Lyle gun

Developed in 1877 by David A. Lyle, an Army Lieutenant, as a line-throwing short-barreled cannon designed to fire a projectile attached to a rope to a boat or victim in distress near the shore.

Projectiles for the gun were made of cast iron with a wrought iron eye bolt screwed into the base as an attachment point for the waterproofed braided linen line that had been carefully flaked in a special pattern in a flaking box to allow it to pay out freely. 

The messenger line fired to the distress site was then tied to a heavier line that was supported on land by an A frame crotch pole high enough to clear the surf so that a person could be transported to shore by a pulley on the line attached to a Breeches buoy. 

The Lyle Gun could shoot the projectile about 700 yards, although in actual rescues the practical range was much less.