The deflection of the instrument is read by causing a beam of light from a lamp or candle to be reflected from the mirror to a scale located in front of the instrument. If the light from the lamp is allowed to shine through a small slit in a piece of dark paper, there will be a streak of light reflected upon the scale, instead of a spot.
To use this instrument in measuring larger currents than it will safely carry, connect it in parallel with another resistance which will carry the larger part of the total current. The galvanometer can be calibrated with this resistance, which is known as a shunt.
How to Make Advertising Lantern Slides
Procure some old discarded photographic films and remove the gelatin coating by soaking them in hot water. When dry, write the desired words on the thin celluloid and place it between two pieces of glass, lantern-slide size, and bind them as in making a lantern slide.
With the use of a carbon paper a very nice slide can be made by writing the words on a typewriter, and it will serve the purpose of an expensive announcement slide.—Contributed by F. P. Dickover, Atkinson, Neb.
Utilizing Old Brush Handles
The handle cut from an old dusting brush, fitted with the brass end of a shotgun shell, makes a first-class tool handle. The handle is cut off at A and the wood cut down to fit tightly into the brass shell.—Contributed by James M. Kane, Doylestown, Pa.
Tincture-of-iodine stains may be removed from clothing or the skin by using strong ammonia water.