and the Storage of Water. 
33 
densing-engines. The fans of the pump are 7 feet in diameter. 
The lift is 5 feet, and with this head the two pumps can dis- 
charge 700 tons of water a minute.* 
The defect of the scoop-wheel is that it cannot adapt itself to 
variations in the level of the water in flood times, either on the 
delivery or inlet side. It cannot be driven beyond a certain 
speed, and if deeply immersed in water it does very bad duty. 
It is much more cumbrous than a centrifugal pump, and conse- 
quently requires more expensive foundations. The relative pro- 
portions of a scoop-wheel and a pump to deliver water, say with an 
11-feet lift and engine of 14 horse-power, would be as follow: 
diameter of scoop-wheel 40 feet, width 18 inches, number of 
revolutions 4J. Diameter of pump 3 feet 4 inches, width 8j 
inches, number of revolutions 180. Centrifugal pumps employ 
advantageously the whole power of the engine ; as the lift de- 
creases, so the quantity of water discharged increases, and that 
in an automatic manner, without any sensible alteration in the 
speed of the engine, and without any care on the part of the 
attendant. It is found in practice that centrifugal pumps do keep 
the land clear with less horse-power, and therefore less fuel per 
acre, than scoop-wheels. In a comparative trial in six districts 
drained by pumps and scoop-wheels respectively, the area drained 
ranged in the case of pumps, from 1000 to 1228, and in the case 
of scoop-wheels from 600 to 830 only per unit of power em- 
ployed. f The illustration (Fig. 5, p. 34) shows a pump and engine 
attached to an iron cylinder, as manufactured by jVIessrs. Eastons 
and Anderson, and peculiarly well adapted for fixing in peat 
soils, where it is difficult to secure a good foundation without 
great expense. 
At a rough calculation, it may be assumed that for the drainage 
of fens or low-lying districts, from 1 to 1^ horse- power will 
be required for every 100 acres where the lift does not exceed 
10 feet. 
Dumb Wells. — Where the nature of the subsoil is of a porous 
and absorbent character, as chalk, limestone, or some sort oi 
sandstone, the quantity of water discharged in flood times may 
be regulated by dumb wells sunk into the porous strata. By 
means of these shafts the capacity and cost of new arterial 
drains may be reduced, and flooding prevented without altering 
existing water-courses. In the illustration, Fig. 1, p. 11, a shaft 
sunk through the impermeable strata, between the letters B 
* ' History of the Fens of South Lincolnshire.' By W. H. Wlieeler, C.E. 
Sinipkins and Co., 1868. ' Trans. Instil. Civil Engineers,' vol. xxxiii. ; Engineer- 
ing, Sept. 18 and 25, 1869. 
t Paper by J. M. Heathcote, Esq., in the ' Cambridge Independent Press,' 
Nov. 24, 1877. 
VOL. XIV. — S. S. D 
