A man of letters was born in a small Scotch town, where his father wasthe intimate friend of a tradesman whom we shall call the grocer.Almost every day the grocer would come to have a chat with Mr. Mackay,and the visitor, alone of the natives, had the habit of knocking atthe door before entering. One day Mr. Mackay said to his daughter,"There's Mr. Macwilliam's knock. Open the door." But there was noMr. Macwilliam! He was just leaving his house at the other end of thestreet. From that day Mr. Mackay always heard the grocer's knock "alittle previous," accompanied by the grocer's cough, which waspeculiar. Then all the family heard it, including the son who laterbecame learned. He, when he had left his village for Glasgow,reasoned himself out of the opinion that the grocer's knock did heraldand precede the grocer. But when he went home for a visit he foundthat he heard it just as of old. Possibly some local SentimentalTommy watched for the grocer, played the trick and ran away. Thisexplanation presents no difficulty, but the boy was never detected.