HYDROSTATICS. 



small quantity of water has settled, 

 and is confined to the extent of a square 

 yard on the ground near the founda- 

 tion, and suppose it to fill up the whole 

 vacant space or crevice of no more than 

 half an inch deep, between the ground 

 and some part of the masomy ; if you 

 take a tube, however slender, of twenty 

 feet long, and thrust it down into the 

 water, and then fill it with water from 

 above, you apply a force or pressure 

 equal to six tons under a space of only 

 a yard square of the building, and 

 destroy it as easily as if you had mined 

 it with gunpowder. This may be easily 

 tried with a hogshead or butt of water, 

 or any other liquid, by fixing a small 

 strong pipe in the bung-hole, and 

 pouring water through it ; when the 

 water rises in the pipe to a sufficient 

 height (and this will be more or less 

 according to the strength of the barrel), 

 the ban-el will burst, although but a 

 very small quantity of water may have 

 been poured into the pipe ; for the 

 pipe may be of an extremely small bore, 



fig 



its width being wholly immaterial. One, 

 twenty feet long, was found to burst a 

 hogshead with great violence. 



The same effect may be produced 

 naturally by the rain falling into and 

 filling some long narrow chink that 

 may have been left in the walls of a 

 building, or may be made by its decay 

 in the course of time ; and whether the 

 chink be equally wide throughout, or 

 vary in its size, and whether it be 

 straight like a pipe, or crooked, makes 

 no difference : provided it is water-tight, 

 so as to get full of the rain, the pres- 

 sure will always be in proportion to 

 its perpendicular height, and not to 

 its length if it winds. The same pro- 

 cess in nature may produce the most 

 extensive devastation ; it may cause 

 earthquakes, and split or heave up 

 mountains. Suppose, in the bowels of 

 some mountain, (Jig. 8.) there should be 

 an empty space of ten yards square, and 

 only an inch deep on an average, in 

 which a thin layer of water had lodged 

 so as to fill it entirely ; and suppose, 



that, in the course of time, a. small 

 crack of no more than an inch in dia- 

 meter should be worn from above, 200 

 feet down to the layer of water ; if the 

 rain were to fill this crack, the moun- 

 tain would be shaken, perhaps rent in 

 pieces with the greatest violence, 

 being blown up with a force equal to 

 the pressure of above 5022 tons of 

 water, though not above a ton and 

 a half altogether had been actnally 

 applied. The same thing would happen 

 if any one on the spot where there is 

 such a layer of water below ground 

 should bore down in sinking a well, or 

 seeking for a spring, and then fill the 

 tube with water ; it is impossible to fix 

 the limits to the convulsion which 



might ensue. This prodigious power 

 however may be employed safely, and 

 even beneficially. In the operations of 

 nature, it is probably an important 

 affent, though it has not been suffici- 

 ently attended to by philosophers in 

 their attempts to explain natural ap- 

 pearances ; and it is capable of being 

 applied advantageously in the opera- 

 tions of art. It may plainly be used 

 with great effect in mining. On a 

 smaller scale, and as a power in ma- 

 chinery, it may certainly be employed 

 far more extensively than it has hi- 

 therto been. A tube of a yard long, 

 acting on a cavity of a yard square, 

 will give a pressure equal to the weight 

 of | of a ton avoirdupois, if used 



