Fig. 17.
Fig. 18.
It is now ready for the motive power, which is obtained by the falling of sand, as in the hour-glass. The sand must be first well washed, dried, and sifted, to remove all stones, then poured through the case top to within two inches of the cross-bar (C, [Fig. 18]), the weight resting on the surface. As the sand runs through the funnel-point the weight will descend with it at the rate of about 1 in. per hour. The flow of sand will be perfectly equable from the time the case is filled until it is nearly empty, which is explained by the fact that the sand lies in a succession of conical heaps, only the first of which presses on the bottom, the others throwing their weight on the sides of the case. A gallon of sand will be more than sufficient to fill the cases, and as it falls it should be caught in a vase placed beneath for that purpose. In winding up the clock the inside weight must be raised to the cross-bar by pulling down the bullet end of the cord, and the sand poured through a paper funnel into the top of the case, care being taken to set the hand to the right hour. A clock of the dimensions here given will work for about twelve hours, but by lengthening the sand-box the working hours will be increased in proportion. It will save time and trouble to have a double supply of sand and two vases, and use them alternately. Of course one does not pretend that such a simple clock as this will keep accurate time.
CHAPTER VIII.—HOW WE MADE A CHRISTMAS SHIP.
By C. Stansfeld-Hicks, Author of Yacht and Canoe Building, &c., &c.
‘What shall we do to amuse the boys?’ was the question asked at a friend’s house. ‘They are tired of Christmas trees, and it is so difficult to think of anything new.’
‘Well,’ I suggested, ‘why not have a Christmas ship?’
A Christmas ship! We never heard of such a thing! What is it?’