on, so that 16 is the square of 4, and 25 the square
of 5. It has been found that a wind moving at the
speed of 20 miles an hour has a striking or pushing
force of 2 pounds on every square foot of surface.

If the wind travels twice as fast, or 40 miles
an hour, the pushing force is not 4 pounds, but
8 pounds. If the speed is 60 miles an hour the
pushing force increases to 18 pounds.

ACTION OF A SKIPPER.--When the skipper leaves
the hands of the thrower it goes through the air
in such a way that its fiat surface is absolutely
on a line with the direction in which it is projected.

At first it moves through the air solely by force
of the power which impels it, and does not in any
way depend on the air to hold it up. See Fig.
1, in which A represents the line of projection,
and B the disk in its flight.

_Fig. 11. A Skipper in Flight._

After it has traveled a certain distance, and
the force decreases, it begins to descend, thus describing
the line C, Fig. 1, the disk B, in this case
descending, without changing its position, which
might be described by saying that it merely settles
down to the earth without changing its plane.