"You see, he was in charge of the camp."
"You mean he oughtn't to have come at all?"
"Naturally he thought it would please you and Mrs. Crawshay, but----"
"Oh!"
The girl said no more.
"She thought I was jealous, or huffy, or something," Warrender confided to Armstrong later. "I wonder what she'd have said if I'd told her that the idiot had never run a motor-boat before?"
CHAPTER XVII
THE TOPMOST ROOM
It was in the evening twilight that Armstrong and Warrender put off in the pram for their second expedition to the tunnel. On reaching the ruins, Warrender posted himself in one of the lower rooms, while Armstrong mounted to the upper floor, intent on discovering the source of the ghostly moans. Climbing out of the window opening, and pulling aside the ivy, he found that steps had been made in the brickwork of the crumbling wall, by means of which any one with a steady head might with ease ascend to the roof. And there, behind one of the gables, partly protected from the weather, he came upon a long metal organ pipe laid flat, and near it a large funnel-shaped object. A strong breeze was blowing from the south-west, but the organ pipe gave forth no sound.
Still puzzled as to the manner in which the sound was produced, and reflecting that Pratt would probably have jumped to it at once, Armstrong heard a low whistle from below. He scrambled hastily down, and had only just slipped into the eastern room when he heard lumbering footsteps upon the stairs. From the doorway he watched the man whom he had seen in the morning. A minute or two after the new-comer had entered the western room, the moaning broke out. Armstrong waited until the man had descended and all was quiet again, then once more climbed upon the roof. The mystery was solved. The funnel had been so adjusted as to catch the wind, and direct it with some force into the mouth of the organ pipe. It turned like a weather-cock, so that the sound was independent of the veering of the wind.