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Page:Popular Science Monthly Volume 89.djvu/149

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Popular Science Monthly

��Rejuvenating Electric Lamps

DON'T throw away your burnt-out electric lamps. They can be re- newed by this simple method:

File off the tip carefully so that the globe does not crack. With a pair of tweezers, twist the broken filament together. Obtain from the druggist a piece of yellow phosphorus for five or ten cents. Insert a piece of it, about half the size of a pea, in the bulb. Cautiously heat the top of the globe by means of a Bunsen burner, and melt a piece of chemical glass over the hole, closing it completely.

The phosphorus unites with the o.xy- gen in the bulb to form phosphorus trioxide, a cloudy substance, which will settle in a few days. The globe is now filled with nitrogen.

The greatest caution must be exercised in the use of the phosphorus. It must be handled under water entirely, and with tweezers. Do not touch it.

An Exciter for Electroscopes

THE electrosta- tic exciter described in the October number of the Popular Science Monthly is rather too power- ful for use in charg- ing electroscopes. The following is a handy arrangement involving no risk of damaging the gold leaves.

Find a small glass jar without a neck, and coat with shellac inside and out. Attach a piece of fur inside the jar, the skin side next the glass using the same solution of shellac in alcohol, as an adhesi\-e. Select a small brass tube closed at one end, that will just slip in- side the fur, and after fitting in a .sound cork, insert a glass rod for a handle. Cover the cork with sealing wax.

Keep the metal tube inside the fur- lined jar when not in use. By merely withdrawing the former it will acquire a negative charge by rubbing against the fur. From the metal tube an electro- scope can be charged negatively by contact, or positively by induction.

���Exciting device

��Cariart of Dry Baffery Dip fhis end of Carbon in fbraffine

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��A few minutes' work makes a wet battery from a dry one

A Wet Battery From a Dry One

THE zinc and carbon of an exhausted dry battery may be used to make a wet battery, as shown in the illustration. The carbon should be o\en-baked to dry out all impurities. The bottom of the zinc can is removed and a number of wooden strips wedged in, as shown; the carbon should then be tacked in place. The upper end of the carbon is dipped in parafifine, to prevent creeping of the salt. After placing a solution of sal-ammoniac in the can, the zinc and carbon are inserted. — Filvnk Harazlm.

Interference of Lighting Circuit by Static Electricity

THE writer had an electric light that would not last more than an hour without burning out; but during the time that it was in use it gave a very bright light. About nine inches from the lamp cord a belt rubbed at a cross, producing static electricity by means of the friction at the cross. This condition was corrected as shown in the drawing: L is the light. B is the belt, crossing at C ; / is a piece of iron connected by a copper wire to a water pipe. G. C. is a ground clamp.

���One more static difficulty overcome

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