lines of the aeroplane. It must descend to the level where a
clear view of the ground may be obtained, and in the interests of safety
it has to keep on the move. To attempt to hover within 4,000 feet of
the ground is to court certain disaster, inasmuch as the vessel offers
a magnificent and steady target which the average gunner, equipped with
the latest sighting devices and the most recent types of guns, scarcely
could fail to hit.

But the airman in the aeroplane is able to descend to a comparatively
low level in safety. The speed and mobility of his machine constitute
his protection. He can vary his altitude, perhaps only thirty or forty
feet, with ease and rapidity, and this erratic movement is more than
sufficient to perplex the marksmen below, although the airman is
endangered if a rafale is fired in such a manner as to cover a wide
zone.

Although the aeroplane may travel rapidly it is not too fleet for a keen
observer who is skilled in his peculiar task. He may only gather a
rough idea of the disposition of troops, their movements, the lines
of communication, and other details which are indispensable to his
commander, but in the main the intelligence will be fairly accurate.
Undulating flight enables him to determine speedily the altitude at
which he is able to obtain the clearest views of the country beneath.
Moreover, owing to his speed he is able to complete his task in far less
time than his colleague operating in the dirigible, the result being
that the information placed at the disposal of his superior officers is
more to the moment, and accordingly of greater value.

Reconnoitring by aeroplane may be divided into two broad categories,
which, though correlated to a certain degree, are distinctive, because
each constitutes a specific phase in military operations. They are known
respectively as "tactical" and "strategical" movements. The first is
somewhat limited in its scope as compared with the latter, and
has invariably to be carried out rapidly, whereas the strategical
reconnaissance may occupy several hours.

The tactical reconnaissance concerns the corps or divisional commander
to which the warplane is attached, and consequently its task is confined
to the observation of the line immediately facing the particular corps
or division. The aviator does not necessarily penetrate beyond the lines
of the enemy, but, as a rule limits his flight to some distance from
his outermost defences. The airman must