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.