ient to raise a
small portion of the discharge to the very moderate height generally
needed to lift it over the banks into the adjoining fields. Why then is it
not employed for the purpose? The answer is obvious, when we consider the
various hydraulic motors at present in use. Of course, motors worked by
water pressure must here be excluded; and we are left with scarcely
anything but the undershot wheel, the turbine, and the screw pump. All
these require expensive buildings and erections to set them to work,
present but a very small fraction of their surface to the water at any one
time, and must be very large and costly if they are to draw even a very
moderate amount of power from such a source. There is no possibility of
adjusting them readily to suit variations in the speed of the current or
in the quantity of water required, nor of moving them from place to place
should this be convenient.

[Illustration: PARACHUTE HYDRAULIC MOTOR.]

The motor of Mr. Jagn is on a totally different principle. Its essential
features consist, as shown, of an endless rope made of hemp or aloe fiber,
which takes a turn or two round a pair of drums mounted on a barge or
pontoon, and then passes down the channel to return over a pulley hung
from a floating punt, at such a depth that the whole of the rope is
immersed in the water. Along this rope are suspended at equal intervals a
number of parachutes made of sail cloth. The rope passes through the
center of each of these, and to it are attached a series of strings, the
other ends of which are connected to the outside edge of the parachute.
Thus they act like the spokes of an umbrella to prevent the parachute from
opening too far under the pressure of the current. The parachutes must be
placed so far apart that the current may act fairly on each, and the sum
of the pressures forms the force which draws the rope through the water.
The moment, however, that any parachute has passed round the return
pulley, the current acts upon it in the opposite direction. It then shuts
up like an umbrella, and assumes a volume so small that its resistance on
the return journey is insignificant. After passing round the drum at the
upper end, it at once opens afresh of its own accord, and once more
becomes part of the moving power of the whole system. The parachutes are
formed by first cutting out a complete circle of cloth, and then taking
from this a sector equal to one-fifth or one-sixth of the total area.