I am a light set up to warn and guide. I mark where dangers are to be avoided. I show

I am a light set up to warn and guide. I mark where dangers are to be avoided. I show the way where safety lies. I am the beacon, which indicates the channel. I am the light buoy, which marks the place of anchorage. I am exhibited, to prevent ships from running foul of one another, and thereby sustaining damage. I exhibit false lights, where mariners must not come. I am exhibited, to show where they may come, and be safe.