B. TERRESTRIAL PHYSICS AND 1UETE0R0L0GY. 47 



to our readers, agreeing, as they do, in the most essential 

 points, with the results of inquiries by the United States Sig- 

 nal Service. The author, after referring to the great amount 

 of statistical matter upon the subject of meteorology, and the 

 great number of persons interested, locally or otherwise, in 

 such inquiries, thinks that it may be considered as a matter 

 of surprise that so few have attempted the investigation of 

 the greater problems of meteorology, but suggests that this 

 is caused, in part, by the abstruse character of the inquiries 

 involved, and the almost interminable complexity of the con- 

 ditions which influence the motions of the atmosphere. In- 

 deed, so many are the difficulties in which the subject is in- 

 volved, that it requires a certain degree of scientific enthusi- 

 asm to believe that they are not insurmountable. 



One of the most important generalizations in regard to the 

 motion of the winds, according to Mr. Ley, is that known as 

 Ballot's Law, which connects the direction of every surface 

 wind with the distribution of surrounding pressures ; and he 

 thinks that the general fact that the winds blow in direc- 

 tions nearly parallel to the isobarics (or lines of equal atmos- 

 pheric pressure, as shown by the barometer), having the high- 

 est pressure on the right and the lowest on the left, in the 

 northern hemisphere, and the contrary in the southern, no 

 longer needs demonstration, being now an accepted law. It 

 is only recently, however, that its bearing upon some of the 

 earlier conceptions of the science has received attention. 



Among the general propositions which Mr. Ley presents to 

 his readers, and some of which he thinks he can prove, and 

 others of which require more or less further investigation, are 

 the following : 



I. Baric areas, or the atmospheric spaces inclosed in iso- 

 baric lines, tend, as a general rule, in temperate latitudes, to 

 circular or oval forms. These forms are most nearly ap- 

 proached in the areas of lowest pressure, while irregular fig- 

 ures are common in those of high pressure. 



II. Baric areas are naturally divided into two classes, viz. : 

 A, those whose currents revolve directly (or with watch- 

 hands) in the northern hemisphere, and the contrary in the 

 southern (" anti-cyclonic") ; and B, those whose currents re- 

 volve in a retrograde direction (or against watch-hands) in 

 the northern hemisphere, and the contrary in the southern 



