20 HYDRAULICS AND ITS APPLICATIONS 



h being measured in feet. Fig. 8 A and B, shows such a gauge fitted to a 

 pipe conveying respectively airin A and water in B. in each 

 case marks the zero of the scale, and, in B, h measures the pressure at 



FIG. 8. 



the centre of the pipe, from which the pressure at any other point may 

 be calculated from purely statical considerations. If the pressure is so 

 great as to give an inconveniently long column of water, mercury (specific 

 gravity 18'596) may be used as shown in Fig. 8 C. If is the common 



