Page:Popular Science Monthly Volume 10.djvu/745

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725
THE BALL-PARADOX.

gallantry, like his science, may be now a little out of date, but he manages at least to unite these two most opposite conversational ingredients in chemical union. When the lady would send him back from love-making to astronomy, he contrives to give both together, and, consistent to the close, takes leave of his charming scholar with the modest request that, as sole reward for his pains in teaching her the heavens, she will never again look on sun, moon, or stars, without thinking of him.

 

THE BALL-PARADOX.
By THOMAS S. CRANE, Mechanical Engineer.

THE exhibitors of the atmospheric air-brake, at the Centennial, attached a tube to the air-reservoir for the purpose of showing the immense pressure employed.

The current rushing from the small orifice of the tube sustains balls of varying gravities, according to the pressure applied.

Once, on accidentally resting the base from which the tube springs upon something lying on the table, it was found that, although no longer vertical, the current of air still held the ball in suspension, the ball revolving rapidly, and apparently hanging to the jet of air, which strikes the sphere at its upper side.

PSM V10 D745 The effects of fluid dynamics on gravity.jpg
Fig. 1.

It also makes little difference in the result whether the ball be a solid glass one an inch and a half in diameter, or a hollow rubber ball, or a solid wooden one three or four inches in diameter, the only variation being the distance at which the spherical body is held from the orifice.

When a glass ball with interior colored lines, such as children play with, is gently held in the current until the air has the sphere well in its power, it will rotate partly back and forth at first, and,