"It wasn't glass by any chance?" asked Tressidar.
"Glass?" repeated Mr. Greenwood. "Well, now I come to think of it, perhaps it did resemble glass. But why do you ask?"
"Because, judging by your description of its size and buoyancy, I am inclined to think that your mine was one of the glass buoys we use for marking the position of our submarine obstructions. After on-shore gales the coastguards find hundreds of them."
The narrator mopped his forehead. A wave of horrible uncertainty swept over him. Perhaps, then, the second episode of his nocturnal. adventures would have similar harmless interpretation?
"Carry on, pater," said Eric encouragingly.
"By Jove, sir!" exclaimed Tressidar, when Mr. Greenwood arrived at his discovery of the petrol-depôt. "Cut it short, if you don't mind. Let's have the salient facts. Every minute is of extreme importance."
Five minutes later the sub. was reporting the matter to the commander, who, in turn, communicated the discovery to the captain.
In ordinary circumstances the captain of the cruiser ought to have submitted a written report to the senior naval officer at Auldhaig, but red tape had long since gone by the board so far as naval matters were concerned. Other Government departments were still tied hand and foot with fathoms of red tape. Well it was that at the Admiralty the Gordian knot had been severed on that memorable 4th of August, 1914.
In a very short space of time the skipper's plans were formed. A landing-party, under the orders of Sub-lieutenant Tressidar, was to proceed at once to the solitary cottage. Since Mr. Greenwood was very hazy as to its locality, the assistance of the National Guard forming the coast-patrol was to be requisitioned.
Two pulling-boats, in charge of the first lieutenant, were to proceed to the bay where the entrance to the cave was situated. Mr. Greenwood's description of the spot was sufficiently accurate for the place to be identified. Examination of the chart showed that for miles northward from the entrance to Auldhaig Firth there was only water deep enough for a submarine to approach within easy distance of the shore at this particular indentation, which bore the name of Sallach Dhu Bay.