HYDRAULICS. 



of which a solid cylinder b, of the same 

 length, but of only half the diameter or 



to. 



thereabouts, is made to revolve by its 

 axles passing through water-tight stuff- 

 ing boxes in the sides of the larger and 

 exterior cylinder. The internal cylin- 

 der does not revolve in the centre of the 

 large cylinder, but is so placed that one 

 of its convex exterior edges may come 

 into close contact with some one part 

 of the concave or internal surface of the 

 larger cylinder, as shown in the figure ; 

 and the circular exterior surface of the 

 small cylinder is equipped with four 

 metal flaps or valves c c c c, turning on 

 hinges, and partaking of its own curva- 

 ture, so that when they are shut down 

 or closed, they form no projections, 

 but appear as parts of the same cylin- 

 der. These flaps are made to open 

 either by springs placed underneath 

 them, or, what is still better, by two cross 

 wires, sliding through the internal cylin- 

 der in such manner that they may cross 

 each other exactly in its "centre, by 

 which their operation will be rendered 

 equable in every part of their revolu- 

 tion. From the formation of this ma- 

 chine,when one of these flaps is brought 

 by the revolution of the internal cylin- 

 der between itself and the external one, 

 it will be pressed down close and will 

 shut, but as the inner cylinder moves, 

 it will be earned into a continually 

 widening space until it arrives at a op- 

 posite to the last-mentioned situation, 

 when the cavity formed between it and 



the smaller and larger cylinder will 

 have so far increased as to form a va- 

 cuum, which is filled with water by the 

 feeding pipe e. This cavity is no sooner 

 so increased to its largest dimensions 

 than it is diminished by a continuation 

 of the revolution, in consequence of 

 which the water being pent up and 

 squeezed into less compass, makes its 

 escape by the delivering pipe/; and as 

 each of the flaps performs the same 

 operation in its turn, this pump affords 

 a very equable and constant supply of 

 water. The greatest difficulty in its 

 construction is, that of keeping the sides 

 of the flaps so packed as to maintain a 

 perfect contact with the sides of the 

 large cylinder without unnecessary fric- 

 tion, a* fault which equally holds good 

 in Mr. Bramah's fire-engine, in all ex- 

 centric pumps, and in all the rotatory 

 steam-engines that have yet been in- 

 vented. The Excentric Pump is of the 

 lift and force variety, since it will de- 

 liver water to an indefinite height above 

 its working cylinders. 



The fourth class or division of pumps, 

 or rather hydraulic machines for raising 

 water, consists of such engines as act 

 either by the gravity or weight of a por- 

 tion of the water they have to raise, or 

 of any other water that can be used for 

 such purpose, or by its centrifugal 

 force, momentum, or other natural 

 powers ; and this class, therefore, in- 

 cludes some very beautiful and truly 

 philosophical contrivances, too numer- 

 ous to be described in these limits : but 

 the Hungarian machine, the Centri- 

 fugal Pump and the Water-Ram offer 

 interesting examples of the general na- 

 ture and construction of the machines 

 which are placed under this division. 



The Hungarian machine, so called 

 from its having been employed in drain- 

 ing a mine at Chemnitz, in Hungary, 

 produces its action by the condensation 

 of a confined portion of air produced by 

 the descent of a high column of water 

 contained in a pipe, and therefore acts 

 with a force proportionate to the weight 

 of such column. Its general form is 

 shown at/^. 14, by which it will appear 

 that it is an exceedingly simple and use- 

 ful machine, admitting of many modifi- 

 cations and applications, but it can be 

 used only in hilly countries, or situations 

 where the source of water by which it 

 is to be worked is as much above the 

 top of the well, as the water to be raised 

 is underneath it. In this figure a is 

 supposed to be a well or the shaft of a 

 c 



