One of the great dangers to ships and steamers at sea is rocky shores, and sunken rocks on which ships may be driven by sea and wind, and sandbanks where they may stick because the water is shallow and be broken to pieces by the waves. In the daytime, sailors can see some of these dangers and keen out of the way, but in the dark nights, if they get out of their course, they may be wrecked, because they can see nothing. So lighthouses are built along the rocky coasts and on sunken rocks, to warn sailors of the danger.
A lighthouse is a tall tower built of stone. On the top of the tower, a great lantern is made of a frame of steel holding great plates of clear, strong glass. Inside this lantern, which is as big as a good-size room, is the lamp, set round with great glass and polished metal reflectors to increase the light. Oil is generally used in the lamp, but sometimes gas or electricity is also used.
A lighthouse is looked after by two men, who live in rooms at the top of the tower below the light. Lighthouses are built very high, partly in order that the light can be seen at a great distance, and partly to keep the light and the men out of danger of the waves when the sea is stormy. The life of lighthouse keepers is very lonely, for they often see no one for weeks; and so they are never kept long at a time in one lighthouse, but after a few weeks allowed to go home and other men take their place. It is their work to light the great lamp at night and to see that it burns well and steadily.
A ship’s captain can always tell, when he sees a light at night, which lighthouse it belongs to; because lights are not all the same. Some are steady light; many are revolving lights; that is, lights which turn round, and shine and stop shining every few moments or minutes. The captain watches the light, and if it appears every half minute, he knows it is one lighthouse; if it appears every fifteen seconds, he knows it is another; and so on.
Lighthouses prevent hundreds of wrecks and so save the sands of lives every year.