STXESS OK STKAIN. 



8 9 



In considering the effect of the pressure due to the height 

 or head of water, or *' static head," exerted upon the inter- 

 ior surfaces of a cylindrical structure such as a stand-pipe, the 

 explanation given by Trautwine is so concise and clear that it 

 is copied here without further apology : 



" In the figure, which represents a vessel full of water, the 

 total pressure against the semi-cylindrical surface a v ^ m d k 

 and perpendicular to it, must be also horizontal, because the 

 surface is vertical ; but inasmuch as the surface is curved, this 



