Fig. 155
"Well," said Harold, "I propose an electric trap which shall have two compartments. We will keep cheese in the inner compartment, the walls of which shall be of wires so that the rats may see the cheese. The floor of the outer apartment shall be covered with wire, as shown in [Fig. 154]. The wires of the secondary circuit from the bell ([Fig. 156]) shall be fastened to the binding posts b and c ([Fig. 154]). The partition d shall be a swing door into the apartment A where the cheese is. This is shown in profile in [Fig. 155]. d must act as a switch to close the primary circuit through the bell P ([Fig. 156]). We will have three dry cells in the primary circuit. Now this is the way it will work: A rat comes up from under the mill with wet and slimy feet—just suited for making contact for the electric current to enter his body. The smell of the cheese attracts him. He circles around the trap several times, watching the cheese in apartment A through the wire screen. He sees a narrow opening into this apartment under the door d. He puts himself in position upon the floor of the outer apartment B, his feet bridging the gaps between the two systems of wires belonging to the secondary circuit. When he thrusts his head under the door and pushes it, it swings in a little, bringing one metal strip against another, which belongs to the primary circuit. This closes that circuit. He will never hear the bell ring, for the electric current which will shock him to death travels 186,000 miles per second, while his sensations travel only sixty miles an hour. If the involuntary recoil of his muscles does not make him jump back, so that the door will shut and stop the bell from ringing, Dyne will be awakened and he will close the door, since we will put the trap at that hole where the rats enter his bedroom."
Fig. 156
The next night three rats were electrocuted by this device.
I told the boys they had so many interesting things going on at the mill that we should have to have a telephone between it and the cottage so that we could talk them over.