** Ringing a Bell by Touching a Gas Jet [403]

The experiment of scuffling the feet over a carpet and then producing a spark which will light the gas by touching the chandelier is described on another page.  One of our correspondents says that if a wire is connected to the chandelier and led to one terminal of the coherer of a wireless telegraph outfit the bell will ring every time the

[Illustration:  Touch the Gas Jet and Ring the Bell]

spark is produced by touching the chandelier, and that, as the chandeliers are all connected by the gas-pipe, the bell will ring, no matter in which room the spark is produced.

** Lead Kills Knots [403]

The covering quality will be greatly improved if some dry red lead is added to the shellac varnish used for killing knots.

** How to Make a Wood Turning Lathe Out of an Old Sewing Machine [403]

With a hack-saw, cut off the arm containing the needle on line ab, Fig. 1, leaving the shaft only.  On the end of the shaft will be found a round plate,

[Illustration:  Fig. 1]

in which drill four 3/16-in. holes.  Now secure, or have turned, a piece of iron or steel 1-1/2 in. in diameter, Fig. 2.  Drill and countersink four 3/16-in. holes in it to fit the holes on the shaft plate.  File a spur center 5/16 in. long, and two side points 3/16 in. long.  Bolt this plate to the shaft plate with four flat-headed stove bolts, 3/16 in. in diameter by 5/8 or 3/4 in. long, Fig. 3.

For the bed, use a board 32 in., long and as wide as the base of the machine arm.  This gives a limit of 2 ft. between spur and dead centers.  Let this board be made level with the rest of machine table by making a pair of legs if needed.  Next make a T-rail, Fig. 4, of two boards, one 5 by 3/4 by 32 in., the other 3-1/2 by 3/4 by 32 in.  Threequarter inch of the wider board projects over each of the smaller boards.  Nail firmly and clinch nails, or screw together.  Screw this rail on the machine board so that its center coincides exactly with the machine centers.  Bore a number of 3/8-in. holes with centers 2-3/4 in. apart along the center line of this rail, beginning 6 in. from the end nearest the machine.  Make another T-rail for slide tool rest, of two pieces 32 by 3 by 3/4 in., and 32 by 1-1/2 by 3/4 in.  Fasten this in front of the larger T-rail and parallel to it, the center lines being 6-1/2 in. apart.

To make the tail-piece, that is, the part to hold wood to be turned, get a board 6-1/2 by 7 by 3/4 in., and on the edges, Fig. 5, A, screw two pieces 7 by 3/4 by 1-1/2 in. so that the cap thus made will fit snugly over the large T-rail.  Fasten to these last two pieces,

[Illustration:  Fig. 4]

with screws, two more pieces 7 by 3/4 by 3/4 in., Fig. 5, B. This tail-piece should move smoothly back and forth with no side motion.  Now get a block of hardwood 4 by 2-1/4 in., and 1-3/4 in. higher than the spur center when mounted on the middle of the tailpiece just described.  At exactly the height of the spur center bore through this block a 3/4-in. hole, Fig. 5.  Have