Deriving long use from an umbrella depends in part on proper selection, care of the cloth and frame, and precautions against loss or theft. A silk cover is desirable to shed rain, and a cotton one for a sunshade. The hot sun dries out the silk and heats the metal ribs under it, quickly destroying it. If silk is used for sun protection, wet the cover occasionally. Always set an umbrella to dry, handle down if there is not space to dry it open.
A broad ribbon loop on the handle of a woman’s umbrella permits carrying it on the wrist and prevents forgetting it. An umbrella with a removable handle can be folded into a suitcase, and putting the handle in the pocket when leaving the umbrella in any public place makes it less liable to theft. An umbrella should bear the name and address of the owner.
A Bell-Ringing Mail Box
The annoyance of watching for the arrival of the mailman was overcome by the fitting of an electrical alarm to the mail box, as shown in the sketch. A strip of metal, A, was pivoted in the box and weighted on one end. A bell, B, was wired to dry cells in the box below the container for the mail. When the mail is dropped in the box the end A is forced down, forming an electrical contact and completing the circuit from the cells C through the wire D and back through the wire E. When the mail is removed the weight raises the metal strip.—James E. Noble, Portsmouth, Canada.
A Simple Polarity Indicator
An ordinary compass, fitted flush in a wooden frame as shown in the sketch forms the basis for the polarity indicator described. The N, or north, and S, or south, points of the compass should run lengthwise with the frame with the former on the end farthest from the binding posts, C and D. Five turns of No. 18 gauge, or any similar wire are wound lengthwise around the frame and over the compass. The ends of the wires terminate at the two binding posts. Begin at C and wind toward the compass, binding the wire at D.
If the two ends of a wire are free, and it is desired to know whether there is any current present, and if so, its polarity, fasten one wire to the post C and the other to D. Before connecting the wires, hold the compass and frame in such a way that the needle is over the N point on the compass dial. If, after the wires are connected, the needle moves, there is a current flowing. If the needle is deflected toward the east, the negative wire is on C; if it is deflected toward the west, the positive wire is on C.
When it is desired to ascertain the polarity of a wire, which is covered by a floor, ceiling, or molding, hold the compass as explained, and either directly above or below the wire. Then turn on the current. If the instrument is above the wire, the wire extending parallel with it north and south, and the needle is deflected toward the west, the current is flowing from the north to the south end of the wire. If the wire runs east and west and the needle is deflected to the west, the current is running from west to east.