At last I understood.

The bowl had worn away on one side, and the silver rim had been needed to keep the tobacco in.
Undoubtedly this was the explanation, for even before the rim came I was a little puzzled by the taps of the brier.

He never seemed to hit the wall with the whole mouth of the bowl, but of course the reason was that he could not.

At the same time I do not exonerate him from blame.

He is a clumsy smoker to burn his bowl at one side, and I am afraid he lets the stem slip round in his teeth.