Sometimes I am caught by a delightful fragment in a magazine, and blaze up into the fiercest interest, bestow maledictions on the delay which the intervening month creates, but am burnt out by the time it expires, and so lose the thread.

If you don't know the answer, take a guess.

VESTRY, a bandit confederation of practical jokists addicted to laying funny mud traps in thoroughfares for simple pedestrians to walk into.

The reason is that because strata are not unlimited in the horizontal direction and moreover are not horizontal, they may well come up against strata of a different age simply as a result of lateral displacement. The 'lateralists' have frequently pointed this out in relation to the history of the San Andreas fault.