February 15, 19 12] 



NATURE 



5^9 



The last two chapters are on the causes of the 

 struggle and nature's laws; they are somewhat dis- 

 cursive, and are not very helpful towards a better 

 understanding of the subject. 



The illustrations are from photographs and are well 

 done ; one of a fisherman is reproduced here. 



ATMOSPHERIC CIRCULATION OVER THE 



TROPICAL ATLANTIC 

 T^HE general circulation of the atmojphere proviaes 



A meteorology with one of its most fascinating 

 problems, because the details must ultimately be known 

 by observation, while the theoretical results 

 hitherto obtained cannot, with reasonable values for 

 friction, be made to agree quantitatively with the 

 observed motions. In the region of the trade- winds, 

 the average conditions persist with sufficient regularity 

 to make them the necessary basis of any wind-chart 

 and a fundamental criterion as to the general truth 

 of the conclusions deduced hydrodynamically on the 

 assumption of a known distribution of temperature. 

 It was for a long time confidently believed that above 

 the trade-winds themselves, at no very great heights, 

 there prevailed a counter-current, as steady and regu- 

 lar in its main features as the wind beneath it. Every 

 schematic representation of the circulation by Maury, 

 Ferrel, James Thomson, though differing in other 

 features, agreed in this one, and the conclusions 

 drawn by Hildebrandsson from the observations of 

 clouds supported them. 



It was therefore a surprise when Prof. Hergesell 

 reported in 1904 that observations made over the 

 Atlantic on the Prince of Monaco's yacht. Princess 

 Alice, had revealed the existence of an apparently per- 

 sistent and extensive N.W. wind above the N.E. trades. 

 The conclusion was based on observations made dur- 

 ing the course of one summer only, but the different 

 observations were sufificiently concordant to give 

 Hergesell confidence in the conclusion. Clearly such 

 a N.W. wind could not prevail around the whole 

 tropical belt because the flow of air southward in the 

 trades must be balanced by a corresponding flow north- 

 wards. It is, moreover, impossible to devise a scheme 

 of pressure distribution which would satisfy the 

 elementary principles of atmospheric motion, and per- 

 mit of N.W. winds at all points on a parallel of lati- 

 tude. The view was therefore received with some 

 scepticism, and in order to obtain fyirther, and, if 

 possible, conclusive evidence on the point, M. L. 

 Teisserenc de Bort and Prof. Rotch organised a more 

 systematic investigation of the conditions over the 

 Atlantic, and the results of the observations made on 

 voyages in 1905, 1906, 1907, are published in the 

 present volume. In 1905, 1907 the observations were 

 made solely in the N.E. trades in the summer months, 

 July, August, and in 1907 in September also. In 

 1906 two separate expeditions were made, the first in 

 February in the N.E. trades, the second from May 

 to the middle of August, in the region between the 

 Azores, 38° N., and Ascension, 8° S. The actual 

 observations were made by Prof. H. H. Clayton and 

 M. H. Maurice and other assistants. 



The first quarter of the book is devoted to descrip- 

 tion and discussion. In an introductory chapter of 

 fourteen pages, the authors refer briefly to the reasons 

 which induced them to undertake the work, sum- 

 marise the results obtained, and add some notes on 

 the boat, the Otaria, a " fish carrier," and on the 

 methods employed. They express their thanks to the 



' " Tr.-ivaiix Scientifiqties de rObserv.iioirn dc M^t^orologie Dynaiiiiqiie 

 (le Trappes, avec la collaboration de I'Observatoire de Blue Hill, ' " 1 ra- 

 vanx de I'Atmosphcre Marin« par Sondages Arfriens Atlantique Moyen et 

 Region Intertropicale." By MM. I,. Teisserenc de Bort et A. L. Kotch. 

 Pp. 243 + xvii plates. (Paris : Claiitliier Vlllars, igog.) 



NO. 2207, VOL. 88] 



Admiralty, who, at the request of Dr. Shaw, readily 

 undertook to supply coal to the Otaria at Ascension, 

 where there are no private supplies, but it is rather 

 humiliating to reflect that this represents the total 

 contribution of England to these recent investigations 

 over the Atlantic. 



M. H. Maurice, assistant at the Trappes Observa- 

 tory, who accompanied the expedition, contributes a 

 long article of thirty-six pages, giving the history of 

 the investigations and details of the methods used. 

 The article is illustrated by many photographs taken 

 on the voyages. Some of these are useful in helping 

 the reader to understand the procedure adopted for 

 making ascents, and others, such as the photographs 

 of clouds, form a contribution to meteorological art, 

 but it is difficult to see the special meteorological 

 significance of a photograph of a " Group of Women 

 and Children " at the Cape Verde Islands. 



A short notice of seven pages by Prof. H. H. Clay- 

 ton deals with the meteorological conditions in the 

 region of the trade-winds up to heights of 2000 

 metres. It is based upon results obtained during the 

 voyages of 1905, 1906, and is accompanied by a series 

 of diagrams showing the distribution of humidity 

 and temperature at different heights and latitudes. 

 One of the most interesting features is the relatively 

 warm and dry body of air at an altitude of about 1000 

 metres, which was found in every month between 

 latitudes 15° and 30° N. The paper is an example 

 of concise discussion, and it is to be regretted that it 

 does not embrace the whole of the observations for 

 all heights reached. 



The remaining three-fourths of the book contain the 

 results of the individual ascents, together with plates 

 illustrating the routes followed in the different expedi- 

 tions, and showing the character of the observed 

 motion at different places for heights up to 20 kilo- 

 metres. These results are proving of the grr.Ttost 

 value, not only for dealing with the problems which 

 the authors set out to solve, but in connection with 

 such questions as the motion In the stratosphere in 

 the equatorial regions and the gradient of pressure 

 at high levels. 



The general conclusion drawn from the observations 

 is that the N.E. trade-winds form .1 \:\\<y \\w m. in 

 height of which is only 1000 metres; .i1h.\. • ■ iius 

 a region where the wind has still a n< "m- 



ponent, and usually blows from N.W. < -.W. 



winds are, however, not found further south than lat. 

 20° in summer, which is about 12° north of the region 

 between the two systems of trade-winds. Above the 

 'egion of N.W. winds, anti-trades prevail, beginning 

 at a height of about 3000 metres near the Canaries, 

 lat. 30° N., and at 1800 metres, near Cape Verde 

 Islands, lat. 15° N. Thcv blow from S.E. near the 

 equator, changing gradunllv thmui^h S. to S.W., mar 

 the northern limit of \\\f tr.uir-w !•>■'- •"■' '--Hv 

 passing over into westerlv winds in ■ 

 Azores. The N.W. wind- .m-,,\, 

 appear to be a prolor 

 wind region of a mnont ft 



to that indiralid ' Mimson, and atlrihulrd 



by him to '1 '■ mentum hroiicrht from 



equatorial rv. 

 tropical clrnii 

 In agreement wit I 

 meteorologists b< ; 

 means of kit<s: .-iik^ ■ 

 It is o\-tronvl\ i^ratifv 



enablfd hv fhis prnlo '"h^ to 

 reach drfinit.' .-oik In ii'>tliing 

 but plausil^I"^ hvp' ' 

 that tho invi'stiL;.: 

 united effort will ■'< > =■' 



V It a r 



'lie inter- 

 features 

 iority of 

 ii-ins bv 



