132 FERGUSON'S LECTURES. 



LECT. other part besides that in which the piston works, does 

 .^v-^/ not make the pump either more or less difficult to work, 

 except what difference may arise from the friction of 

 the water in the bore ; which is always greater in a 

 narrow bore than in a wide one, because of the greater 

 velocity of the water.* The pump-rod is never raised 

 directly by such a handle as E at the top, but by means 

 of a lever, whose longer arm (at the end of which the 

 power is applied) generally exceeds the length of the 

 shorter arm five or six times ; and, by that means, it 

 gives five or six times as much advantage to the power. 

 Upon these principles, it will.be easy to find the dimen- 

 sions of a pump that shall work with a given force, and 

 draw water from any given depth. But, as these calcu- 

 lations have been generally neglected by pump-makers, 

 (either for want of skill or industry) the following table 

 was calculated by the late ingenious Mr. Booth for their 

 benefit. In this calculation, he supposed the handle 

 of the pump to be a lever increasing the power five 

 times ; and had often found that a man can work a 

 pump four inches diameter, and 30 feet high, and dis- 

 charge 27i gallons of water (English wine measure) in a 

 minute. Now, if it be required to find the diameter of a 

 pump, that shall raise water with the same ease, from 

 any other height above the surface of the well ; look 

 for that height in the first column, and over-against it, 

 in the second, you have the diameter or width of the 

 pump ; and in the third, you find the quantity of water 

 which a man of ordinary strength can discharge in a 

 minute. 



Note 40. Should the disproportion between the suction-pipe and 

 piston-barrel be very considerable, the labour of working the pump 

 will be materially increased. Instances, however, have occurred, in 

 which pumps have been so constructed as to raise cannon-balls by 

 the momentum of the ascending column of water ; uud when hydraulic 

 engines are constructed for the use of vessels, this mode of increasing 

 the velocity of the water appears well adapted to prevent the pump 

 choking or becoming foul. 



