But in less than a quarter of an hour the lieutenant's hopes were dashed to the ground, for instead of the Impregnable the stranger proved to be a steam yacht.
"May as well hail her; she might give us some information," muttered Drake, and turning to the chief petty officer he ordered the Mosquito to descend to within 50 ft. of the surface of the sea.
Gracefully the aerial craft swept towards the approaching yacht. Drake kept the latter well under observation with his glasses, looking so intently that the petty officer wondered what possessed him to take such an interest in a craft that certainly was not the pirate cruiser.
"By Jove!" thought the lieutenant. "I don't think I'm mistaken. That's the Serena."
During a previous commission on the North American station Drake had made the acquaintance of Mr. Rignold, and had frequently been his guest upon the yacht.
"If it is the Serena I'll have a yarn with Rignold for the sake of old times," he continued, then aloud he gave the order to bring the Mosquito down to the surface of the water.
The aero-hydroplane rested on the sea at a distance of about three hundred yards from the yacht's port bow. The Serena made no attempt to slow down, but her bulwarks were lined with men, who regarded the marine novelty with considerable interest. Drake noticed that in spite of the cold atmosphere the men were rigged out in canvas suits and red jersey caps, but by the aid of his glasses he discovered that the crew had donned the white suits over their thick clothing.
"Distinctly funny. Rignold never used to rig his men out like that," commented the lieutenant, "and he's got a pretty large crew on board. But perhaps the yacht's changed hands. I'll soon find out."
Meanwhile the Mosquito's aerial planes had been folded, and gliding rapidly through the water the little craft overhauled and gradually converged upon the stately yacht.
"Yacht ahoy!" bawled Drake. "Is that the Serena?"