le, the point of which takes the weight, so that the
turbine becomes a top which can be kept spinning as long as the steam
supply lasts.

These toys, for such they must be considered, are very easy to make, and
are "warranted to give satisfaction" if the following instructions are
carried out.

A Small Top.--Fig. 74 shows a small specimen, which is of the
self-contained order, the boiler serving as support for the top.

[Illustration: FIG. 74.-Simplest form of steam top.] [1]

[Footnote 1: Spirit lamp shown for heating boiler.]

For the boiler use a piece of brass tubing 4 inches or so in diameter and 3
inches long. (The case of an old brass "drum" clock, which may be bought
for a few pence at a watchmaker's, serves very well if the small screw
holes are soldered over.) The ends should be of brass or zinc, the one
which will be uppermost being at least 1/16 inch thick. If you do not
possess a lathe, lay the tube on the sheet metal, and with a very sharp
steel point scratch round the angle between tube and plate on the inside.
Cut out with cold chisel or shears to within 1/16 inch of the mark, and
finish off carefully--testing by the tube now and then--to the mark.
Make a dent with a centre punch in the centre of the top plate for the top
to spin in.

[Illustration: FIG. 75.--Wheel of steam top, ready for blades to be bent.
A hole is drilled at the inner end of every slit to make bending easier.]

Solder the plates into the tube, allowing an overlap of a quarter of an
inch beyond the lower one, to help retain the heat.

The top wheel is cut out of a flat piece of sheet iron, zinc, or brass. Its
diameter should be about 2-1/2 inches, the vanes 1/2 inch long and 1/4 inch
wide at the circumference. Turn them over to make an angle of about 45
degrees with the spindle. They will be more easily bent and give better
results if holes are drilled, as shown in Fig. 75.

The spindle is made out of a bit of steel or wire--a knitting-needle or
wire-nail--not more than 1 inch in diameter and 1-1/2 inches long. The
hole for this must be drilled quite centrally in the wheel; otherwise the
top will be badly balanced, and vibrate at high speeds. For the same
reason, the spindle requires to be accurately pointed.

The steam ports are next drilled in the top of the boiler. Three of them
should be equally spaced (120 degrees apart) on a circle of 1-inch radius
drawn about the spindle poppet as centre. The holes must be as small as