182 



Dr. C. Chree on Applications of Phyi 



In the case of symmetry shown in fig. 3, where the centre 

 of the rectangle lies on Ox, 



(OD + DM)/(OA -AM) = (OD + DM) 2 /OM 2 , &c, 



and (16 6) reduces to 



*V*m (i-V^, /OD + DM ON\ n „. 



Figl 



B 



M N 



! ^ 



r 



L M 





N 







X 



Tig- 3. 



D 



c 







,^-y 







H Af 



/r 



N 



X 



In this last case of course div/dy = 0, and Ox is the line of 

 greatest slope at 0. 



' If in fig. 3 we draw DH and CK, bisecting the angles 

 ODM OCN, we easily throw (17) into the elegant form 





(18) 



