280 SUPPLEMENT TO CHAP. XIV. [CHAP. T. 



When the radius of curvature is very great with reference to the thick- 

 ness of the beam, and the relative change of length = is disregarded, 

 we have simply 



/Mds &d 

 BI H -- ; 



/Md 

 -jj-j- hence, for very small with 



reference to r, 



. . . . (15) 



We shall have frequent occasion to refer to formulae (8), (12), (18), (14) 

 and (15) in the following discussion. 



