48 



GENERAL SCIENCE 



on its surface. When the needle breaks through the 

 film, it sinks quickly to the bottom. 



Experiment 5. - 

 Make a wire frame 

 in the form of a cube 

 similar to the one 

 shown in Figure 41 

 and dip it into a 

 strong solution of 

 soapsuds. Note the 

 tendency of the films 



FIG. 41. Interesting film forms may be obtained 

 by using wire frames of different shapes. 



to contract to the shortest lines between the different points of the 

 cube. 



Experiment 6. If, after blowing a soap bubble, one discon- 

 tinues before the bubble breaks from the tube, the bubble will 

 slowly decrease in size as the contraction of the film forces the air 

 out. 



How is shot made? 



Capillarity. - - The tendency of liquids to rise in hair- 

 like tubes is capillarity or capillary attraction. Capil- 

 larity takes place in all fibrous materials as well as in tubes. 

 The rise of sap in trees depends largely on this property. 



Experiment 7. Heat some soft glass tubing and draw it out 

 into smaller tubes. Break these tubes into pieces of four or five 



FIG. 42. Capillarity. 

 The water is lifted where it touches glass, while the mercury is depressed. 



inches in length. Hold them vertically and lower them into a 

 glass of water. Note the sudden rise of the water in the tubes 



