THE 



AMERICAN JOURNAL OF SCIENCE 



[THIRD SERIES.] 



Aet. I. — Contributions to Meteorology ; by Eltas Loomis, Pro- 

 fessor of Natural Philosophy in Yale College. Twenty-first 

 paper. With plate I. 



[Read before the National Academy of Sciences, April 21, 1885.] 



Direction and velocity of movement of areas of low pressure. 



In several former papers I have examined the direction and 

 velocity of movement of areas of low pressure. Since those 

 papers were written, the materials for these investigations have 

 been greatly multiplied, and I now present a summary of the 

 results which I have obtained after an extended examination 

 of the Signal Service observations, and of the observations made 

 in other parts of the world. 



The monthly maps of storm tracks, which are issued by the 

 Signal Service in connection with the International Bulletin 

 give a distinct idea of the general direction of movement of 

 areas of low pressure for all parts of the Northern hemisphere. 

 Plate I was formed by a combination of these monthly maps 

 for several years. It represents only a small part of the storm 

 tracks delineated on the monthly maps, and does not attempt 

 to represent the storm tracks of different regions in their relative 

 frequency, but it is Resigned to afford a specimen of all the im- 

 portant storm tracks delineated on the monthly maps for all 

 parts of the Northern hemisphere. 



Aii. Jotjr. Sci. — Third Series, Yol. XXX, No. 175. — July, 1885. 

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