I am a light, set up to guide and warn. I am a mark, which shows how far the false li

I am a light, set up to guide and warn. I am a mark, which shows how far the false lights of false beacons are exhibited, and how far they are to be trusted. I am a beacon, which shows how close a mark must be exhibited, to show where true lights are erected, and how far they may be depended upon. I am a light, which exhibits false lights as false guides, and true lights as true guides, to mark the sea