Amulet of the Long Offing

Sea-worn glass caged in silver wire, clear as still air at the center and milky all round the rim.

Each charge fixes one distant thing in the wearer's sight for an hour, and holds it there after it drops below the horizon, enters cover, or passes out of any light. When depleted the milky rim closes in until only a pinprick of clear glass remains, and through that pinprick the wearer still sees three miles as plainly as thirty feet.