"'THE BOTTOM'S ONLY ABOUT FIVE FEET DEEP.'"
They dropped lightly into the cavity. By the light of the torch they saw that on each side a flat circular wheel of stone, lacking one quadrant, moved on an iron axle in such a way that a half-turn of the hand-grip removed the support of the flagstone and allowed the corner to drop down. The flagstone was nicely balanced on a revolving iron rod let into a socket at each end. This contrivance formed the entrance to a narrow tunnel about four feet wide, and something over five feet high in the centre. Neither of the boys could stand upright in it. The floor was of hard-beaten earth; the walls and the arched roof were of ancient brick, covered with an incrustation of slimy moss.
"An old smugglers' tunnel, I'll be bound," said Armstrong. "It will be very odd if we have struck a lair of modern smugglers. Just look at your compass and see what direction it takes."
The needle swung almost perpendicular to the course of the tunnel.
"Eastward," said Warrender. "That's strange. I thought it probably ran south, to somewhere near that place at the end of the island where we saw the marks of a boat the other day."
"It seems to shelve downward slightly. Looks as if it runs under the channel."
"Towards Pratt's uncle's grounds. Let's explore."
"Better switch off your light, then. We can find our way in the dark by touching the sides."
They went forward in single file, stepping gingerly, and bending their heads to avoid the roof. The air smelt musty and dank, and was unpleasant and oppressive. For a time the floor sloped gently downwards, but presently they were aware that it had taken an upward trend.