E. Loomis — Results from an examination of the 



2. Atlas des mouvements generaux de I'atmosphere, redige 

 par I'observatoire Imperial de Paris, embracing 18 months, 

 from June, 1864, to Dec. 1865. 



3. Cartes synoptiques journalieres construites par N. Hoff- 

 meyer, Copenhagen, embracing 9 months, from Dec. 1873 to 

 Aug. 1874. 



In order to determine what may be called the average track 

 of storm centers in the United States, I ruled a large sheet of 

 paper with several vertical columns headed 122°, 117°, 107°, 

 etc., these numbers denoting degrees of longitude from Green- 

 wich. I then took one of the monthly maps showing the tracks 

 of storm centers, and following each of the tracks in succession 

 determined in what latitude it crossed the meridians indicated 

 at the top of the table, and the results were set down in the ap- 

 propriate column. I proceeded in the same manner with each 

 of the monthly maps and then took the average of all the 

 numbers in each column. The results are shown in the first 

 two columns of the following table ; where column first shows 

 the meridians of longitude from Greenwich, and column sec- 

 ond shows the average latitude in which each of these meridians 

 is intersected by the storm paths. The curve thus determined 

 is traced on the accompanying chart and passes over the center 

 of Lake Erie. It will be seen that the average direction of 

 storm paths is not the same on all meridians. The directions 

 given in my former article (see this Jour., vol. x, p. 1) must he 

 understood to be the average direction of storm paths for the 

 region covered by the United States observations ; and this 

 represents pretty nearly the mean direction for a place whose lat- 

 itude is 42-|° and longitude 83^° W., which is nearly the posi- 

 tion of Detroit, Michigan. 



Average direction of storm-paths. 



U.S.Weat 



erMaps. 



Parte M« 



B. 



Danish Ma 



P8. 



Mean of Par 



and Dan. 



h^Wn^K. 



Latttnde 



f^o°^«f. 



t^u^dt 



rhXX 



full: 



^«^1 





122° W. 



45-8" 

 46-9 



60°-45°W. 



462° 



6J°-50"W. 



tix 



55° W. 



ll'X 











40 -30 













15- 





30-20 



62-6 





54-9 



87 





-15 E. 





20-10 

















10-0 













30-45 





-10 E. 





5 E. 





62 









10-20 

 20-30 

 30-40 



ii:i 



25 



66-8 









150 -60 E. 



65-3 



55 E. 



53-3 



I proceeded in a somewhat similar manner with the Paris 

 maps, but since these maps do not generally exhibit lines 



