88 



DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



Tables L. Graphical addition of mutually normal vectors. 



I. Table for drawing the intensity field F = \ A 2 -\-B z (B or A tabulated). 



II. Table for drawing the field of the angle ip a between the vector-sum F and the vector- 

 addend A (B or A tabulated). 



We shall first treat the case in which the two given vectors A and B are normal 

 to each other. The problem of their addition may then be considered as inverse 

 to the problem of solution into rectangular components treated in the preceding 

 section. It will be precisely inverse if the two vectors A and B are given in the form 

 used for components along orthogonal coordinate-curves, i. e., by equiscalar curves 

 for positive and negative values of the intensity. On the other hand, it will take a 

 slightly changed form if the vector is given in the ordinary way by isogons and inten- 

 sity curves for an always positive intensity. We shall treat this case only. It 

 will easily be seen that in the other case we can use the same tables, only with a 



