I could judge very nearly where it should appear, and I sounded the wall thereabout carefully both above and below without result.

Nor did any noise reach me to disclose a thinness of partition.
Convinced of the solidity of the wall at this spot I continued higher until I came to the end of the passage.

To my surprise the conditions here were practically the same.

Had I not entered at this point I could never have been convinced that there was an opening.

From within it defied discovery, for nothing confronted my eyes but mortared stone.