line is on a swivel, and every revolution is recorded on an instrument like a speedometer. When we look at that instrument we can tell how many miles we have made. ‘The quartermaster reads the log every hour and records the reading in this book. So we can tell pretty exactly how many miles we have traveled. We also know in what direction we went. But we can’t always tell how far wind and current have put us out of our true course. We make allowance for them when we figure our dead reckoning. Usually we hit it pretty closely. But if there comes a period when sun and stars are hidden for two or three weeks, as sometimes happens, a ship’s captain may be miles from where he thinks he is. Why, once we went after a steamer that sent an SOS for help, and we had a terrible time to find her because she was seventy miles from where she thought she was, and where we went to get her.”
“Gee whiz!” said Henry. “How did you ever find her?”
“I’ll have to tell you that some other time, Henry. I’m too busy just now.”
Henry went out on the bridge, so as to leave the captain undisturbed. It was still windy and cold, but the day fairly sparkled. The sun shone through a cloudless sky. The waves gleamed and flashed in its brilliant beams. As one spell-