1922. No. 12. AX INVARIANT PROPERTY OF THE NOTION OF A DYADIC. 7 



But the matrix M is different from M, i. e. : consists of other quantities 

 (elements) than the matrix M. For from (16) we get: 



(21 ) a,- ■ fj = "^ ikfjk = akt eikfji = an enfji 



But here is : 



(22) /// = f/ • e/ = [f'jk e/) • e/ =/y-t ski 



which inserted in (21) gives: 



(23) Ô iiif jf. = an e,t ekif jk 

 That is: 



(24) ^ ik = en eki an 



Then we must consider the dyadic to be a much more general and 

 pliable notation for a transformation than the matrix. A dyadic is a notion 

 existing by itself and having absolute geometrical (as well as physical) signi- 

 ficance independent of any particular coordinate system. This point of view 

 has been asserted verv clearh' and con\incingly by Gustav J.vlmaxn '. 



Horten (Norway) September 1922. 



' See, for example, Gustav Jaumaxn : Über Dyaden undDyadenrcchnung, Arch. d. Mith. 

 u. Phys. 25. Bd., 1917. 



