DYNAMIC METEOROLOGY. 



361 



coming- volume IV of the Memoirs of the National Academy of Science. 

 Ah ail early eoi)y of the i)rivate edition has fallen into the hands of Brs. 

 Van Bebber and W. Koeppen, the latter has given a condensed review 

 of both chapters more perspicuous than the mass of details given in the 

 original. We shall do our readers a favor by laying this before them; 

 and the more so inasmuch as the labor bestowed by Koeppen and his 

 occasional criticisms as reviewer enhance the value of his work. This 

 constitutes a most condensed summary of the results to dynamic meteor- 

 ology of the statistics published daily by the U. S. Signal Service. 



Barometric maxima. — The isobars around a barometric maximum 

 are of irregular, more or less elliptical, form. The ratio of the greatest 

 to the least axis of the ellipse, as determined by Loomis from three years' 

 observations for North America, for Europe and the Atlantic Ocean, is, 

 respectively, 1.91 for 238 cases in North America, and 1.81 for 252 cases 

 in Europe and on the Ocean. In a third of all these cases this ratio was 

 more than 2. The same number is also found by Loomis for the ratio 

 of the similar axes in areas of barometric minima. The direction of the 

 longest axis with reference to the meridian is also demonstrated to vary 

 very little in the two regions, being as shown in the accompanying 

 table : 



The more easterly direction of the axes of the minima on the ocean 

 and in Europe is by Loomis attributed to the frequent formation of a 

 ridge of high pressure which in the colder half of the year connects the 

 area of high pressure in Asia and the Azores. Three-fourths of the 

 above cases are of this kind. 



Loomis subjects to a special investigation the especially intense baro- 

 metric maxima. He collects these in three tables, of which the first one 

 (Loomis No. XL) contains all cases in which, during the years 1872 to 

 1884, a pressure of over 30.85 inches (783.6 millimeters) occurs at any 

 station of the United States on the charts of the Signal Service; the 

 second table (Loomis LVi) contains the cases in which, during the years 

 1874, 1876, and 1881, an isobar of 785 millimeters occurs on the Hoti- 

 nieyer charts, and their continuation by the Seewarte; the third table 

 (Loomis LViii) contains those cases in which, during the interval from 

 1877 to the beginning of 1884, an isobar of 31 inches (787.4 millimeters) 

 occurs on the charts of the International Bulletin of the Signal Service, 

 which comprehends the whole northern hemisphere. 



The anmial diiitrihut ion of these cases is given by the following tabular 

 summary ; in whi(;h, of the double numbers, the first one gives the num- 



