There is one field in which the airman has achieved distinctive triumphs. This is in the guidance of artillery fire. The modern battle depends first and foremost upon the fierce effec tiveness of big-gun assault, but to ensure this reliable direction is imperative. No force has proved so invaluable for this purpose as the man of-the-air, and consequently this is the province in which he has been exceptionally and successfully active.

It will be recalled that in the Japanese investiture of Port Arthur during the Russo-Japanese war, thousands of lives were expended upon the retention and assault of 203 Metre Hill. It was the most blood-stained spot upon the whole of the Eastern Asiatic battlefield. General Nogi threw thousands after thousands of his warriors against this rampart while the Russians defended it no less resolutely. It was captured and re-captured; in fact, the fighting round this eminence was so intense that it appeared to the outsider to be more important to both sides than even Port Arthur itself.

Yet if General Nogi had been in the possession of a single aeroplane or dirigible it is safe to assert that scarcely one hundred Japanese or Russian soldiers would have met their fate upon this hill. Its value to the Japanese lay in one sole factor. The Japanese heavy guns shelling the harbour and the fleet it contained were posted upon the further side of this eminence and the fire of these weapons was more or less haphazard. No means of directing the artillery upon the vital points were available; 203 Metre Hill interrupted the line of sight. The Japanese thereupon resolved to capture the hill, while the Russians, equally appreciative of the obstruction it offered to their enemy, as valiantly strove to hold it. Once the hill was captured and the fire of the Japanese guns could be directed, the fate of the fortress was sealed.

Similar conditions have prevailed during the present campaign, especially in the western theatre of war, where the ruggedness of the country has tended to render artillery fire ineffective and expensive unless efficiently controlled. When the German Army attacked the line of the British forces so vehemently and compelled the retreat at Mons, the devastating fire of the enemy's artillery was directed almost exclusively by their airmen, who hovered over the British lines, indicating exactly the point where gun-fire could work the maximum of havoc. The instant concentration of massed artillery fire upon the indicated positions speedily rendered one position after another untenable.

The Germans maintained the upper hand until at last the aerial forces of the British Expeditionary Army came into action. These airmen attacked the Teuton aerial craft without the slightest hesitation, and in a short while rendered cloudland absolutely unhealthy. The sequel was interesting. As if suddenly blinded, the German artillery fire immediately deteriorated. On the other hand, the British artillery, now having the benefit of aerial guidance, was able to repay the German onslaughts with interest, and speedily compelled that elaborate digging-in of the infantry lines which has now become so characteristic of the opposing forces.

So far as the British lines are concerned the men in the trenches keep a sharp look-out for hostile aeroplanes. The moment one is observed to be advancing, all the men seclude themselves and maintain their concealment. To do otherwise is to court a raking artillery outburst. The German aeroplane, detecting the tendency of the trenches describes in the air the location of the vulnerable spot and the precise disposition by flying immediately above the line. Twice the manoeuvre is repeated, the second movement evidently being in the character of a check upon the first observation, and in accordance with instructions, whereupon the Tommies, to quote their own words, "know they are in for it!" Ere the aeroplane has completed the second manoeuvre the German guns ring out.

The facility with which artillery fire can be concentrated through the medium of the aeroplane is amazing. In one instance, according to the story related to me by an officer, "a number of our men were resting in an open field immediately behind the second line of trenches, being in fact the reserves intended for the relief of the front lines during the following night. An aeroplane hove in sight. The men dropped their kits and got under cover in an adjacent wood. The aeroplane was flying at a great height and evidently laboured under the impression that the kits were men. Twice it flew over the field in the usual manner, and then the storm of shrapnel, 'Jack Johnsons' and other tokens from the Kaiser rained upon the confined space. A round four hundred shells were dropped into that field in the short period of ten minutes, and the range was so accurate that no single shell fell outside the space. Had the men not hurried to cover not one would have been left alive to tell the tale, because every square foot of the land was searched through and through. We laughed at the short-sightedness of the airman who had contributed to such a waste of valuable shot and shell, but at the same time appreciated the narrowness of our own escape."

The above instance is by no means isolated. It has happened time after time. The slightest sign of activity in a trench when a "Taube" is overhead suffices to cause the trench to be blown to fragments, and time after time the British soldiers have had to lie prone in their trenches and suffer partial burial as an alternative to being riddled by shrapnel.

The method of ascertaining the range of the target from the indications given by the aeroplane are of the simplest character. The German method is for the aerial craft to fly over the position, and when in vertical line therewith to discharge a handful of tinsel, which, in falling, glitters in the sunlight, or to launch a smoking missile which answers the same purpose as a projectile provided with a tracer. This smoke-ball being dropped over the position leaves a trail of black or whitish smoke according to the climatic conditions which prevail, the object being to enable the signal to be picked up with the greatest facility. The height at which the aerial craft is flying being known, a little triangulation upon the part of the observer at the firing point enables him to calculate the range and to have the guns laid accordingly.

