** How to Make a Miniature Stage [159]

A good smooth box, say 8 in. wide, 10 in. high and 12 in. long, will serve the purpose for the main part of this small theater.  Out two rectangular holes, Fig. 1, one in each end and exactly opposite each other.  Place a screw eye about 1/2 in. from the edge on each side of these openings.  Fit an axle in the screw eyes and fasten a spool to the middle of the axle.  On one of the two spools attach another smaller spool, Fig. 2, to be used as a driving pulley.  Cut out the front part of the box down to a level with the top of the spools.  Connect the spools with a belt made from tape about 3/4 in. wide.  On this belt fasten figures cut from heavy paper and made in the form of people, automobiles, trolley cars, horses and dogs.  A painted scenery can be made in behind the movable tape.  The front part of the box may be draped with curtains, making the appearance of the ordinary stage, as shown in Fig. 3.  A small motor will run the spools and drive the tape on which the figures are attached.  —­Contributed by William M. Crilly, Jr., Chicago.

[Illustration:  Details of Stage]

** A Floating Compass Needle [160]

When a thoroughly dry and clean sewing needle is carefully placed on the surface of water the needle will float even if the density of steel is 7 or 8 times that of water.  A sewing needle thus floating upon water may be used as a compass, if it has previously been magnetized.  The needle will then point north and south, and will maintain this position if the containing vessel is moved about; if the needle is displaced by force it will return to its position along the magnetic meridian as soon as the restraint is removed.

** Home-Made Dog Cart [160]

The accompanying photograph shows a boy with his “dogmobile.”  The photograph was taken when they were on a new pavement which had 2 in. of sand

Dog-Power Cart

left by the pavers and a grade of 6 per cent.  The machine is nothing more than a boy’s rubber-tired wagon on which are mounted a box for a seat and a wheel steering device extending above and below the board of the wagon.  The front wheels are guided by ropes attached from each end of the axle and a few turns around the lower end of the steering rod.  A pair of shafts are attached to the rear, into which the dog is harnessed.

** How to Make a Dry Battery Cell [160]

[Illustration:  Dry Battery Cell]

Dry battery cells are composed of the same materials for the poles, but instead of the liquid commonly used a paste is formed by mixing sal ammoniac and other salts with water and packed in the cell so it cannot spill.