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Dr. L. Silberstein : Further Contributions 



collinear with and P (fig. 2). In other words, the vectors 

 P, S differ only through tbeir tensor. Such being the case 



Fisr. 2. 



«V^ 



there is no objection against writing (2) in the form 



1-f (ab)=S/P, or also 



S-P OS- OP 



(ab) = 



UP 



. . (2a), 



In the next place we see from this equation (and from tlie 

 drawing) that when b = a. i. e. when a, b coalesce, and 

 therefore S = 2a, while P = a, we have 



(aa) =1. 



for any unit vector a. Similarly if b = a = — a, the vector S> 



