An Alternative Arrangement.—­If the reader prefers a steam pump which will work at slow speeds, and be available, when not pumping, for driving purposes, the design may be modified as shown diagrammatically in Fig. 114.  The striker becomes a cross head, and is connected by a forked rod passing on each side of the pump with the crank of a fly wheel overhanging the base.  The valve is operated in the ordinary manner by an eccentric on the crankshaft.  The steadying effect of the fly wheel and the positive action of the valve make it possible to use a larger pump plunger than is advisable with the striking gear.  With a pump piston of considerably greater diameter than the piston rod, the pump may be made double-acting, a gland being fitted at the front end for the piston rod to work through, and, of course, a second set of valves added.

[Illustration:  Fig. 114.—­Plan of steam pump with fly wheel.]

A SUGGESTION.

For exhibition purposes a small, easily running, double-action pump might be worked by the spindle of a gramophone.  A crank of the proper throw and a connecting rod must be provided.  Both delivery pipes feed, through an air-chamber, a fountain in the centre of a bowl, the water returning through an overflow to the source of supply, so that the same water may be used over and over again.

XXIII.  KITES.

Plain Rectangular Box Kites.—­The plain box kite is easy to make and a good flier.  Readers should try their hands on it before attempting more complicated models.

Lifting pressure is exerted only on the sides facing the wind, but the other sides have their use in steadying the kite laterally, and in holding in the wind, so that they justify their weight.

Proportions of Box.—­Each box has wind faces one and a third times as long as the sides, and the vertical depth of the box is about the same as its fore and aft dimensions.  That is, the ends of the boxes are square, and the wind faces oblong, with one-third as much area again as the ends.  Little advantage is to be gained from making the boxes proportionately deeper than this.  The distance between the boxes should be about equal to the depth of each box.

CONSTRUCTION.

After these general remarks, we may proceed to a practical description of manufacture, which will apply to kites of all dimensions.  It will be prudent to begin on small models, as requiring small outlay.

Having decided on the size of your kite, cut out two pieces of material as wide as a box is to be deep, and as long as the circumference of the box plus an inch and a half to spare.  Machine stitch 5/8 inch tapes along each edge, using two rows of stitching about 1/8 inch from the edges of the tape.  Then double the piece over, tapes inside, and machine stitch the ends together, three quarters of an inch from the edge.  Note.—­All thread ends should be tied together to prevent unravelling, and ends of stitching should be hand-sewn through the tape, as the greatest strain falls on these points.