The modern rifled gun is fired not by sight but by mathematics. The position of its target is found not by guess but by triangulation. Far away, on either side of land batteries are observers. The straight line from one to the other is the base line. As soon as they sight a ship, each turns his instruments on it and gets the angle from his end of the base line. The ship to be fired at is at the apex of the triangle thus obtained. The men at the guns get this position by telephone instantly. They know to a foot what their weapons’ elevation must be with a given charge of powder and a given weight of projectile to reach that distant spot. They set their mammoth piece, elevate it above the parapet on its lift, fire it and bring it back into concealment again. To bombard these base-stations from the sea was nearly futile. The shells that could sweep a fore-shore and make it untenable for an army might never find these few scattered, concealed men or these scattered, hidden, tiny stations. A whole fleet might rave at them for hours, and in vain. There was only one sure, quick way to cripple them.[97] _The Secret Attack on the Shore_ Far northward, miles outside of Boston Harbor, beyond the system of the harbor defenses, two ships stood into Nahant Bay, until they were within a line drawn from Fishing Point south of Swampscott to Spouting Horn on Nahant. Here, in 7 fathoms of water, they stopped and lowered their boats. Manned by crack bluejackets, whose oars were wrapped with cloth that they should not make a sound in the rowlocks, the cutters moved toward the beach at Little Nahant. Far away the harbor searchlights played like summer lightning. The sailors moved on in utter darkness, toward the invisible beach. They rowed in, in irregular formation, till they could hear the surf. Then the foremost boats lay still, tossing on the swell, waiting for the others to draw abreast. Formless, vaguely gray in the night, the line made a dash. They were on the first lifting swell of the long waves that tumble toward the land when a fierce white light tore terribly through the night, and blazed on them, and around them. It held them, intangibly, tightly, like the hand of a ghost. Orange flashes ripped through it. Little Nahant Beach quaked with explosion. In the white light, as if the tossing boats were spectral pictures in a dissolving view, they melted amid the roar of the shore-guns. Black fragments whirled through the steady glare, and shells chopped the sea where there were bobbing heads and clutching hands.