46 
Arterial Drainage 
the larger ball out of its muzzle, and raises it to the orifice, which 
it immediately stops. 
Fig. 8.— T^e Hydraulic Bam. ^he momentum of 
the water raises the 
other valve, and the 
force of the water, 
compressing the air, 
is driven up the sup- 
ply-pipe. The ball 
soon loses the ve- 
locity imparted to it, 
and descends by its 
own weight, when 
the same process is 
again repeated. A 
full description of 
the different kinds of 
ram will be found in 
Tomlinson's ' Cyclo- 
paedia,'* under the ar- 
ticle " Hydrostatics." 
There are many cases, however, where the supply can only 
be obtained from a reservoir or water-course situated at a lower 
level than the locality to be supplied, and without sufficient 
fall to work an hydraulic engine. In this case the most 
effective power is steam ; but unless this can be used in conjunc- 
tion with other works, as in the case quoted above, the cost is 
too great for such supplies as are here treated of. Wind, how- 
ever, supplies a cheap and, although at times intermittent, a 
fairly effective motive power, costing nothing in the way of 
fuel and little in the way of attention. Small wind-engines, fixed 
either on the top of the highest farm-building or on skeleton 
frames of wood, are coming to be ver^' extensively used for 
pumping, and for working chaff-cutting machines and mills for 
grinding meal. In America they are much more extensively 
used than in England, and a full description of the American 
wind-engines, with illustrations, will be found in the last volume 
of the ' Journal ' at page 67. t In the Colonies, and in India 
also, great numbers are in use for supplying water to the tanks 
at the railway stations. In Australia, where drought prevails 
for many months in the summer, and where manual labour is 
exceedingly expensive, the water used for the vineyards, for 
agricultural purposes, and for the large horse, sheep, and cattle 
* Tomlinson's ' Cyclopjcdia of Arts ami Maniifacturprs.' Virtue and Co., 18CG. 
t ' Journal of tho hoyal Agricultural Society,' Second Series, toI. xxiii., 1877. 
