52 
On Water Supplies suited to 
second, or 75 per minute. In consequence of the water issuing' 
all round the ring, sufficient water-way can be obtained with 
wheels of small diameter, and hence the speed of revolution in 
this class of motors is very high. Pumps may be arranged, so 
as to be driven direct from the spindle by cranks attached to it,, 
or the speed, if very high, may be reduced to a moderate amount 
by suitable gearing. 
The dimensions and form of turbines depend so much upon 
the particular conditions under which they have to work, that 
it is impossible to give any general idea of cost. 
Turbines occupying but a small compass, can frequently be- 
arranged in vaults by the side of the stream, and so kept from 
frost and from disfiguring the landscape. They require careful' 
attention in oiling, cleaning, and periodic adjustment, and 
cannot, on that account, be recommended where more simple 
motors can be used. 
When the fall available is not less than 4 feet and the lift not 
more than fifteen times the fall, hydraulic rams are the best and' 
cheapest water-raising engines to employ. 
Fig. 6. — Section of Hydraulic-Sam. 
The ram consists of an inclined injection-pipe, A (Fig-. 6^ 
which is inserted by the permission of the Royal Institution), 
which leads the water from a reservoir into a chamber B, which- 
terminates in a valve C, opening inwards. Branching up from 
the chamber is a passage leading to a valve D, opening out- 
