other is its speed. If the speed is slow it will
quickly wend its way to the earth in a gradual
curve. This curved line is called its trajectory.
If it is not very large diametrically, in proportion
to its weight, it will also make a gradual curve in
descending, without "skimming" up and down
in its flight.

SHAPE AND SPEED.--It has been observed, also,
that a round ball, or an object not flattened out,
will make a regular curved path, whatever the
speed may be.

It may be assumed, therefore, that the shape
alone does not account for this sinuous motion;
but that speed is the element which accounts for
it. Such being the case it may be well to inquire
into the peculiar action which causes a skipper
to dart up and down, and why the path thus
formed grows more and more accentuated as the
speed increases.

As will be more fully described in a later chapter,
the impact of air against a moving body does
not increase in proportion to its speed, but in the
ratio of the square of the speed.

WHAT SQUARE OF THE SPEED MEANS.--In mathematics
a figure is squared when it is multiplied
by itself. Thus, 4 X 4= 16; 5 X 5 = 25; and so