that angle with a heavy
wind blowing against it, and attach two pairs of
scales to the plane, both would show the same
pull.

_Fig. 6. Measuring Lift and Drift_

MEASURING LIFT AND DRIFT.--In Fig. 6, A is the
plane, B the horizontal line which attaches the
plane to a scale C, and D the line attaching it to
the scale E. When the wind is of sufficient force
to hold up the plane, the scales will show the same
pull, neglecting, of course, the weight of the
plane itself.

PRESSURE AT DIFFERENT ANGLES.--What every
one wants to know, and a subject on which a
great deal of experiment and time have been expended,
is to determine what the pressures are at
the different angles between the horizontal, and
laws have been formulated which enable the pressures
to be calculated.

DIFFERENCE BETWEEN LIFT AND DRIFT IN MOTION.--The
first observation is directed to the differences
that exist between the lift and drift,
when the plane is placed at an angle of less than
45 degrees. A machine weighing 1000 pounds
has always the same lift. Its mass does not
change. Remember, now, we allude to its mass,
or density.

We are not now referring to weight, because
that must be taken into consideration, in the
problem. As heretofore stated, when an object
moves horizontally, it has less weight than when
at rest. If it had the same weight it would not
move forwardly, but come to rest.

When in motion, therefore, while the lift, so
far as its mass is concerned, does not change, the
drift does decrease, or the forward pull is less
than when at 45 degrees, and the decrease is less
and less until the plane assumes a horizontal position,
where it is absolutely nil, if we do not consider
head resistance.

TABLES OF LIFT AND DRIFT.--All tables of Lift
and Drift consider only the air pressures. They
do not take into account the fact that momentum
takes an important part in the translation of an
object, like a flying machine.

A mass of material, weighing 1000 pounds while
at rest, sets up an enormous energy when moving
through the air at fifty, seventy