Illuminating an Outside Thermometer
During the season of furnace fires the thermometer outside the north window becomes of added interest and usefulness in helping one to judge the proper draft adjustments of the furnace for the night. A pocket electric flashlamp is convenient for examining the thermometer after dark, but it is not always at hand, matches are dangerous when lace curtains are at the window, and besides, the reflection from the glass of both matches and flashlamp on the inside makes it very difficult to read the thermometer.
To avoid these difficulties I attached to my thermometer the device shown herewith, which consists of a miniature battery lamp placed at the back of the translucent-glass thermometer and operated by a battery within the house, the light being turned on by an ordinary push button placed conveniently inside of the window.
A strip of brass, A, 3/8 in. wide by 1/16 in. thick, was riveted (soldering will do) to the lower support of the thermometer. The free end of this brass strip was bent around a disk of hardwood, B, and fastened to it by three or four small screws in such a manner that the disk made a circular platform just behind the thermometer scale. This disk was slightly larger than the mouth of a small, thin tumbler. On the upper surface of this disk was fastened with shellac and small nails close to the periphery, a disk of cork, 1/4 in. thick, this cork disk being a close fit for the mouth of the tumbler. A miniature porcelain electric-lamp socket was fastened with screws on the cork of the base. Wires were then run from the lamp socket through the cork and wood disks and the whole painted with melted paraffin to close all apertures and keep out moisture. Good rubber-covered electric-light wire will do nicely for the wiring outside the house, although, if it can be obtained, a piece of lead-covered paired wire is preferable. These wires must be only long enough to reach inside the house, where they may be joined to the ordinary sort of wire used in electric-bell work for connecting with push button and battery.
A 4-volt lamp of about 2 cp. will be sufficient to illuminate the thermometer and allow the scale and mercury column to be distinctly seen. It may be found necessary to make some adjustment by bending the brass strip in order to bring the lamp centrally behind the scale and at the proper height to give the best lighting on the range of from 10 to 40 deg. Over the lamp is placed the tumbler for protection from the weather, and, if desired, half of the tumbler may be painted as a reflector on the inside with white enamel paint, although, in practice, I have not found this necessary.
Within the house the push button should be placed at the window where it can be most conveniently reached when viewing the thermometer, and connections may be made to the battery regularly used for ringing the house bells, or to a separate battery of, say, 4 dry cells, placed in some location, as a closet, near the thermometer.—Contributed by C. F. A. Siedhof, Winchester, Mass.