ought, in the near future, to be able to use the
airplane for quick trips to Albany. It would save hours over rail
time, and here the airplane has a wonderful field of usefulness.

Airplanes have made the trip from Washington to New York in very quick
time, only to have to go on to Mineola to land on the airdrome there.
It takes nearly an hour to come in from Mineola, but even at that the
saving of time is still considerable. The speed and efficiency of
airplane travel to and from New York and other cities is materially
affected by the lack of landing-fields close to the business section
of the city.

There must be a large field, broad in every dimension, to permit the
landing and taking-off of airplanes. A machine must get up flying
speed running across the ground before it gets into the air. The
flying speed varies with the type of machine, and it may be estimated
that most machines take-off and land at a speed of from forty-five to
sixty miles an hour. The air must be passing through their planes at
this speed before they will begin to fly, and it takes a little run to
get up flying speed. Similarly, when an airplane lands, it must lose
its flying speed gradually. It may glide to within a few feet of the
ground, and then "flatten out" just off the ground and run along until
it loses its speed, the air no longer passes over its planes fast
enough to support it, and it drops to the ground.

Such are the limitations which the necessity for speed in airplane
flight imposes. Compare the paper dart flying through the air. As long
as it moves quickly it will fly. Or a kite, that will fly when the
wind is strong enough. The airplane creates its own wind to support
itself.

There are four forces acting on an airplane in flight, and they must
be properly overcome and balanced. There is lift, the upward force
exerted on the planes by the passage of air over their surfaces; and
drift, the resistance to the passing of an airplane, the retarding
force acting opposite to the direction of motion. Then thrust, the
forward effort of a machine exerted by a propeller pushing or pulling.
And finally gravity.

The primary conditions of flight are that lift made by the planes
shall be equal to the force of gravity, and that the forward thrust
must be equal to the drift. At that point a machine will sustain
flight--a fairly simple thing on paper. But the times that machines
have stalled in the air, with their motors full on because t