ANIMAL-TRAP
The animal, in seeking to escape, completes its own capture.
The animal enters through one of two front apertures and steps on a tilting treadle. The treadle turns a rock-shaft by means of chains, sliding a semicircular plate over the aperture behind the animal while leaving the other aperture open for the next arrival. Seeking a way out, the animal jumps onto a bait box, raises a hinged drop-door, and falls down an inclined spout into a rear holding compartment from which it cannot return. The trap is then set for the following animal.
“In seeking to escape the animal jumps upon the top of the bait-box, raises the drop-door S, and jumps or falls into the rear compartment of the trap, whence he cannot escape.”— Russell Elliott, from the specification
And the world did not beat a path to his door.