tion for these influences can be made the ship will wander
considerably from its course. The airman is placed in a worse position.
He has no means of determining the direction and velocity of the
currents prevailing in the atmosphere, and his compass cannot give him
any help in this connection, because it merely indicates direction.

Unless the airman has some means of determining his position, such as
landmarks, he fails to realise the fact that he is drifting, or, even
if he becomes aware of this fact, it is by no means a simple
straightforward matter for him to make adequate allowance for the
factor. Side-drift is the aviator's greatest enemy. It cannot be
determined with any degree of accuracy. If the compass were an
infallible guide the airman would be able to complete a given journey
in dense fog just as easily as in clear weather. It is the action of the
cross currents and the unconscious drift which render movement in the
air during fog as impracticable with safety as manoeuvring through the
water under similar conditions. More than one bold and skilful aviator
has essayed the crossing of the English Channel and, being overtaken by
fog, has failed to make the opposite coast. His compass has given him
the proper direction, but the side-drift has proved his undoing, with
the result that he has missed his objective.

The fickle character of the winds over the water, especially over such
expanses as the North Sea, constitutes another and seriously adverse
factor. Storms, squalls, gales, and, in winter, blizzards, spring up
with magical suddenness, and are so severe that no aircraft could hope
to live in them. But such visitations are more to be dreaded by the
lighter-than-air than by the heavier-than-air machines. The former
offers a considerable area of resistance to the tempest and is caught up
by the whirlwind before the pilot fully grasps the significant chance
of the natural phenomenon. Once a dirigible is swept out of the hands of
its pilot its doom is sealed.

On the other hand, the speed attainable by the aeroplane constitutes its
safety. It can run before the wind, and meantime can climb steadily and
rapidly to a higher altitude, until at last it enters a contrary wind or
even a tolerably quiescent atmosphere. Even if it encounters the tempest
head on there is no immediate danger if the aviator keep cool. This
fact has been established times out of number and the airman has been
sufficiently skilful and q