He reached up, and shook it.

It was loose.

He wrenched it out, and came back into the light.
"See! Nothing less than a chisel could have cut the mortar that way.
Miss Killigrew is right." He went back, and with the aid of the tongs poked into the cavity.

The wall of bricks was four deep, yet the tongs went through.

This business had been done from the other side.
"Well!" exclaimed the admiral, for once at loss for a proper phrase.
"You see, father?
I was right.