still in the north-east wind, and 

 consequently the flight is stopped just where the 

 change of regime commences. Therefore it is 

 necessary to employ a single kite and a boat which 

 is sufficiently fast to lift the kite regardless of the 



no. 1 88 1, voi. 73] 



direction of the wind, but as these conditions cannot 

 always be realised, in order to attain great heights 

 on this expedition the paper pilot-balloons already 

 tried at Trappes were used. Since these balloons 

 were only intended to show the direction of the 

 wind, they did not usually carry instruments, and 

 their drift and height were determined by simul- 

 taneous angular measurements at the ends of a base- 

 line on thi' shore, with the exception of one balloon 

 which was observed from the boat. These soundings 

 of the atmosphere, executed at various places, notably 

 at Madeira, Teneriffe and Cape Verde Islands, and 

 also over the open sea, gave the following results, to 

 which are added observations of winds on two tropical 

 mountains and during one of the kite-flights. 



In the table on p. 56 the first column indicates the 

 upper limit of the north-east trade, and the second 

 column the limit of the associated north-west wind. 

 tltes. heights being expressed in metres. In the third 

 column the figures in parenthesis show the maximum 



Fig. 2.— Direction of 



1 by the tracks of 



heights at which the balloons were observed moving 

 in the anti-trade, from south-east, south, or south- 

 west. 



There follow observations at different heights on 

 the peaks of Teneriffe and Fogo, the figures after the 

 direction of the wind being its velocity in metres per 

 second. There is also noted the drift of the clouds 

 passing above the peaks. The diagrams (Fig. 2) re- 

 present the direction and speed of the balloons which 

 were sent up from Teneriffe on July 9 and from St. 

 Vincent on July 17. 



The tables and figures show that the winds blow- 

 ing inward the equator have a direction varying 

 between N.E. and N.W., these last being usually 

 above the N.E. stratum, the thickness of this layer 

 of the trades in the vicinity of Teneriffe being about 

 }ooo metres or 5000 metres. Above it blow S.E., S., 

 and S.W. currents which form the anti-trades, its 

 thickness being probably very great, though its 

 densitv is small. Thus, as was deduced from the 

 observations of clouds and volcanic dust, the east 

 wind in the vicinity of the thermal equator extends 

 very high. At the Cape Verde Islands the south-east 



