64 



SCIENCE 



[N. S. Vol. XLII. No. 1071 



States and cyclones are numerous in the 

 south. With the approach of summer, the cy- 

 clone paths move northward with the advance 

 of the sun. Thus, in summer, cyclones gen- 

 erally move along the northern border of the 

 United States. On account of this migration 

 of cyclone paths it is evident that the north- 

 erly and easterly types of weather are more 

 frequent in winter than in summer. 



Through the masterly treatment of his sub- 

 ject. Professor Ward makes an effective attack 

 on the tendency to describe climates without 

 a thorough consideration of the weather ele- 

 ment. 



TYPES OF STORMS OF THE UNITED STATES AND 

 THEIR AVERAGE MOVEMENTS^ 



This monograph by E. H. Bowie and E. H. 

 Weightman, of the Weather Bureau, consid- 

 ers the cyclones of the United States from the 

 forecaster's point of view. The 2,597 cyclones 

 shown on the morning and evening weather 

 maps for the years 1892-1912 inclusive are 

 here ably classified and discussed. The data 

 in the voluminous tables are also presented 

 on charts showing for each five degrees square 

 the number, direction and speed of movement 

 of storms classified by regions of origin and 

 by months. The West India cyclones are 

 strikingly portrayed on monthly maps show- 

 ing their average movements for each 24 de- 

 grees square. 



The discussion, although only ten pages 

 long, is well supported by the 21 years of cy- 

 clones and the writers' wealth of experience in 

 forecasting. The immediate control of the 

 types of cyclones and their movements is ap- 

 parently exerted by the subpermanent " high " 

 in the middle latitudes of the North Atlantic 

 and by the center of action knovra. as the 

 " Aleutian low." When the former is well 

 developed, the lows and highs usually move 

 along high latitudes; and stable temperatures 

 above the seasonal average are experienced 

 over the eastern half of the United States. 

 When the Aleutian low is well-developed and 

 south of its normal position, cyclones enter 



2 Mo. Weather Bev. Supplement, No. 1, 37 pp. ; 

 114 charts, November, 1914. 



and cross the United States in low latitudes 

 and are accompanied by stormy weather and 

 great alternations in temperatures. Appar- 

 ently, the cyclones entering the country from 

 the west and north are offshoots from this sub- 

 permanent low. 



The authors have indicated how the move- 

 ments of cyclones are apparently closely con- 

 nected with the temperature, wind, and rain 

 conditions in the vicinity of the cyclonic cen- 

 ter. Also the general pressure distribution 

 and pressure changes influence cyclones. 

 These connections are of direct value not only 

 to the forecaster but also to the meteorologist 

 studying the dynamics of cyclones. 



METHODS OF CLIMATIC PRESENTATION 



Equipluves or Isomers. — In the Scottish 

 Geographical Magazine, July, October and 

 November, 1914, and February, 1915,^ Mr. B. 

 C. Wallis has presented the monthly rainfall 

 of Africa, Australia and the eastern United 

 States by means of equipluves (lines which 

 show the rainfall in proportion of the annual). 

 The maps of Africa and Australia aiiord ex- 

 cellent examples of the value of this method. 

 In spite of the almost total lack of rainfall in 

 parts, the maps show the monthly importance 

 of the rain there as elsewhere. Thus the 

 swing of the tropical and subtropical rain 

 belts with the sun is shown more clearly than 

 on maps of actual rainfall. 



In the eastern United States the rainfall 

 intensity as well as the actual amount of pre- 

 cipitation depends on three factors: (1) the 

 " swing of the sun," which has its most marked 

 effect farthest from the sea; and is character- 

 ized by summer rains and winter dryness; (2) 

 the proximity of the ocean, which, by causing 

 heavy rainfall, makes to some extent the effect 

 of insolation; and (3) local temperature condi- 

 tions which have their most marked effect in 

 causing variations in the months of maximum 

 and minimum intensity of rainfall. 



Dr. H. E. Mill and Mr. Carle Salter, of the 

 British Eainfall Organization, have applied 

 much the same method to the study of the 



3 See also Mo. Weather Mev., January, 1915, pp. 

 11-24. 



