across the
Atlantic, and forced to come down to the Irish Sea is one example. The
NC-4, American naval seaplane, had a forced landing at sea, a hundred
miles from Chatham, Massachusetts, on the first leg of the Atlantic
flight from this side. Its engines had been carefully cleaned and
tested, and yet they failed. Harry G. Hawker's engine failed him
half-way from Newfoundland to Ireland and let him down into the sea,
from which he was picked up by the greatest good luck.

That is one of the most exasperating and human things about a
gasolene-engine. It is efficient, but not thoroughly dependable. The
best of them are liable to break down at the most needed moment, due
to a hundred causes outside of the control of a mechanic or pilot.
Care and rigid inspection will reduce the possibilities, but engine
failure cannot yet be eliminated.

That is one of the principal reasons why the roofs of buildings around
big cities are so dangerous. The sides of a building drop away from
the roof. An error in judgment and the machine is over the edge.

It is even more dangerous to take-off. An airplane motor is ten times
as likely to develop a weakness while it is cold. A motor starting a
flight is never well warmed up, and fifty feet from the edge of the
roof it may give out, with awful consequences. As a practicable thing,
roofs are at present impossible. There is not a flying-officer in the
world who will not agree.

An interesting series of experiments has been carried out in England
on what has been known as the helicopter machine. This machine is not
dependent upon speed to fly, but merely on engine power applied
through a propeller of great pitch. The idea is not new, but is along
the lines specified by Orville Wright when he said that a kitchen
table could fly if it had a good enough engine.

The effort is being made to make a machine which can hover, can hold
itself in the air by brute force of its propeller blades beating the
air. The thing sounds impossible to adapt, say some aeronautical
engineers. Those who have seen the experiments, however, express great
optimism.

A machine of this sort would land and take-off in a very small space,
and might be adapted to use around cities. It might even make flying
over cities safe but for the human equation of the engine again. This
machine is dependent on engine power. Apparently there would be two
engines, or two driving mechanisms, one operating the lifting
propeller and th