Read it through once

A buoy is nothing but a board four or five feet long, with one end turned up; it is a reversed school-house bench, with one of the supports left and the other removed. It is anchored on the shoalest part of the reef by a rope with a heavy stone made fast to the end of it. But for the resistance of the turned-up end of the reversed bench, the current would pull the buoy under water. At night, a paper lantern with a candle in it is fastened on top of the buoy, and this can be seen a mile or more, a little glimmering spark in the waste of blackness.