94: HYDRAULICS. 



the base and perpendicular height, whatever may be the 

 figure of the vessel. 



7. The pressure of a fluid on any kind of surface, hori- 

 zontal, vertical, or oblique, is equal to the weight of the 

 column of the fluid, the base of which is equal to the area 

 of the surface pressed, and the height of which is equal to 

 the distance from the surface of the fluid to its centre of 

 gravity, on the surface pressed. 



8. The side of a vessel filled with water sustains a 

 pressure equal to the area of the side multiplied by half 

 the depth, whether the sides be vertical, oblique, or hori- 

 zontal. 



9. If the vessel be tub-shaped, or in the form of an in- 

 verted frustum of a cone or pyramid, the bottom sustains 

 a pressure equal to the area of the bottom and the depth 

 of the fluid. 



10. The quantity of water that will flow out of a per- 

 pendicular slit or aperture from the surface of the head to 

 its base, is but two-thirds of what would flow out of a slit 

 of the same dimensions were it horizontal at the level of 

 the base. 



11. A circular pipe of the same area as a square^ trian- 

 gular, or irregular one, will discharge more water in a given 

 time. 



12. The greater the length of the discharging pipe, the 

 less the discharge, unless the pipe be perpendicular. 



