"It's all right," said Lennard, picking himself up. "Only a bruise or two; nothing broken. It seems to me that this new naval warfare of yours is going to get a bit exciting."
"Yes," said Erskine, "I think it is. Halloa, Great Cæsar! That must be that infernal invention of Castellan's brother's; the thing he sold to the Germans—the sweep!"
As he spoke a grey shape leapt up out of the water and began to circle over the Ithuriel. He snatched the transmitter from the hooks, and said, in quick, clear tones:
"Castellan—sink—quick, quick as you can."
The pumps of the Ithuriel worked furiously the next moment. Lennard held his breath as he saw the waves rise up over the decks.
"Full speed ahead again, and dive," said Erskine into the transmitter. "Hold tight, Lennard."
The floor of the conning-tower took an angle of about sixty degrees, and Lennard gripped the holdfasts, of which there were two on each wall of the tower. He heard a rush of overwhelming waters—then came darkness. The Ithuriel rushed forward at her highest speed. Then something hit the sea, and a quick succession of shocks sent a shudder through the vessel.
"I thought so," said Erskine. "That's John Castellan's combined airship and submarine right enough, and that was an aërial torpedo. If it had hit us when we were above water, we should have been where those French chaps are now. You're quite right, this sort of naval warfare is getting rather exciting."