DIRECT DRAWING OF THE LINES OF FLOW, ETC. 



49 



The singularities presented by the lines of flow are in a definite relation to the 

 field of intensity. As we have remarked already, wherever vector-lines intersect each 

 other under finite angles, the vector must have the numerical value zero. In the same 



Fig. 48. Simplest singularities in two-dimensional vector-field. 



A. Neutral point. 



B. Point of divergence, northern hemisphere. 



C. Point of convergence, northern hemisphere. 



D. Point of divergence, southern hemisphere. 



E. Point of convergence, southern hemisphere. 



F. Line of divergence. 



G. Line of convergence. 



manner the vector must have smaller numerical values in the asymptotic lines than 

 on both sides of it, because the components normal to the line disappear in the line. 

 Thus: 



The numerical value of the vector is zero in the singular points, and has a 

 relative minimum in the singular lines. 



