most modern cruisers on the one hand
and the enemy's aircraft and submarines on the other, would not tend to
lessen this apprehension. On the other hand, the greater stability of
the atmosphere at night makes navigation after dark easier, and I
believe that it has been usual in all countries for airships to make
their trial trips at night.

[Illustration: Radius of Action of a Modern Zeppelin

The above outline map, which we reproduce from "The Naval Annual," shows
in the dotted circle the comparative radius of action of a modern
Zeppelin at half-power--about 36 knots speed--with other types of air
machines, assuming her to be based on Cologne. It is estimated that
aircraft of this type, with a displacement of about 22 tons, could run
for 60 hours at half-speed, and cover a distance equivalent to about
2160 sea miles. This would represent the double voyage, out and home,
from Cologne well to the north of the British Isles, to Petrograd, to
Athens, or to Lisbon. The inner circle shows the radius of action of a
Parseval airship at half-power--about 30 knots--based on Farnborough,
and the small inner circle represents the radius of action of a
hydro-aeroplane based on the Medway.]

It is customary also for the airships to carry, in addition to
explosive and incendiary bombs, others which on being dropped throw out
a light and thereby help to indicate to the vessel above the object
which it is desired to aim at. Probably some of the bombs which were
thrown in Norfolk were of this character. It is understood that all idea
of carrying an armament on top of the Zeppelins has now been abandoned,
and it is obvious that if searchlight equipment or guns of any sort were
carried the useful weight for bombs would have to be reduced unless the
range of action was diminished. It will have been noticed that the
Zeppelins which came on Tuesday appear to have been anxious to get back
before daylight, which looks as if they expected to be attacked if they
were seen, as it is fairly certain they would have been.

Assuming the raid of Tuesday to have been in the nature of a trial trip,
it is rather curious that it was not made before. Apparently the
Zeppelins can only trust themselves to make a raid of this description
in very favorable circumstances. Strong winds, heavy rain, or even a
damp atmosphere are all hindrances to be considered. That there will be
more raids is fairly certain, but there cannot be many nights when the
Germans c