Page:Popular Science Monthly Volume 10.djvu/749

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be now rapidly twisted by the thumbs and forefingers of both hands, the key wiil assume an horizontal position, and the string revolve in the form of a cone.

The friction of the jet must, therefore, tend to rotate a ball on an axis at right angles to the path of the jet, and, if this axis is not the shortest one passing through its centre of gravity, several oscillations, back and forth, must occur before the necessary adjustment is made.

When two balls of different densities are sustained by the same jet, it seems plain that each is sustained by the pressure of the air on the side opposite to the contact of the jet, for it is evident that, farther from the orifice, the jet has less power to displace the atmospheric pressure, and at that point the lighter ball only can be sustained.

In its rapid revolutions in such a jet of air as we have described, a light and hollow India-rubber ball affords a beautiful illustration of the flattening of the earth's poles by its revolutions on a free axis.




THE advancement of science is at once a glory and a disgrace to our modern civilization. It is glorious that so much has been done, but disgraceful that the public should be so often indifferent to the doing. In view of the benefits derived from scientific research, it would seem as if governments and communities ought to vie with one another in its encouragement. But, as a matter of fact, this assistance has in every country been unsystematic, meagre, partial, and infrequent. A museum may be equipped, perhaps, an exploring expedition fitted out, a geological survey established, or a party of astronomers sent forth to observe an eclipse or transit. Even these things are too often done grudgingly, and on a basis of false economy. Physics and chemistry, the two sciences most immediately bound up with modern progress, have received little or no public aid. No laboratory exclusively for research has yet been endowed either by national or private enterprise. Colleges enough have been founded, with laboratories more or less fitted for the work of routine instruction; but these are manifestly unsuited to the production of remarkably far-reaching results. Every great industry in America has been directly benefited either by one or the other of the two sciences in question; fortunes have been made from practical applications of their principles, and yet scarcely anything has been done for them in return. It would seem as if our manufacturers expected to get applications of science without any science to apply. Nearly all