As it has burst immediately in the line of sight of B, but with the smoke obscured by the figure of the balloon C, it is obvious to B that the explosion has occurred behind the objective, but at what distance he cannot tell. To O1 and O2,however, it is seen to have burst at a considerable distance behind C though to the former it appears to have burst to the left and to the second observer to the right of the target.
Another shell, at "short" range, is now fired, and it bursts at E. The explosion takes place in the line of sight of B, who knows that he has fired short of the balloon because the latter is eclipsed by the smoke. But the two observers see that it is very short, and here again the explosion appears to O1 to have occurred to the right of the target, while to O2 it has evidently burst to the left of the aerostat, as revealed by the relation of the position of the balloon to the bursting of the shell shown in Fig. 3.
A third round is fired, and the shell explodes at F. In this instance the explosion takes place below the balloon. Both the observers and the artillery man concur in their deductions upon the point at which the shell burst. But the shell must explode above the balloon, and accordingly a fourth round is discharged and the shell bursts at G.
This appears to be above the balloon, inasmuch as the lines of sight of the two observers and B converge at this point. But whether the explosion occurs immediately above the vessel as is desired, it is impossible to say definitely, because it may explode too far behind to be effective. Consequently, if this shell should prove abortive, the practice is to decrease the range gradually with each succeeding round until the explosion occurs at the critical point, when, of course, the balloon is destroyed. An interesting idea of the difficulty of picking up the range of a captive balloon may be gathered from the fact that some ten minutes are required to complete the operation.
But success is due more to luck than judgment. In the foregoing explanation it is premised that the aerial vessel remains stationary, which is an ex tremely unlikely contingency. While those upon the ground are striving to pick up the range, the observer is equally active in his efforts to baffle his opponents. The observer follows each successive, round with keen interest, and when the shells appear to be bursting at uncomfortably close quarters naturally he intimates to his colleagues below that he desires his position to be changed, either by ascending to a higher point or descending. In fact, he may be content to come to the ground. Nor must the fact be overlooked that while the enemy is trying to place the observer hors de combat, he is revealing the position of his artillery, and the observer is equally industrious in picking up the range of the hostile guns for the benefit of his friends below.
When the captive balloon is aloft in a wind the chances of the enemy picking up the range thereof are extremely slender, as it is continually swinging to and fro. While there is always the possibility of a shell bursting at such a lucky moment as to demolish the aerial target, it is generally conceded to be impossible to induce a shell to burst within 100 yards of a balloon, no matter how skilfully the hostile battery may be operated.
The value of the captive balloon has been demonstrated very strikingly throughout the attack upon the entrenched German positions in Flanders. Owing to the undulating character of the dunes the "spotters" upon the British monitors and battle ships are unable to obtain a sweeping view of the country. Accordingly captive balloons are sent aloft in some cases from the deck of the monitors, and in others from a suitable point upon the beach itself. The aerial observer from his point of vantage is able to pick up the positions of the German forces and artillery with ease and to communicate the data thus gained to the British vessels, although subjected to heavy and continuous hostile fire.
The difficulty of hitting a captive balloon has been graphically emphasised, inasmuch as the German artillerists have failed to bring down a solitary balloon. On the other hand the observer in the air is able to signal the results of each salvo fired from the British battleships as they manoeuvre at full speed up and down the coastline, while he keeps the fire of the monitors concentrated upon the German positions until the latter have been rendered untenable or demolished. The accuracy of the British gun-fire has astonished even the Germans, but it has been directly attributable to the rangefinder perched in the car of the captive balloon and his rapid transmission of information to the vessels below.
The enthusiastic supporters of aerial navigation maintained that the dirigible and the aeroplane would supersede the captive balloon completely. But as a matter of fact the present conflict has established the value of this factor more firmly than ever.
There is not the slightest possibility that the captive balloon sections of the belligerents will be disbanded, especially those which have the fruits of experience to guide them. The airship and the aeroplane have accomplished wonders, but despite their achievements the captive balloon has fully substantiated its value as a military unit in its particular field of operations.
