246 



Mr. A. Mallock. The Physical [June 6, 



glass tube, A A, fig. 6, the lower end of which was ground flat and 

 cemented to a small plate of thick glass, B. The other end of the 

 tube was drawn out to a neck, the aperture being about 01 inch in 

 diameter. 



After the india-rubber was enclosed' and the plate B cemented on, 

 A was filled with water, great care being taken that no air bubbles 

 were enclosed. The neck was then closed by a ball of soft wax and 

 turpentine mixture, D, and the whole immersed in water in a cast- 

 iron cylinder (fig. 7), when it was subjected to a pressure of about 

 550 lbs. per square inch. 



Fig. 7. 



Under this pressure the water and india-rubber are somewhat com- 

 pressed. Since the wax and turpentine is soft, the glass tube 

 experiences but little difference of internal and external pressure, 

 the mixture flowing in through the neck of the tube and forming a 

 long filament, E, the volume of which represents the compression of 

 the contents of the tube. 



When the pressure is gradually removed this filament is partly 

 expelled, but retains its shape, and its length and sectional area being 

 known, the data are supplied for computing the volume elasticity of 

 the india-rubber. 



Let V be the volume of the tube A, 



V do. india-rubber, 



v do. the intruded wax, 



k' the volume elasticity of water, 

 k do. do. india-rubber, 



p the pressure in cylinder. 



