6 4 



DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



same direction as the numbers on the dial of fig. 32, the singular point will then 

 be called positive; or in the opposite direction, the singular point will then be 

 called negative. The eight diagrams of fig. 56 represent positive, the two of fig. 57 

 negative singular points, the successive diagrams are differing from each other by 

 the situation of the initial isogon, that represented by o or 64. The change from 



/g 



X' 



A 



2/ 



Fig. 56. Positive singular points of isogonal curves. 



A. Pure divergence. 



B. Anticyclonic spirals of northern hemisphere. 



C. Anticyclonic circles of northern hemisphere, cyclonic of south- 



ern hemisphere. 



D. Cyclonic spirals of southern hemisphere. 



E. Pure convergence. 



F. Cyclonic spirals of northern hemisphere. 



G. Cyclonic circles of northern hemisphere, anticyclonic of south- 



ern hemisphere. 

 H. Anticyclonic spirals of southern hemisphere. 



24 16 8 32 2t 



Fig. 57. Negative singular points of isogonal curves. 



diagram to diagram represents a rotation of the system of isogons of 45 . In all cases 

 we can draw the short lines across the isogonal curves, and then the vector-curves. 

 The diagrams will then show the features of the vector-field, which in the different 

 cases corresponds to the singular point in the field of isogonal curves. 



