The Clock that Had no Hands by Herbert Kaufman

A coal cart stopped before an office building in Washington and the driver dismounted, removed the cover from a manhole, ran out his chute, and proceeded to empty the load. An old negro strolled over and stood watching him. Suddenly the black man glanced down and immediately burst into a fit of uncontrollable laughter, which continued for several minutes. The cart driver looked at him in amusement. "Say, Uncle," he asked, "do you always laugh when you see coal going into a cellar?" The negro sputtered around for a few moments and then holding his hands to his aching sides managed to say, "No, sah, but I jest busts when I sees it goin' down a sewer."

The advertiser who displays lack of judgment in selecting the newspapers which carry his copy often confuses the "sewer" and the "cellar".