He did not speak again for a full quarter of an hour, but he used the glasses often, always looking at the same spot on the western horizon. Robert was at last able to see a black dot there with his unassisted eyes, and he knew that it must be a ship.
"She's going almost due south," said the captain, "and in two hours we should overhaul her."
"Why do you wish to overhaul her?" asked Robert.
"She may be a privateer, a Frenchman, or even a pirate, and if so we must give the alarm to other peaceful craft like ourselves in these waters."
He raised the glasses again and did not take them down for a full five minutes. Meantime the strange ship came nearer. It was evident to Robert that the two vessels were going down the sides of a triangle, and if each continued on its course they would meet at the point.
The night was steadily growing brighter. The moon was at its fullest, and troops of new stars were coming out. Robert saw almost as well as by day. He was soon able to distinguish the masts and sails of the stranger, and to turn what had been a black blur into the shape and parts of a ship. He was able, too, to tell that the stranger was keeping steadily on her course, but the schooner, obeying her tiller, was drawing toward her more and more.
"They don't appear to be interested in us," he said to the captain.
"No," replied the man, "but they should be. They show a lack of that curiosity which I told you is necessary at sea, and it is my duty to overtake them and tell them so. We must not have any incautious ships sailing in these strange waters."
Ten minutes later he called the mate and gave a command. Cutlasses and muskets with powder and ball were put at convenient points. Every man carried at least one pistol and a dirk in his belt. The captain himself took two pistols and a cutlass.
"Merely a wise precaution, Peter," he said, "in case our peaceful neighbor, to whom we wish to give a useful warning, should turn out to be a pirate."