HYDRAULICS. 



9 



The Bucket-Engine and Chain-Pump 

 are but modifications of the above-de- 

 scribed machines, and are very useful in 

 particular situations. The chain-pump 

 is shown at fig. 6, and consists of a 

 number of fiat plates or discs of wood 

 or metal d d d, which are usually square, 

 and are connected together through 

 their centres by an iron rod, with joints 



between each board, so ac to permit 

 them to turn with nearly the same free- 

 dom as if they were connected by a 

 chain. The chain of plates so formed is 

 supported and kept in its place by two 

 wheels e and f, each being furnished 

 with double projecting arms to lay hold 

 of, and support the plates in succession, 

 and in such manner, that if the upper 

 wheel e is turned by a winch, it will 

 cause the whole chain to move, one side 

 of it passing upwards, while the other 

 descends continually in the same direc- 

 tion. The ascending side of the chain 

 is made to pass through a consider- 

 able length of square box or trunk 

 which, by fitting pretty closely to the 

 plates, forms the pump. The lower 



wheel/, as well as the lower end of the 

 trunk, must be under water, and the 

 chain of plates passing upwards through 

 the trunk, produces a succession of 

 chambers or cavities that become filled 

 with water, which is eventually dis- 

 charged from the top. From the for- 

 mation of this pump, it requires to work 

 in deep water, and consequently cannot 

 drain a reservoir to the bottom ; but it 

 has the advantage of not being liable to 

 choke, and will even bring up mud, 

 stones, and such weeds and chips, as 

 would entirely destroy the operations of 

 a more perfect machine ; and notwith- 

 standing it may be supposed to lose 

 much of its power, owing to the plates 

 not fitting very accurately into the tiunk, 

 yet as an upper chamber can only leak 

 into one that is below, and the motion 

 of the plates is very rapid, it will, when 

 properly constructed, bring up a very 

 considerable quantity of water ; and it 

 is, on this account, more frequently used 

 than any other sort of pump, in drain- 

 ing the water from foundations, in the 

 construction of bridges, docks, and large 

 works. If the top and bottom wheels e 

 and /are supposed to be retained, while 

 the trunk is taken away, and a num- 

 ber of buckets, similar* to those upon 

 the wheel (fig. 4.), are attached to the 

 chain, instead of the square plates ddd, 

 then the machine becomes a bucket-en- 

 gine, which is but another form of the 

 Persian wheel already described. There 

 are many more machines of this class 

 for raising water, but the examples al- 

 ready given embrace the principles of 

 most of them, and it would be quite be- 

 yond the limits of this work to attempt 

 to describe the whole of them. 



The Pope-Pump of Vera, described 

 in most books on Hydraulics, consists 

 likewise of an upper and lower pulley, 

 formed in the ordinary manner, but with 

 several grooves in each, in which end- 

 less ropes of very loosely spun horse- 

 hair or wool are" made to move with 

 great rapidity by a multiplying wheel 

 connected with the upper pulley. The 

 lower pulley, together with a great part 

 of the rope, moves in the water, which 

 is merely brought up by adhering to the 

 ropes and the rapidity of their motion. 

 This, therefore, is but a very imperfect 

 and rude kind of bucket-pump, and is 

 by no means deserving the place it has 

 so long held in the catalogue of Hy- 

 draulic machines. 



The second class of contrivances for 

 raising water, or that in which they act 



