Such
parachutes are found to keep their form when stretched by the water better
than a surface originally spherical, although the latter would be
theoretically more correct. The motion of the drum is transmitted by spur,
gear, or otherwise as may be required, to give the requisite speed.

It will be seen that the advantages of the system are as follows: First,
the facility it offers for obtaining a large working area, which may be
increased or diminished at will, according to the requirements of the
moment, by lengthening or shortening the rope. Secondly, the ease with
which it is erected and set to work. Thirdly, the small part of the river
section which it occupies, so as to present no obstacle to navigation.
Fourthly, the ease with which it can be mounted on a barge of any kind,
and carried wherever it may be needed. Fifthly, it is not stopped, like
all other hydraulic motors, by the appearance of ice--it has, in fact,
already been worked under ice in the Neva. At the same time, winds and
waves have no influence upon it.

The principle of the apparatus is not altogether new. In 1872 there was
tried on the Ohio River an arrangement termed the Brooks motor. It was
composed of two drums, placed horizontally and parallel to each other.
Round these there passed endless chains at equal spaces apart on the
length of the drums, and to these chains were fixed wooden blades or arms
of a curved form, and so jointed to the frames that they opened when
moving in one direction, and closed down on the chain when moving in the
other. In this machine the weight of the chains was a serious obstacle to
obtaining any large amount of power. The whole apparatus was mounted on a
heavy wooden scaffold, which proved an impediment to the flow of the
river. Again, the resistance due to the surface of the returning blades
and to their stiffness was found to be far from insignificant.

In the present system Mr. Jagn has found, after many experiments, that the
best effect was obtained when the parachutes were spaced apart at twice
their diameter, and when the rope made an angle of 8 degrees to 10 degrees
with the current. It is found that when open and in motion the parachutes
never touch the bottom. This was the case with a rope containing 180
parachutes of 4 feet diameter, and working in a depth of only 6 feet. This
is easily explained by the fact that the velocity of a current always
diminishes as it approaches the bottom. Hence the pressure