After luncheon I went below and directly to the end of the corridor, and began to sound the walls. To the eye they were all alike, being of cement, and substantial enough. Through the area window I saw the solid earth and snow; surely there was little here to base hope upon, and my wonder grew at the ease with which Morgan had vanished through a barred window and into frozen ground. The walls at the end of the passage were as solid as rock, and they responded dully to the stroke of the hammer. I sounded them on both sides, retracing my steps to the stairway, becoming more and more impatient at my ill-luck or stupidity. There was every reason why I should know my own house, and yet a stranger and an outlaw ran through it with amazing daring. After an hour’s idle search I returned to the end of the corridor, repeated all my previous soundings, and, I fear, indulged in language unbecoming a gentleman. Then, in my blind anger, I found what patient search had not disclosed. I threw the hammer from me in a fit of temper; it struck upon a large square in the cement floor which gave forth a hollow sound. I was on my knees in an instant, my fingers searching the cracks, and drawing down close I could feel a current of air, slight but unmistakable, against my face. The cement square, though exactly like the others in the cellar floor, was evidently only a wooden imitation, covering an opening beneath. The block was fitted into its place with a nicety that certified to the skill of the hand that had adjusted it. I broke a blade of my pocket-knife trying to pry it up, but in a moment I succeeded, and found it to be in reality a trap-door, hinged to the substantial part of the floor. A current of cool fresh air, the same that had surprised me in the night, struck my face as I lay flat and peered into the opening. The lower passage was as black as pitch, and I lighted a lantern I had brought with me, found that wooden steps gave safe conduct below and went down. I stood erect in the passage and had several inches to spare. It extended both ways, running back under the foundations of the house. This lower passage cut squarely under the park before the house and toward the school wall. No wonder my grandfather had brought foreign laborers who could speak no English to work on his house! There was something delightful in the largeness of his scheme, and I hurried through the tunnel with a hundred questions tormenting my brain. The air grew steadily fresher, until, after I had gone about two hundred yards, I reached a point where the wind seemed to beat down on me from above. I put up my hands and found two openings about two yards apart, through which the air sucked steadily. I moved out of the current with a chuckle in my throat and a grin on my face. I had passed under the gate in the school-wall, and I knew now why the piers that held it had been built so high,—they were hollow and were the means of sending fresh air into the tunnel.