This engraving is a perspective view of a simple and ingenious box, for making an alarm by a detonating ball. It is intended to be placed under a door or window. The box is quite small, being only one-third larger than the figure. A is an open bottomed wedge-shaped metal box, having a short lever jointed to it at B, near one end, the opposite . end of the lever being bent to a sharp angle atC. This lever fits to the hollow of the ing the thin end of the wedge beneath the door or line of the window, pressing the pointed end of the lever into the floor. This done, the box is raised to allow of a small detonating ball (torpedo) being dropped in between the lever and box. It will at once be observed that any person who may'tread upon the box, will press the topside of it down upon the lever, C, and compress Hie detonating ball (seen in dotted lines) so as to explode it and raise an alarm. In an attempt to push a door, or window with French sash open, theupptt side of the box will be pressed down upon the detonating ball, and explode it It also answers the pur- lieve, at no great cost It is the invention of W. A. Biddell, of London, who recently secured a patent.
This article was originally published with the title "Detonating Door and Window Alarm"