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THE POPULAR SCIENCE MONTHLY. 



mixture of soap and sugar with water. On withdrawing the 

 frame its inner space will be occupied with a flat film of so little 

 weight that it does not visibly sag, but becomes more tense as it 

 is attenuated. A closed contour of cotton or silk thread laid upon 

 the film will lie in any form so long as the film is whole and its 

 tension equal in every direction. But the instant it is broken 



Pig. 2.— Copper King floating on the Surface of Water. 



within the contour the thread will stretch and assume a circular 

 form as in Fig. 5, under the influence of the outward tensions of 

 the rest of the film. It takes the shape in which it bounds as 

 great a surface as its length permits, which is that of a circle. 

 Prof. Schoentjes has varied upon this experiment by using, instead 

 of a simple thread, a system composed of portions of rectilinear 

 solids and portions of arbitrary form, made by passing threads 

 loosely through pieces of fine straws (as in the object lying on the 

 table in Fig. 5). This being placed upon the film and the film 

 pierced, as in the previous experiment, invariably assumed a 

 shape in which all the loose thread portions became arcs of a 

 single circumference, of which the rectilinear solid portions (the 

 straws) constituted chords — or the figure, according to Steiner, 

 of the maximum surface that can be limited by a contour so 

 composed. M. Terquem and M. Gossart, by breaking the film at 

 one or more points outside of the contour, make the thread double 

 into loops. 



M. Gossart has studied the pressure of this supposed mem- 

 brane surrounding the drop of water, and its variation under dif- 

 ferent degrees of curvature. Investigating its behavior in a 



