A visitor to Harvard asks a professor...

A visitor to Harvard asks a professor, "Excuse me, but would you be good enough to tell me where the Harvard Library is at?"

"Sir," came the sneering reply, "at Harvard we do not end a sentence with a preposition."

"Well, in that case, forgive me," said the visitor. "Permit me to rephrase my question. Would you be good enough to tell me where the Harvard Library is at, jackass?"