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## THE PAPER BOX.

(

Various Dissection Puzzles)

It may be interesting to introduce here, though it is not strictly a

puzzle, an ingenious method for making a paper box.

Take a square of stout paper and by successive foldings make all the

creases indicated by the dotted lines in the illustration. Then cut away

the eight little triangular pieces that are shaded, and cut through the

paper along the dark lines. The second illustration shows the box half

folded up, and the reader will have no difficulty in effecting its

completion. Before folding up, the reader might cut out the circular

piece indicated in the diagram, for a purpose I will now explain.

This box will be found to serve excellently for the production of vortex

rings. These rings, which were discussed by Von Helmholtz in 1858, are

most interesting, and the box (with the hole cut out) will produce them

to perfection. Fill the box with tobacco smoke by blowing it gently

through the hole. Now, if you hold it horizontally, and softly tap the

side that is opposite to the hole, an immense number of perfect rings

can be produced from one mouthful of smoke. It is best that there should

be no currents of air in the room. People often do not realise that

these rings are formed in the air when no smoke is used. The smoke only

makes them visible. Now, one of these rings, if properly directed on its

course, will travel across the room and put out the flame of a candle,

and this feat is much more striking if you can manage to do it without

the smoke. Of course, with a little practice, the rings may be blown

from the mouth, but the box produces them in much greater perfection,

and no skill whatever is required. Lord Kelvin propounded the theory

that matter may consist of vortex rings in a fluid that fills all space,

and by a development of the hypothesis he was able to explain chemical

combination.

[Illustration:

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