|amarv a, [gig 



NATURE 



349 



SCending air. Nov. we know that I he- opposite is 

 in reality the truth; the cyi core, 



the anticyclone a warm one. Another theory oi 

 equal simplicit) and perhaps oi even greatei 

 antiquit) explained the general circulation ol 

 winds around the globe. It was argued that 

 solar beating made the equator very much warmer 

 than the poles; therefore there must l>e a rising 

 current at the equator, a poleward How of air 

 in the upper layers of the atmosphere, a descend- 

 in- current in polar regions, and an equatorial 

 How iii the lower layers. To question the validity 

 of such a theory would have been regarded as 

 almost an impertinence. 



In a recent paper ' Hildebrandsson lias dealt 

 in a comprehensive manner with this question of 

 world circulation, avoiding preconceived theories, 

 but collecting all available information on the 

 subject. Incidentally he puts forward several 

 very cogenl reasons why the simple theory out- 

 lined above is untenable, though there can be 

 few meteorologists of the present day who regard 

 il at all seriously. The main surface currents 

 have for a long lime been fairly well known, and 

 it is with the upper winds of the troposphere that 

 the greater part of this paper is concerned. The 

 chiel sources of information arc (i) cloud observa- 

 tions from the international network of stations 

 which observe cloud motion, and (2) results ol 

 pilot-balloon and ballon-sonde ascents. The 

 former afford the larger body of data, while the 

 latter present more detailed information and pro- 

 vide valuable confirmation of the general con- 

 wise arrived at. 



The main general system of world currents 

 is made up as follows: (1) Over the thermal 

 equator there is a current from east to 

 west at all heights, weak near the surface of 

 the earth, but very strong- in the upper layers ol 

 the atmosphere. (2) In the temperate zones the 

 currents are from west to east. In the lower 

 layers of the atmosphere the intermediate reg 

 between these two current systems contain the 

 tropical anticyclones and the trades, which blow 

 from N.E. in the northern hemisphere, and from 

 S.E. in the southern. In the upper layers the 

 rly wind over the equator veers in the 

 northern hemisphere successively to S.K., S., and 

 S.W. as on northward, thus turning- into 



the well-known counter-trades. These feed the 

 upper part of the tropical anticyclone from the 

 equatorial side, while the polar side is similarly 

 fed by a deviation of the main westerly current 

 to WW. 



The above form the chief wind systems of equa- 

 torial and temperate latitudes. In arctic and 

 antarctii regions data are more scanty, and the 

 wind currents do not seem to fall into any such 

 simple system in these parts of the globe. It is 

 interesting to learn that the great monsnoii 

 currents, which have such an important infmeha 

 on the meteorology of man) regions of the earth, 

 are relatively shallow, being- not more than 4 km. 



1 '" R4saltals <J-s Recherche* Empiric/lies <ur les Mouvemems Gcncraiix 

 de PAl ReKiae Societatis Sciential I 



ser. 4. vol. v., No. 1. Pp. 50+plates. (Upsala, 1918.) 



1, VOL. I02] 



to 5 km. in depth. The) must be regarded only 

 as great perturbations in the general system of 



I alion outlined above. Similarly, the cyclones 

 and anticyclones of temperate regions are pheno- 

 mena of the lower layers, above which blow in 



ral the undisturbed westerlies at great 

 heights. 



A valuable feature oi the pap is the numerous 

 tables, which set out the dala obtained from 

 different parts ol the globe. Mention must also 

 be made of two charts showing the upper wind 

 currents which prevail above the North Atlantic 

 " High " in summer and winter. It is unfortU 



practically no velocities are given, wind direc- 

 tions only 1 d with. The reasons for this 

 arc fairly obvious in the case of cloud data, but it 

 would have added to the value of the discussion if in 

 the tabulated pilot-balloon observations wind velo- 

 city had been given as well as direction. Through- 

 out the paper directions are indicated by degrees 

 from one of the cardinal [joints, but no uniform 

 plan seems to be followed. There appears little- 

 justification for denoting a direction as X. 70 W. 

 in one place, and W. 20 N. in another, to quote 

 one example. It is desirable to point out that 

 the references on pp. 12-17 lo tne plates at the 

 end of the paper are mostly in error. These detail 

 imperfections do not, however, appreciably detract 

 from the great value of the paper as a compre- 

 hensive study of world air currents. 



J. S. D. 



THE VISIT OF PRESIDENT U'lLSON. 



THE visit of .Mr Wilson to Europe, and to 

 England especially, is an event of the 

 highest moment, not merely because it is the first 

 time that a President of the United States has left 

 the shores of his great and powerful country, but 

 also because he has come upon a mission 

 of grave consequence — so grave, indeed, 

 that he has deliberately set aside all pre- 

 cedent — to the civilisation of the world, 

 and to help in the settlement of the public 

 affairs of a continent plunged into a welter of 

 confusion unparalleled in the history of man. He 

 comes, though a participator, and in large measure 

 a determining factor, in the victorious issue of 

 the colossal efforts made to meet the imposing 

 onslaught on men's liberties on the part of a great 

 autocracy backed by all the immense resources of 

 modern science, with a message of reconciliation 

 and goodwill to the nations concerned in the 

 dreadful struggle of the last four and a half years. 

 We are all now confronted with the arduous duty 

 of laving the foundations of a new polity which 

 shall assure the means, through long years of 

 tribulation it may he, of a progressive, contented 

 life in harmony with the well-being- of humanity. 

 Mr. WiKon comes armed with the spirit of right 

 and justice; he will maintain the one and demand 

 the other, and he trusts to the essential power of 

 these two great principles to ensure the conditions 

 of a firm, just, and lasting peace. He has shown 

 himself, from the time lie led his nation into the 



