Since those times, the aeroplane has placed in the hands of military commanders a powerful weapon, not only of espionage or scouting, but also of communicating information, and probably not even Bismarck, were he still alive, could contend that the use of aeroplanes could be regarded as bringing the airman within the laws of espionage. And there is no difference in principle between the aeroplane and the balloon. Obviously, there can be none of the concealment which is necessary to establish spying.

The invention of wireless telegraphy brought about a curious problem in espionage during the Russo-Japanese War. A steamer, fitted with a wireless installation, followed the movements of the rival fleets in the interests of one of the London papers. She was boarded by a Russian cruiser, and, as result, the Russian Government informed the neutral Powers that should any neutral vessel be found within the Russian maritime zone, having on board correspondents with apparatus of this kind—which, obviously, was not foreseen in the then existing Conventions—used for the purpose of transmitting information to the enemy, the correspondents would be treated as spies, and the vessels made prizes of war. That position is now untenable.

Owing to the improvements made in wireless telegraphy, a very similar situation might arise in a land war. It is possible, to-day, to carry in an ordinary motor-car a wireless outfit capable of sending messages a very considerable distance; indeed, there is good reason for believing that such an apparatus is actually being used by German agents for transmitting information from the east and north-east districts of England, to enemy submarines lurking in the North Sea. A rigorous search has been made for this mysterious car, which has been reported in various districts. Naturally, when the apparatus is not in use it is concealed within the body of the car, which would then become, apparently, an ordinary touring vehicle, with nothing to distinguish it from hundreds of others passing freely along the roads.

In this case there would be little doubt about the fate of the occupants of the car if they were caught. They would not be "spies" in the strict sense of the word, as their offence was not committed within the zone of the operations, but they would be guilty of "war treason," and liable to the death penalty.

This is a very real danger, and the offence is one that it would be extremely difficult to detect. The popular idea of a wireless plant, gained no doubt from the enormous "aerials" of the high-power stations sending messages thousands of miles, is that wireless telegraphy is something that cannot be carried on without employing huge plant that it would be impossible to conceal.

Now I can claim to know something of wireless telegraphy—I have experimented for some years—and I can say, at once, that this is an exceedingly dangerous fallacy. In recent years very great improvements have been made in both transmitters and receivers, and to-day it is quite possible to establish in almost any house, a small, but powerful wireless plant, which would be utterly invisible from outside, but quite capable of sending messages from any spot near the coast to enemy vessels, such as submarines, lying a few miles away.

Of secret installations there are, no doubt, to-day, many in various parts of the country. Several stations have, indeed, been discovered. The reason aliens were not allowed to possess a telephone was regarded as curious by some people. But it was because telephone-wires, when properly insulated and arranged, make quite a good "aerial." Further, in any barn or long attic, aerial wires can be strung across, and give excellent results. The spy does not need spidery wires upon masts high above his house-top, or in his garden. If his instruments are sufficiently delicate, and are connected with the underground gas-pipe, or even to an ordinary wire-mattress, he will be able to receive messages from any of the high-power stations within a radius of, say, five hundred miles, while from a wire strung inside a disused factory-chimney, and thereby hidden, a wireless message can be despatched a couple of hundred miles. Therefore the peril of all this will at once be realised, for any spy who knows sufficient to fit up a wireless station inside his own house, and is acquainted with the latest developments of the science, need not use lamp-signalling at night, or pigeons, or any other antiquated modes of communication. Indeed, he can flash at night a code-message direct to Norddeich or any other place on the German coast, and receive back his answer in a few moments, no one being able to detect, until after long search and inquiry, whence the mysterious buzz has emanated.

It ought to be said, however, that it is problematical how long such a fixed station, established say in Yorkshire, could be worked without detection, because its messages must—sooner or later—be picked up by some of our own Post Office or naval operators. The messages would be in cipher, of course, but the important thing would be to know that such a plant was being used. An expert wireless-operator, with a newly-invented instrument called a "direction-finder," can make a very good guess at the distance of the point of origin of any message he receives, and once the proper authorities were on the track of a secret wireless station, the work of hunting it down would be only a matter of time and trouble. Such a case was reported a few weeks ago from the Pacific coast, where a wireless station established in the centre of a remote district was giving the Germans valuable help. It was tracked down and located, and it is said that a similar station was found in the centre of Rome, and others in Paris and Antwerp. We might be equally successful here, but, in the meantime, it is more than likely that a good deal of damage might have been done.

The case of a wireless installation used for a motor-car, however, presents much more difficulty of detection. We might know perfectly well that it was being used, and yet be unable to locate it on account of its mobility. It is practically certain that it would never be used twice from the same spot; indeed, it might operate along a line running a couple of hundred miles north and south, and still convey its messages to the enemy vessels. In such a case as this, we can only rely upon vigilance and good luck to turn the trick in our favour.

In my view, the Admiralty took an extremely unwise step when, at the beginning of the war, they closed all the private wireless stations in England. There are a great many of these stations—far more than the general public realises—and the majority of them were being worked by men whose loyalty and discretion stood absolutely above suspicion. These installations—free from the heavy load of business thrown upon the Government coast stations—are quite capable of doing excellent work in constantly "listening" for illicit stations which might be in the hands of German spies for the purpose of giving information respecting our naval movements. The value of these small stations as a means of detecting hostile messages has been entirely under-estimated by the Admiralty, who seem to consider the risk of Englishmen being either traitors or fools more than outweighs the possibility of detecting secret wireless in the hands of our enemies.