HYDROSTATICS. 



clearly understood by an inspection of the follow 

 ing figures. If water be poured into the tube A, 



(Fig. 1.) it will run through the honzonta. tube 

 E, and rise in the opposite tube B, to the same 



nright a. which it stands at A. It is on this 

 orinciple that water is now conveyed under 

 ground, through conduit pipes, and made to rise 

 to the level of the fountain whence it is drawn. 

 The city of Edinburgh, a considerable part of 

 which is elevated above the level of the surround 

 ing country, is supplied with water from a reser 

 voir on the Pentland hills, several miles distant. 

 The water is conveyed in leaden pipes down the 

 jeclivity of the hill, along the interjacent plain, 

 and up to the entrance of the castle, whence it is 

 distributed to all parts of the city. If the point 

 A represent the level of the reservoir, C D will 

 represent the plain along which the water is con 

 veyed, and B the elevation to which it rises on 

 the castle hill. On the same principle, and in 

 a similar manner, the city of London is supplied 

 with water from the water-works at London 

 bridge. Had the ancients been acquainted with 

 this simple but important principle, it would 

 have saved them the labour and expense of rear 

 ing those stupendous works of art, the aqueducts, 

 which consisted of numerous arches of a vast 

 size, and sometimes piled one above another. 



Fig. 2. represents the syphon, the action of 

 which depends upon the pressure of the atmos 

 phere. If this instrument be filled with water, 

 or any other liquid, and the shorter leg, G, 

 plunged to the bottom of a cask, or other vessel, 

 containing the same liquid, the water will run 

 out at the longer leg, F, till the vessel be emptied, 

 in consequence of the atmospheric pressure upon 

 the surface of the liquid. On this principle, 

 water may be conveyed over a rising ground to 

 any distance, provided the perpendicular height 

 of the syphon above the surface of the water in 

 the fountain does not exceed 32 or 33 feet. On 

 the same principle are constructed the fountain 



J&amp;gt; 



at command, the cup of Tantalus, and oiher en 

 tertaining devices. The same principle, too, 

 enables us to account for springs which are some 

 times found on the tops of mountains, and for 

 the phenomena of intermitting springs, or those 

 which flow and stop by regular a/ternations. 



(2.) Any quantity of fluid, however small, 

 may be made to counterpoise any quantity, however 

 large. This is what has generally been termed 

 the Hydrostatical Paradox ; and from this princi 

 ple it follows, that a given quantity of water may 

 exert a force several hundred times. greater or 

 less, according to the manner in which it is em 

 ployed. This force depends on the height of the 

 column of water, independent of its quantity; for 

 its pressure depends on its perpendicular height. 

 By means of water conveyed through a very 

 small perpendicular tube, of great length, a very 

 strong hogshead has been burst to pieces, and 

 the water scattered about with incredible force. 

 On this principle, the hydrottatic press, and other 

 engines of immense power, have been con 

 structed. 



(3.) Every body which is heavier than water, 

 or which sinks in it, displaces so much of the water 

 as is equal to the bulk of the body immersed in the 

 water. On this principle, the specific gravities, 

 or comparative weight, of all bodies are deter 

 mined. It appears to have been first ascertained 

 by Archimedes, and, by means of it. he deter 

 mined that the goWen crown of the king of Sy 

 racuse had been adulterated by the workmen. 

 From this principle we learn, among many other 

 things, the specific gravity of the human body ; 

 and that fo,ur pounds of cork will preserve a per 

 son weighing 135 pounds from sinking, so that 

 he may lemain with his head completely above 

 water. 



