29:2 Hydrostatics. 



Fig 192. 4 ^ 8t Let us now suppose that the vessel ABCD, being closed 

 on all sides, is filled with a fluid destitute of gravity, and that, 

 having a very small opening at , we apply to it any force ; it 

 is evident that the pressure that would hence be exerted upon 

 the plane surface represented by BC, would not depend in any 

 degree upon the quantity of fluid contained in the vessel, nor 

 upon the figure of the vessel ; but that, since the pressure applied 

 at E transmits itself equally in all directions, the pressure upon 

 BC would be equal to that exerted upon any point of the opening 

 JC, repeated as many times as there are points in BC. 



409. For the same reason, the pressure applied at E, trans- 

 mitting itself in all directions, would tend to raise the superior 

 surface AD^ and the force thus exerted would be for each point 

 equal to the pressure applied at any point of the opening E ; so 

 that the surface J1D is pressed perpendicularly from within out- 

 ward with a force equal to the pressure employed at any point 

 of the opening E, repeated as many times as there are points 

 in AD. 



Fig. 193. 41 * Let the vessel ABCDEF, the part CD being horizontal, 

 be filled with a heavy fluid. We say that the pressure upon the 

 bottom CZ), arising from the gravity of the fluid, does not depend 

 upon the quantity of fluid contained in the vessel, but simply 

 upon the extent of CZ), and its depth below the surface AF. 



To make this evident, let us suppose, the line BE being hor- 

 izontal, that the fluid contained in BCDE, is suddenly deprived 

 of its gravity, it is evident that a vertical filament IK, of heavy 

 particles of the fluid contained in ABEF, would exert at the 

 point K a pressure which must diffuse itself equally throughout 

 the whole extent of the fluid BCDE that this pressure would be 

 40 exerted with equal force from below upward to repel the action 

 of each of the other vertical filaments belonging to the several 

 points of BE ; hence the filament IK effects, by itself, an equili- 

 brium with all the other filaments of the mass ABEF '; therefore 

 the mass BCDE being destitute of gravity, there w r ill result no 

 other pressure on the bottom CD, than that arising from the fil- 

 ament IK, which transmitting itself equally to all the points of 

 CD causes upon CD a pressure equal to that exerted at the 



