44 Arterial Drainage 
Fif. 6. — Modern Shadoof, or Pole and Bucket, used for raising ivatcr. 
human labour. Generally these water-wheels have been fitted 
up more with regard to simplicity and economy of cost than 
to an effective use of the motive power. Where water is 
plentiful, this may not be a consideration. A turbine will, 
however, be found a more compact and effective machine, 
and it has been extensively adopted on the Continent, but much 
less patronised in England than it deserves. The turbine is a 
water-wheel, having generally a vertical axis, to which motion 
is imparted by a column of water entering at the centre and 
passing off at the circumference. It can be worked ajt either 
high or low pressure. In the former case it is driven by a small 
body of water having a high fall, and therefore suitable for erec- 
tion in hilly districts where the supply of water is small and vari- 
able, and facilities' exist for the construction of reservoirs : the 
latter kind of machine is adapted for a large body of water having 
a low fall, in some cases not more than 9 inches.* Turbines 
require very little masonry in fixing, and can be worked with a 
useful effect of from 75 to 80 per cent. The illustration (Fig- 7) 
shows one of Messrs. J. and H. Gwynne's horizontal turbines, 
fixed for working a set of pumps or other machinery. 
* For a full dpscription of these macliines, see ' Spon's Engineering Dictionaiy,* 
Al t. " Turbine." 
