Purchase a small crowfoot zinc and hang it about 1 in. above the half can. Prepare a 10 per cent solution of caustic soda and fill the jar within 1 in. of the top. Place on top the solution a thin layer of kerosene or paraffin. The cell will only cost about 50 cents to make and 25 cents for each renewal. When renewing, always remove the oil with a siphon. --Contributed by Robert Canfield, University Park, Colo.
Take 1/4 oz. of pulverized campor, 62 gr. of pulverized nitrate of potassium, 31 gr. nitrate of ammonia and dissolve in 2 oz. alcohol. Put the solution in a long, slender bottle, closed at the top with a piece of bladder' containing a pinhole to admit air, says Metal Worker. When rain is coming the solid particles will tend gradually to mount, little crystals forming in the liquid, which otherwise remains clear; if high winds are approaching the liquid will become as if fermenting, while a film of solid particles forms on the surface; during fair weather the liquid will remain clear and the solid particles will rest at the bottom.
A door lock may be lubricated by using some lead scraped from the lead in a pencil and put in the lock. This may be done by putting the scrapings on a piece of paper and blowing them into the lock through the keyhole.
Where bolts are subject to rust, the threads should be painted with pure white lead; then they will not rust fast.
When painting yellow pine exposed to the weather add a little pine tar with the priming coat.
** Revolving a Wheel with Boat Sails [152]
A novel windmill or revolving wheel can be made by placing a light wheel so it will turn freely on the end
[Illustration: An Unusual Type of Windmill]
of a post, and placing four small sailing boats at equal points on the rim of the wheel. It makes no difference which way the wind blows, the wheel will revolve in one direction. In Fig. 1 the direction of the wind is shown by the arrows, and how the sails catch the wind and cause the wheel to revolve. Figure 2 shows how the wheel will appear when complete. This device makes an attractive advertising sign.
A piece of iron placed in a coil of wire carrying a current of electricity becomes an electromagnet. If such a coil and iron core be made small enough they can be attached to a cork and the cork, floating on a solution, will allow the magnet to point north and south. The sketch shows how to make such an instrument. A coil of insulated wire is wrapped around a small iron core, leaving a few inches of each end free for connections. The insulation is removed