Cabrillo National Monument

This guide to Cabrillo National Monument in San Diego opens with a marvel of French physics lit on this cliff in 1855: a Fresnel lens, invented decades earlier by Augustin Fresnel, shipped from Paris at enormous cost and mounted four hundred twenty-two feet up on the theory that higher meant farther. It follows the keepers who worked it and the assumption behind its placement, and the shotgun blasts they resorted to firing into the dark when ships kept missing the harbor anyway. Look toward the water and imagine the fog rolling in exactly where that beam needed to travel.