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Page:Popular Science Monthly Volume 36.djvu/638

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THE POPULAR SCIENCE MONTHLY.

guidance in practice"—a remark which may be interpreted as a tacit indorsement of the ascription; whereas it referred to the fact that he had recognized for the present (though not for the future) no guidance whatever beyond that of empiricism. Doubtless there may be other side-issues which I do not perceive. But no number of such can change the verdicts on the main issues. That Prof. Huxley's two characterizations of the political doctrine I hold are contradictory, is undeniable. That his description of my "way of thinking" is utterly at variance with the evidence as presented in my books, is no less demonstrated. And it is equally certain that the conceptions of right treatment, medical and political, which he ascribes to me are opposite to those I have myself set forth.—Nineteenth Century.

 

THE LAWS OF FILMS.
By SOPHIE BLEDSOE HERRICK.

THERE is scarcely anything in the world which seems more utterly outside the realm of law than a soap-bubble. The delicate film, with its exquisite floating colors, its power of instantly vanishing, leaving no trace behind, hardly seems as though it could form a link in the inexorable chain of cause and effect which we call physical law.

The atmospheric pressure on a bubble six inches in diameter is over fifteen hundred pounds, and yet the fragile film lies safely between the opposing forces of nature—the pressure of the outer air, the spring of the inclosed cushion within it, the downward pull of gravity, the upward push of the buoyant atmosphere, and the molecular forces in the film itself: so long as the bubble lasts; it is because of an exquisite adjustment of all the forces, physical and molecular, concerned in its existence.

This is, of course, the merest commonplace, and yet it is one of the commonplaces of nature, which, however well we may know them, never cease to be wonderful when they are in any degree realized. There are other laws governing films which are no less wonderful, though they are less familiarly known. A heap of bubbles blown while the pipe is dipped under the surface of soapy water looks like a chaotic huddle of bubbles of all sizes and many shapes; but, upon careful examination, it is found that never more than three films meet at an unsupported liquid edge, and never more than four edges meet at a liquid point, and that the angles are always equal; that is, films will not meet each other at an unsupported edge or point at an angle smaller than 120°—one third of a circle.

Ordinary soap-suds made with clean hot water and ivory or