When the aerial craft has been entrusted with the especial duty of directing artillery-fire, a system of communication between the aerial observer and the officer in charge of the artillery is established, conducted, of course, by code. In the British Army, signalling is both visual and audible. In daylight visual signalling is carried out by means of coloured flags or streamers and smoke-signals, while audible communication is effected by means of a powerful horn working upon the siren principle and similar to those used by automobiles. Both flags and sound-signals, however, are restricted owing to the comparatively short distances over which they can be read with any degree of accuracy. The smoke-signal therefore appears to be the most satisfactory and reliable, as the German airmen have proved conclusively, for the simple reason that the trail of smoke may be picked up with comparative ease, even at a distance, by means of field glasses. The tinsel too, is readily distinguishable, particularly in bright weather, for the glittering surface, catching the sun-light, acts some what in the manner of a heliograph.

The progress of the airman is followed by two officers at the base from which he started. One is equipped with the director, while the second takes the range. Directly this has been found as a result of calculation, the guns are laid ready for firing. In those cases where the enemy's artillery is concealed perhaps behind a hill, the airman is of incalculable value, inasmuch as he is able to reveal a position which otherwise would have to be found by considerable haphazard firing, and which, even if followed by a captive balloon anchored above the firing point, might resist correction.

The accuracy of the airman's work in communicating the range has been responsible for the high efficiency of the British and French artillery. The latter, with the 75 millimetre quick-firing gun, is particularly adapted to following up the results of the aeroplane's reconnaissance, especially with the system of rafale fire, because the whole position can be searched through and through within a minute or two. According to information which has been given to me by our artillery officers, the British system also has proved disastrous to the enemy. The practice is to get the range as communicated by the aeroplane, to bring the artillery into position speedily, to discharge salvo after salvo with all speed for a few minutes, and then to wheel the artillery away before any hostile fire can be returned. The celerity with which the British artillery comes into, and goes out of, action has astonished even our own authorities. This mobility is of unique value: it is taking advantage of a somewhat slow-witted enemy with interest. By the time the Germans have opened fire upon the point whence the British guns were discharged, the latter have disappeared and are ready to let fly from another point, some distance away, so that the hostile fire is abortive. Mobility of such a character is decidedly unnerving and baffling even to a quick-witted opponent.

In his search for hostile artillery the airman runs grave risks and displays remarkable resource. It is invariably decided, before he sets out, that he shall always return to a certain altitude to communicate signals. Time after time the guns of the enemy have been concealed so cunningly from aerial observation as to pass unnoticed. This trait became more pronounced as the campaigns of the Aisne progressed. Accordingly the airman adopts a daring procedure. He swoops down over suspicious places, where he thinks guns may be lurking, hoping that the enemy will betray its presence. The ruse is invariably successful. The airman makes a sudden dive towards the earth. The soldiers in hiding below, who have become somewhat demoralised by the accuracy of the British aerial bomb-throwers, have an attack of nerves. They open a spirited fusillade in the hope of bringing the airman to earth. But their very excitement contributes to his safety. The shots are fired without careful aim and expend themselves harmlessly. Sweeping once more upwards, the airman regains the pre-determined level, performs a certain evolution in the air which warns the observer at his base that he has made a discovery, and promptly drops his guiding signal directly over the point from which he has drawn fire.

Operations at night are conducted by means of coloured lights or an electrical searchlight system. In the former instance three lights are generally carried - white, red, and green - each of which has a distinctive meaning. If reliance is placed upon the electric light signalling lamp, then communications are in code. But night operations are somewhat difficult and extremely dangerous, except when the elements are propitious. There is the ground mist which blots everything from sight, rendering reconnaissance purely speculative. But on a clear night the airman is more likely to prove successful. He keeps a vigilant eye upon all ground-lights and by close observation is able to determine their significance. It is for this reason that no lights of any description are permitted in the advance trenches. The striking of a match may easily betray a position to the alert eye above.

So far as the British Army is concerned a complete code is in operation for communicating between aeroplanes and the ground at night. Very's lights are used for this purpose, it being possible to distinguish the respective colours at a distance of six miles and from an altitude of 2,000 feet. The lights are used both by the aeroplane and the battery of artillery.

The code is varied frequently, but the following conveys a rough idea of how communication is carried out by this means under cover of darkness. The aeroplane has located its objective and has returned to the pre-arranged altitude. A red light is thrown by the airman. It indicates that he is directly over the enemy's position. A similarly coloured light is shown by the artillery officer, which intimates to the airman that his signal has been observed and that the range has been taken.

In observing the effects of artillery fire a code of signals is employed between the airman and the artillery officer to indicate whether the shot is "long" or "short," to the right or to the left of the mark, while others intimate whether the fuse is correctly timed or otherwise. It is necessary to change the code fairly frequently, not only lest it should fall into the enemy's hands, but also to baffle the hostile forces; otherwise, after a little experience, the latter would be able to divine the significance of the signals, and, in anticipation of being greeted with a warm fusillade, would complete hurried arrangements to mitigate its effects, if not to vacate the position until the bombardment had ceased.

Sufficient experience has already been gathered, however, to prove the salient fact that the airman is destined to play an important part in the direction and control of artillery-fire. Already he has been responsible for a re-arrangement of strategy and tactics. The man aloft holds such a superior position as to defy subjugation; the alternative is to render his work more difficult, if not absolutely impossible.