on the lower
part of the parachute will be less than that on the upper part; but the
former pressure tends to draw the parachute downward, while the latter
tends to raise it to the top of the water. Thus, the latter being the
larger, the parachute will always have a tendency to rise. In fact, it is
necessary to sink the return pulley sufficiently deep to make sure that
the parachutes will not emerge from the surface. For the same reason no
intermediate supports are needed over the driving span; if any are needed
it is for the return span, on which the parachutes are closed. Of course,
if metal were used instead of hemp, the case would be entirely different,
and intermediate supports would have to be used for anything but very
moderate lengths.

In practice, Mr. Jagn has employed two ropes wound upon the same pair of
drums, which are mounted upon a pontoon. The ropes are spread out from
each other, as in Fig. 1, making an angle of about 10 degrees. The low
specific gravity of the system enables ropes to be employed of as great a
length as 450 yards, each of them carrying 350 parachutes of 17.2 square
feet area. As half of these are in action at the same time, the total
working area for the two cables is 5,860 square feet. This immense area
furnishes a considerable amount of power even in a river of feeble
current. Comparing this with a floating water wheel of the type sometimes
employed, and supposing this to have only 172 square feet of working area,
such a wheel must have a length of 46 feet, a diameter of 23 feet, and
seventy-two floats, each 21/2 feet wide. The enormous dimensions thus
required for a comparatively small working area point sufficiently clearly
to the advantage which remains on the side of the parachute motor.

The general arrangement of the system is shown in the engraving. Behind
the return pulleys, D D, are attached cords, A A, with some parachutes
strung upon them. These present their openings to the current and preserve
the tension of the connecting ropes. At the further end of each cord is a
board, B, which is kept in a vertical plane, but lying at a slight angle
to the direction of the current; and this acts to keep the two moving
ropes apart from each other. The two return pulleys are, however,
connected by a line, E, which can be shortened or lengthened from the
pontoon, and in this way the angle of inclination between the two ropes
can be varied if required. A grooved pulley presses upon the