94 HYDROSTATICS. 



whatever the form or position of the sides may be, 

 and so on in proportion for greater or lesser depths ; 

 and if the sides are perpendicular, whatever be the 

 shape, that is, provided the width of the vessel is the 

 same all the way down, the pressure on every square 

 inch of the sides is nearly 1 3 pounds, at the depth of 

 30 feet, and so on in proportion for greater or lesser 

 depths. 



The Hydraulic Press. 



Pascal demonstrated this principle and its advan- 

 tages, by fixing to the upper end of a cask set up- 

 right, a very long and narrow cylinder. In filling 

 the barrel and afterwards the cylinder, the simple 

 addition of a pint or two of water, which the latter 

 was capable of containing, produced the same effect 

 as if the cask, preserving its diameter throughout, 

 had its height increased by the whole length of the 

 cylinder. Thus the increase of weight of a pint or 

 two of water, was sufficient to burst the bottom of 

 the hogshead, by the immense augmentation of pres- 

 sure it occasioned. , 



Now, if we suppose the water removed from the 

 cylinder of narrow dimensions, and replaced by a 

 solid of equivalent weight, such as a piston, it is 

 evident that the pressure must remain every where 

 the same. 



Again, if we suppose the weight of the piston to 

 be multiplied by the power of a lever acting on its 

 shaft, the pressure will be proportionally augmented, 

 so as to produce on the bottom of the cask a pressure 

 equivalent to an enormous weight, with the exertion 

 of very little primitive force on the piston. 



Lateral Pressure. 



The pressure on the side of a vessel is equal to 

 the weight of a column of w r ater equal to half the 

 perpendicular height of the vessel. 



