6 2 o 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 HEREICK. 



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 instant- 

 ly 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 un- 

 supported 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 



