On the Pri?idples of Pump-JVork, 225 



ftion "use, for they are faulty in many respects, particularly 

 the two following : 1 . They liave, in general, a great deal of 

 friction, to overcome which a part of the given force must 

 beapplied. 2. One half of the time employed in workiny; 

 them is lost : and since every moment of time is precious iii 

 a ship that has sprung a leak, it is evident a common pump 

 is by no means to be depended upon in any such pressinp- 

 exigence. These are two essential defects of structure; i 

 pass over all circumstantial ones that render their application 

 on ship-board every way improper. 



The effect of a pump is, with a given force, to raise the 

 greatest quantity of water to a given height, in the shortest 

 lime. From this defmition it follows, that cvcrv pump, or 

 hydraulic machine, which has any friction, or loses anv 

 water in its operation, must, in its own nature, be unfit for 

 all naval purposes. And that cme or the other of these deficien- 

 cies is inseparable from the structure of a chain-pump, must 

 be evident to every intelligent person; for, if the pallets 

 touch the pipe, there will be friction; and if they do not, 

 there will be loss of water, which is the same thing'as loss of 

 time. Therefore it is manifest a chain-pump cannot be 

 used in a ship without hazarding the loss of the ship, the 

 cargo, and the lives of all his majesty's subjects on board 

 the same. 



It will be in vain to allege any thing in favour of » 

 machine which is in its own nature bad, and of dangerous 

 consequence to be used; to say the lower part of the pipe is 

 so fitted to the pallets that the water raised cannot there run 

 out and be lost, is to confess^ friction; for no person who 

 understands the force and effect of the pressure of the atmo- 

 sphere, will pretend that any pu'.np or engine whatever can 

 be made water-tight, without friction to~ a degree superior 

 to the pressure of the aii'; since by the pressure of the air 

 the water endeavours to descend beiween the piston and the 

 barrel, which can only be prevented by the close application 

 of some springy substanceabout the piston, as cloth, leather, " 

 Sc';., producing the friction above mentioned. 



The chain-pump is not only subject to the friction of the 

 piston and water-pipe, but to much more besides, arising 

 Irom the two wheels and axles in each: from the comnjon 

 principles and experiments of mechanics, it appears that near 

 a third partof the power islostin mostmechamcal machines. 

 as being employed to overcome friction unavoidable in then- 

 structure ; and this impediment we shall in vain atten>pL to 

 remove by fjiction wheels in the chain-pump, whose eon- 

 Vul.'.'O. No. 79. D'c. IbOl. !» siruction 



