There were, however, plenty of evidences that the Germans were rushing up thousands of troops in order to deal with the supposed landing in force. Train after train made towards the town, crammed with soldiers.
The sea-planes let the trains pass unhindered. It was not their purpose to stop Germans from pouring into Zeebrugge. Once the troops were there, then would be the time to cut their lines of communication.
Again the monitors opened fire. Their reception was hotter than it had been in the neighbourhood of Ostend, for, in spite of frequent and destructive molestation, the Germans had succeeded in throwing up numerous heavily armed and cleverly concealed batteries.
At almost extreme range the British ships maintained a rapid high-angle fire. In a few minutes fires had broken out in several places. Fifteen-hundred-pound shells dropped in the canal basin, blowing to atoms several submarines that were in the process of fitting out. The harbour works were swept by the huge projectiles. The long curved breakwater suffered heavily. Huge gaps appeared in the solid masonry. Everything lying afloat in the enclosed water was either set on fire or sunk. In an hour the havoc wrought at Zeebrugge had wiped out the work of months.
Ross had little time to notice the work of destruction. His particular business was to observe the fire directed upon a large redoubt to the north-east of the town. The first shell from the monitor fell short, blowing an enormous crater in the grass-grown dunes. The second fell beyond, completely demolishing a house. The third dropped fairly in the centre of the redoubt, causing a terrific explosion that was not due solely to the lyddite bursting-charge. The magazine had exploded.
Skywards rushed an enormous cloud of black and yellow smoke. Caught by the blast of the violently displaced air the sea-plane rocked, then began dropping like a stone.
For the moment Ross imagined that the end had come. He was no longer afraid. A sensation of intense curiosity as to what the machine and its occupants would look like seemed to obsess his mind.
Then, with a jerk that reminded the midshipman of the sudden starting of a lift, the sea-plane "flattened out" and began to climb out of the enveloping cloud of smoke.
The Flight-Sub turned his head and grinned broadly. His manner could not do otherwise than inspire confidence. Although not a pilot, he was master of the frail machine. Side-slips and nose-dives troubled him but little, provided he was flying at a safe altitude.
"A jolly good wipe-out!" he exclaimed. "There won't be many Bosches left within half a mile of that battery, I'm thinking. Now watch when the next shot lands: that will give you the objective."
A sharp buzzing in the receiver attached to Ross's flying helmet announced that the monitor was "calling up" her observer. Quickly the lad seized the pencil, and gave the signal that he was ready to take down the message.
The Morse signal, when translated into writing, was as follows:—
"Register Position 47."
"Good!" exclaimed the Plight-Sub when Ross had telephoned him the message. He consulted his map, which was similar to the one at the observer's disposal "Position 47: that's a railway junction."
In the course of their work of fortifying Zeebrugge, the Huns had constructed a double-track railway, passing within a few yards of the Dutch frontier for several miles before heading straight for the new submarine base. Two miles from Zeebrugge the line joined the existing railway, the junction being recorded on British airmen's maps as Position 47.
The time was now ripe for the monitor which had successfully demolished the redoubt to attempt a similar exploit, namely, to destroy the junction.
The sea-plane's appearance was the signal for a furious fire from the numerous anti-aircraft guns mounted in the vicinity of the station.
At six thousand feet the risk of being hit was small, while the height did not prevent the observer making a fairly accurate register of the hits.
It was a very long range, but the monitor's 14-inch guns did excellent work. Seven shells sufficed to reduce the station to a heap of ruins and blow whole sections of the line to atoms.
Again came a wireless order:
"Sea-plane to proceed to Zwilhuit. Attempt destruction of bridge across canal."
Once more the Flight-Sub smiled. This was work that suited him immensely. For the nonce "spotting" was finished with. The sea-plane had to drop her cargo of bombs upon an important strategic position.
"All right!" exclaimed the Flying officer. "Keep a cool head. When I give the word, press that pedal under your right foot. Bend down and you'll find a safety pin just above the floor. Remove it, but be jolly careful not to touch the pedal until I give the word."
Underneath the fuselage were six bombs hanging from an inclined steel rod. These were released by means of a rachet operated by the pedal to which the Flight-Sub had alluded. To prevent a premature release the pedal was "locked" by a safety device. When this was removed, each depression of the pedal would result in the liberation of a potent missile of destruction.
The sea-plane was not alone on her errand. In her wake flew two more, for the actual bombardment had now ceased, and the air-craft were at liberty to engage upon a raid several miles inland.
The Huns had not constructed their strategic railway close to the Dutch frontier without a cunning reason. Extreme care had to be exercised by British airmen, since it was an easy matter for a bomb to drop across the border. Nothing would please the Germans better, for at once there would be a case of violation of Dutch territory. On the other hand, the Huns had no scruple in mounting a battery of anti-aircraft guns, training them in such a manner that the earthward flight of spent shrapnel would assuredly fall upon the Dutch village of Venterloos, which was separated from Zwilhuit by a distance of less than four hundred yards.
In twenty minutes the sea-plane's objective came in sight: a broad line of railway crossing a canal by means of a steel bridge. It was evident that the Germans meant this base to be a permanent one, for the bridge was of massive construction, strong enough to bear the transport of the heavy 42-centimetre guns, and yet sufficiently high above the waterway to admit the passage of large lighters with towering deck-cargoes.
"Stand by!" cautioned the Flight-Sub. "Keep cool. Do as well as you have already done, and everything will go like greased lightning."
Volplaning at an acute angle, the sea-plane swooped down upon her quarry. Shrapnel shells burst over, in front, behind, and underneath her. It seemed impossible that such a frail object could escape destruction.
At five hundred feet the Flight-Sub checked her downward course.
"Now!" he ordered. "And again!"
Two puffs of white smoke marked the points of explosion of the powerful bombs. One had fallen fifty yards short of the bridge; the other had burst almost at the junction of the railway lines.
Round spun the sea-plane. As she turned Ross could discern the second of the aerial raiders gliding down, while the third was still at a great altitude. Before the one in which Ross was flying could again soar over its target the second sea-plane had dropped three of her missiles. All fell close to the bridge. The work of demolition was accomplished, for when the smoke and dust cleared away the substantial fabric had been precipitated, a mass of twisted steel, into the canal.
"THE WORK OF DEMOLITION WAS ACCOMPLISHED"
"Two more on the station and then we've finished," exclaimed the Flight-Sub. "Ready?"
"Ay, ay!" replied Ross.
He turned his head to watch the progress of the other sea-planes. One was still maintaining a terrific altitude, and showed no signs of making a volplane.