tails of a landscape as will prove
conspicuous when seen from above. A river, or an expanse of water, is
clearly seen; so also are railways and main roads; while factory
chimneys, and large buildings which stand alone, may be identified
from a distance when a pilot is in flight. So on an airman's map, made
to stand out by various colourings in a way that catches the eye, are
railways, roads, rivers, lakes and woods, with here and there a
factory chimney or a church, should these be in a position rendering
them visible easily from the air. That such maps should be bold in
their design, and free from a mass of small details, is very necessary
when it is remembered that the aviator, passing through the air at
high speeds, has no time for a leisurely inspection of his map.

With a good map, and aided when necessary by the compass that is
placed in a position so that he can see it readily, a pilot has no
difficulty as a rule, once he has acquired the facility that comes
with practice, in steering accurately from point to point, even when
on a long flight. On a favourable day, when the land below is clearly
visible, he will glance ahead, or to one side, and after observing
some landmark, look on his map to identify the position he has just
seen. Under such conditions steering is easy, and the compass plays a
subsidiary part. But it may happen that, while he is on a long flight
and at a considerable altitude, the earth below may be obscured by
clouds, or a low-lying mist, and all landmarks vanish from his view.
Sometimes too, he may find himself flying through mist and cloud, with
all signs of the earth gone from below. Whereupon, robbed for awhile
of any direct guidance, he must fly by aid of his map and compass,
holding his machine on its compass course, and noting carefully the
needle of his height-recorder, so that he is sure of maintaining
altitude. A risk exists under such conditions, when there is no
visible object by which to judge a course, that an airman may make
leeway, unconsciously, under the pressure of a side-wind; and so he
must be ready to note carefully, immediately that a view of the earth
is vouchsafed him, whether he has actually been making leeway, either
to one hand or the other, even while the bow of his machine has been
held on its compass course. There is a risk also, when a pilot is
flying in fog or at night, that, having no visible horizon from which
to gauge the inclination of his craft, it may ass