ON HYDROSTATICS. v 263 



or pyramidical vessel, full of water, is three times as great as the weight of 

 the water, since its content is one third of that of a column of the same 

 height, and standing on the same base. (Plate XIX. Fig. 243.) 



In this manner the smallest given quantity of any fluid contained in a pipe 

 may be made to produce a pressure equivalent to any given weight, however 

 large, which rests on the cover of a close vessel communicating with the 

 pipe, and this may be done either by diminishing the diameter of the pipe, 

 and increasing its height, while the weight is supported by 'a surface of 

 a certain extent, or by increasing the magnitude of this surface, without 

 adding to the height of the pipe; for in either case the ultimate force of the 

 fluid, in supporting the weight, will be equal to the weight of a column of 

 the same height, standing on the whole surface which is subjected to its action. 

 And if the effect of the column be increased by any additional pressure, in- 

 dependent of its weight, that pressure may be represented by supposing the 

 height of the column to be augmented ; and the effect of the additional pres- 

 sure will also be increased in proportion to the magnitude of the surface 

 which supports the weight. It is on this principle that the pressure of water 

 has been applied, by Mr. Bramah, to the construction of a very convenient 

 press. (Plate XIX. Fig. 244.) 



Although this property of fluids is the cause of some results which would 

 scarcely be expected by a person not accustomed to reflect on the subject, 

 and has, therefore, not improperly, been called the hydrostatic paradox, yet 

 it depends wholly on the general and acknowledged principles of mechanical 

 forces; nor can we agree with those authors, who have asserted, that a very 

 small quantity of a fluid may, " without acting at any mechanical advantage" 

 whatever, be made to balance a weight of any assignable magnitude : for 

 the immediate operation of the force very much resembles, in the most com- 

 mon cases, the effect of a wedge, or^of a moveable inclined plane ; thus, a 

 wedge remains in equilibrium, when the forces acting on each side are in pro- 

 portion to its length, like the hydrostatic pressure on a vessel of a similar form. 

 The conditions of the equilibrium of fluids may also be determined, in all cases,, 

 from the general law of the descent of the centre of gravity to the lowest point. 

 Thus, it is easy to show that even when two branches of a tube are of 



