"By Jove!" he murmured. "I never noticed that before."
The feature which so earnestly claimed his attention was a deep ledge, directly over the mouth of the cave, but some forty feet from the ground. Behind it the wall of rock sloped darkly inwards, suggesting a recess extending by haphazard computation at least a couple of yards. It occurred to him that perhaps the fault in the interior of the tunnel had its outcrop here, and the deodorizing influences of rain and sun had extended the weak point thus exposed in the bold panoply of stone.
He surveyed the ledge from different points of view. It was quite inaccessible, and most difficult to estimate accurately from the ground level. The sailor was a man of action. He chose the nearest tall tree and began to climb. He was not eight feet from the ground before several birds flew out from its leafy recesses, filling the air with shrill clucking.
"The devil take them!" he growled, for he feared that the commotion would awaken Iris. He was still laboriously worming his way through the inner maze of branches when a well-known voice reached him from the ground.
"Mr. Jenks, what on earth are you doing up there?"
"Oh! so those wretched fowls aroused you?" he replied.
"I had a fancy to roost by way of a change"
"I am more than serious. This tree grows a variety of small sharp thorn that induces a maximum of gravity--before one takes the next step."
"It is sheer lunacy, I admit. Yet on such a moonlit night there is some reasonable ground for even a mad excuse."
"Mr. Jenks, tell me at once what you are doing."
Iris strove to be severe, but there was a touch of anxiety in her tone that instantly made the sailor apologetic. He told her about the ledge, and explained his half-formed notion that here they might secure a safe retreat in case of further attack--a refuge from which they might defy assault during many days. It was, he said, absolutely impossible to wait until the morning. He must at once satisfy himself whether the project was impracticable or worthy of further investigation.
So the girl only enjoined him to be careful, and he vigorously renewed the climb. At last, some twenty-five feet from the ground, an accidental parting in the branches enabled him to get a good look at the ledge. One glance set his heart beating joyously. It was at least fifteen feet in length; it shelved back until its depth was lost in the blackness of the shadows, and the floor must be either nearly level or sloping slightly inwards to the line of the fault.