It is for the red and green lights, commonly known as the side lights, that the officer of the deck most intently watches (when the lookout warns him that lights are in sight), for by them he can tell which way the vessel is going. If her red light shows, he knows that her port side is toward him and she is crossing to his left; if it is her green light, her starboard side is toward him and she is crossing to his right; but if both the red and green are showing, she is heading straight in his direction.... If a vessel has another vessel in tow, she carries two masthead lights instead of one; and when a vessel is at anchor she has no side lights or masthead light, but a single white light made fast to a stay where it can be seen from all around her. In rivers and crowded harbors it is often impossible to follow the rules of the road; and sometimes even at sea the officer of the deck of one vessel discovers that the other is not heeding the rules. Then the steam-whistle is used to tell the other vessel what the first is doing. Thus, one whistle means “I am going to the right”; two whistles mean “I am going to the left”; and three whistles mean “I am backing”; while a series of short toots means “Look out for yourself; get out of the way!” There is one class of vessels which is most annoying to those who direct the course of large steamers. These are small fishing-vessels. On the Grand Banks of Newfoundland, on the coast of Spain, and on the coasts of China and Japan big fleets of these little vessels are found at all times. They show no lights at night, preferring to save the expense of oil, and take their chances of being sent to the bottom; but when they see a big ship rushing down upon them, they light a torch and flare it about. Often they pay for their folly with their lives. The torch is seen too late, or not seen at all, and the great iron bow of the steamship crushes into the frail little craft, perhaps cutting her clean in two; and the unhappy fishermen sink into the foaming wake of the churning propellers, leaving not a soul to tell their wives what became of them. [Illustration: ELECTRIC-LIGHT SIGNALS AT SEA: ARDOIS SYSTEM.]