HYDRAULICS. 



would therefore discharge five times as 

 much water as the former, although 

 only twice the diameter ; a circumstance 

 that requires the serious attention of all 

 such as are practically concerned in the 

 construction of pumps, or distribution 

 of water through pipes for any pur- 

 poses. 



CHAPTER II. 



Of the various Pumps, Engines, and 

 Machines for raising Water. 



HAVING, in the preceding Chapter, 

 laid down the fundamental principles 

 upon which the motions of fluids de- 

 pend, and shown how they are acted 

 upon by the natural effects of gravita- 

 tion, the next object will be, to show 

 how their gravitation may be overcome 

 with the greatest advantage ; and how 

 water may be raised, and made to move 

 in various directions, to supply the 

 wants of man. This division of the 

 subject is of the greatest practical uti- 

 lity, as embracing an account of the va- 

 rious pumps, engines, and machines, 

 which have, from time to time, been in- 

 vented and constructed for this purpose ; 

 and numerous as they may appear to be, 

 yet it will be found that they are all 

 comprehended under four general heads; 

 viz. those machines in which water is 

 lifted in vessels, by the application of 

 some mechanical force to them ; those, 

 in which it is raised by the pressure of 

 the atmosphere ; those which act by 

 compression on the water, either imme- 

 diately, or by the intervention of con- 

 densed air ; and those which act by the 

 weight and momentum of the water, of 

 which they raise a part. 



The earlier hydraulic machines ap- 

 pear to have been constructed on the 

 first or simplest principle, with the ex- 

 ception of the pump of Ctesebes of 

 Alexandria, who flourished about one 

 hundred and twenty years before Christ, 

 but respecting the particular construc- 

 tion of which little appears to be 

 known. Probably, the first process re- 

 sorted to, was the common bucket and 

 rope, either raised by the hands, or 

 drawn up by a windlass, as in our com- 

 mon draw-wells ; but as such a process 

 is very tedious in deep wells, and even 

 expensive, if performed by manual la- 

 -bour, it would easily be improved by the 

 employment of animal strength to a 

 greater load, such as using several 

 buckets, at different heights, on the 

 same rope or chain ; which approxi- 



mates very closely to the more modern 

 bucket-engine and chain -pump. Ac- 

 cordingly, two of the most ancient hy- 

 draulic engines are on this principle ; 

 viz. the Persian Wheel, and the Arehi- 

 median Screw. 



The Persian Wheel, shown at/g-. 4, 

 must be of greater diameter, than the 

 height to which it may be necessary to 

 raise the water, and must stand in the 

 stream or reservoir from which the wa- 

 ter is to be taken ; it consists of a rim 

 or circle of wood, supported by arms or 

 spokes from the central axis or gudgeon 

 m, upon which the wheel revolves in a 

 vertical direction. Upon its circumfer- 

 ence a number of buckets or boxes, as 

 n, o,p, and q, are hung by iron loops 

 upon round iron bolts, in such a man- 

 ner, that these boxes may constantly 

 hang upright as the wheel revolves, and 

 since the lower boxes n n are con- 

 strained, by the motion of the wheel, to 

 dip into the w T ater r, they will become 

 filled, and \vill carry up their charge of 

 water as at o o o, until at length arriving 

 at the highest point p, they all in suc- 

 cession come into contact with the cis- 

 tern *, by which they are tilted up, and 

 discharge their contents into it, and hav- 

 ing passed over it, they descend on the 

 opposite side q q in an empty state, and 

 are ready to be filled again by dipping 

 into the water. Motion may be given 

 to this wheel, either by the power of ani- 

 mals, or, if r is a running stream with 

 sufficient water to spare, by equipping 

 the circumference of the wheel itself 

 with vanes or float-boards similar to 

 those of the wheel of any water-mill, in 

 which case it will raise up a portion of 

 that water by which it is itself driven 

 round. Small springs 1 1 are fixed to 

 each of the buckets, at that part which 

 comes into contact with the side of the 

 cistern s, for the double purpose of 

 breaking the violence of the blows 

 which the buckets would otherwise give 

 to the cistern, and likewise for more 

 effectually tilting the buckets to enable 

 them to completely discharge their con- 

 tents. Simple as this machine may ap- 

 pear to be, yet it is one of the most 

 cheap and effectual that can be put up 

 for irrigating land for farming or gar- 

 dening purposes, where it may be neces- 

 sary to raise a part of the water of a 

 running stream into a higher situation. 

 It requires no care or attendance while 

 working, and as it moves incessantly 

 while the stream runs, it will cany up a 

 very considerable quantity of water. 



