Frightfully aware of his filthy condition, he endeavored, as he wearily approached the master's desk, to rub some of the dirt off his hands... to no avail.
Presented with an impressively grimy hand, the schoolmaster fixed the lad with a steely eye. "Daniel," he declared with a frown, "if you can find another hand as dirty as that in this schoolroom, I'll let you off."
Thus challenged, Webster promptly produced from behind his back... his own left hand! "Here it is, sir!" he exclaimed -- and the teacher was obliged to keep his word.