1916] on Polarized Light and its Applications to Engineering 597 



the normal stress is that of compression at the extreme edge, and 

 undue stress is therefore thrown upon the remainder of the section, 

 to balance the total pull on the member. This is also indicated by 

 the lines of stress which have been plotted from the observations. 

 A much better shape is one devised by Berkeley, and the 



reason for its special excellence is, I think, clear from the picture 

 of its stressed condition which is before you, from which you 

 will see that the head is so proportioned that the principal 

 transverse section is wholly in tension (Fig. 14) and is much more 

 evenly distributed than before, while the elongated head allows a 



