HYDROSTATICS AND HYDRAULICS. 4* 



cause the balance to rise ; then, by observing the loss of 

 weight, and proceeding as before, the specific gravity 

 may be obtained. Fragments of diamonds, &c., are put 

 into a glass bucket, and suspended from the scale. For 

 finding the specific gravity of fluids, a solid glass bubble 

 is used. 



From the near connexion between Hydrostatics and 

 Hydraulics, many writers have considered them one sci- 

 ence; yet it appears more systematic to treat of them 

 separately, and to rank under the head of Hydraulics 

 whatever is effected by the motion of water, as mills, 

 pumps, fountains, &c. 



One of the first principles of the science of Hydraulics 

 is, that fluids rise to their own level ; and thus they may 

 be conveyed over hills and valleys, by means of pipes, 

 to any height not greater than the level whence they 

 flow. With this property the ancients were unacquainted, 

 or they would not have formed those immense aqueducts, 

 the remains of which still exist in many places. If the 

 ancients wanted to convey water from one hill to another, 

 they often connected the hills by archways, and con- 

 trived that the water should flow over them ; while we 

 should effect the same by simply laying down a pipe or 

 series of pipes. A very great part of London is supplied 

 with water by pipes from the reservoir at Pentonville. 

 Jets, or fountains, are on this principle ; the water, by 

 endeavouring to rise to its level, spouts out in the 

 pleasing manner often witnessed. It will not rise quite 

 as high as its source, from its being impeded by the 

 resistance of the air, and the friction at the opening of 

 the pipe. 



If it be required to raise water above its level, it is 

 done either with a common Sucking Pump, by removing 

 the atmospheric pressure, or by the Forcing Pump. A 

 column of air of the height of the atmosphere of any 

 base, will counterbalance a column of water of the same 

 base, and of about 3<2 or 33 feet high; the weight of 

 each being alike. On this principle it is that the suck- 

 ing pump acts ; the air is exhausted from the bore of 

 the pump by means of a piston, acting in a manner 

 similar to a syringe ; the water rises, and passing through 



