I am a light, exhibited to guide the mariner with a mark of distinction, to prevent h

I am a light, exhibited to guide the mariner with a mark of distinction, to prevent his mistake of other lights. I am exhibited to show the way, and not to be shown as a beacon to mark the way where there is already a sufficient number of beacons. I am exhibited to show the way, and not to point out where there are already sufficient marks to direct the course of the channel. I am a light, exhibited to direct the way, and not to