It is noteworthy that although the German airships were expected to act as scouts in the North Sea they do not appear to have accomplished anything in this direction.  Possibly this has been due to the fear of attack by our men-of-war or aircraft if the movements were made in daytime, when alone they would be useful for this purpose.  What happened during the Christmas Day affair, when, as the official report said, “a novel combat” ensued between the 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 can hope to have a repetition of