The mobile quick-firers made no attempt to get into action until the cars were almost abreast of the spot where Tressidar and his companions were. Had they done so, the chances were that the falling shrapnel bullets would do considerable damage to the lightly built roofs of the munition works.
Suddenly six anti-aircraft guns opened fire simultaneously. The air was torn with the shriek of the high-velocity projectiles and the sharp reports of the weapons. The explosion of the shells threw a blaze of light upon the silvery envelope of the gigantic night-raider. It seemed as if it would be impossible for her to escape the wide effect of the bursting projectiles.
Doris clasped her hands and waited, fully expecting that the huge floating fabric would either burst into flame or drop, a crumpled mass of metal, upon the ground.
The Zeppelin lurched. Her bow part tilted sharply downwards. Her searchlights were switched off. At the same time the British searchlights threw their concentrated beams upon their quarry. Smoke was pouring from the hard-pressed airship, until her outlines were hidden by the pall of vapour.
Then, to an accompaniment of a perfect tornado of exploding bombs for the airship had hurriedly thrown out her remaining supply of missiles, the Zeppelin shot vertically upwards with almost incredible velocity. Growing smaller and smaller to the sightseers, it gradually grew more and more indistinct, until the searchlight men were unable to locate its position. The last seen of her was that she was travelling slowly in a south-easterly direction.
"Hulloa! What the deuce have we got here?" inquired a deep, hearty voice. "Car with a blaze of red lights, by Jove!"
Towards the Mercédès car strode a burly, great-coated figure in the uniform of a lieutenant in the R.N. Air Service. Following him were seven or eight men from the crews of the motor batteries.
"You have here a car belonging to a couple of German spies," said Tressidar, advancing to meet the lieutenant.
"Nothing like being candid about the business," rejoined the latter drily. "And who might you be?"
The sub. announced his name and rank.