This was a signal that he and Jimmy had agreed upon. It meant, "Come! I want you," and when at home if Jimmy wished Bobby to come over to Skipper Ed's cabin, or Bobby wished Jimmy to come to Abel Zachariah's cabin, it was the way they called one another. And when the signal was heard, two shots were fired in quick succession to say, "I hear, and I will come," or two shots with an interval between, to say, "I hear you, but I can't come." Then it was the duty of the one who had fired the three shots in the beginning, whether or not his invitation had been accepted, to fire a single shot to say: "I hear you and understand."