A little appliance devised for recording the opening of doors, etc., is shown in front elevation in the accompanying illustration. The device cousistsof a small clock-movement (preferably of the twenty-four hour type), the hour-wheel spindle of which is made to carry a light frame of brass or aluminium to hold a dial-card I). At one side of this dial is a standard B, of fairly stout sheet-brass, which is secured to the inside of the wooden case, andto which is pivoted a lever L, cut from sheet-brass. Attached to this is a spiral spring s, which draws downward the arm of the lever it is attached to, when a cord fixed to the end of the opposite arm is released. When the door to which the device is applied opens, a short length of soft blacklead pencil or a crayon inserted in a piece of thin tubing forming a holder on the lever at P describes a line on the dial-card. This indicates the hour of its occurrence, and also, as the dial rotates, the duration of time of such release, since the pencil-point, after moving from the centre, remains stationary at about J in. from the circumference of the card until the cord is again pulled taut. In fitting it up, the case of the instrument is secured lirmly to the wall behind the door.

A small hook is screwed in the latter, about lin. from the axial line of the hinges and also on a line with the hole in the case through which the cord passes. Then, the door being closed, the cord must be of' such a length as to retain the lever in the position shown in the illustration, when hooked on the door. The front of the case may be glazed if preferred. Dial-cards can be made of Bristol board, and the twelve (or twenty-four) hourly divisions should be drawn curved as shown, their radii being equal to the distance between the pencil-point and the fulcrum of the lever. Each division may be subdivided to denote halves and quarters, and numbered if necessary. Dimensions are not given, as they must be proportional to the size of the clock used.

Recording the Opening of a Door.