The seaplane had barely risen a thousand feet, when with a shrill scream a heavy shell hurtled through the air from one of the invisible warships. From a distance of twelve thousand yards the 9.2-inch missile struck its objective with a precision that was the result of the work of the highest scientific instruments purposely constructed for the destruction of mankind and mankind's defences.
Landing fairly upon the cup-shaped summit of the Observation Hill, it completely transformed the configuration of the landscape. Jagged scraps of sheet-iron and splintered baulks of timber flew high in the air, accompanied by a cloud of black smoke and dust. In an instant the pirates' carefully camouflaged observation post was wiped out, and with it the principal range-finding station of the secret base.
For the next half-hour the bombardment was hotly maintained. At first the pirates replied feebly, but by degrees they warmed to their task, working their 6-inch quick-firers well in spite of the numerous disadvantages under which they were placed.
One by one the concealed guns on the edge of the cliff were knocked out by direct hits upon the concrete gun-pits. Occasionally a battery would cease fire for about ten minutes; then the desperate gunners, who were fighting with halters round their necks, would re-man their weapons in the faint hope of "getting one home" on the daring destroyers which were rapidly approaching the island.
At length the 6-inchers of the secret base ceased to reply. Not a pirate remained in the emplacements save the dead and dying. The rest had fled to their deep subterranean retreats, whence by bombs and machine-gun bullets they still hoped to take a heavy toll of the invaders.
By ten in the morning the heavy gun-fire had almost died down. The cruisers had reduced distances to 2500 yards, and were occasionally firing mainly with the idea of keeping the pirates penned down to their underground shelters.
A quarter of an hour later the crews of the captured merchantmen, who were now able to roam at will over the north-western part of the island, noticed a destroyer negotiating the intricate passage between the reefs and the northern side of the secret base. She had run the gauntlet of the light quick-firers commanding the main approach channel, and had not come off lightly, for the funnels were riddled in several places, while there was a gaping hole in her hull just abaft her after torpedo-tube. Although the damage was mainly above the water-line, her powerful steam-pumps were hard at work.
She was no longer in danger of being under fire, for not a gun could be brought to bear upon her now that she had rounded the north-eastern extremity of the island. Moving slowly, and with the leadsman in the chains continually sounding, she weathered the north-western end of the island, and, lowering boats, dropped anchor almost directly abreast of the cave which Burgoyne had found so helpful during his preparations for flight.
Presently a rocket soared from the destroyer's deck taking with it a line that fell well beyond the edge of the cliff.
Instantly there was a rush on the part of the merchant seamen, and in twenty minutes four stout rope ladders afforded communication between the beach and the top of the cliff.