CORK, ITS MANUFACTURE AND PROPERTIES. 645 



effects of any given change of volume is to measure the ordinates of 

 the curve constructed by actual experiment. As may be supposed, the 

 pressures indicated by experiment are not nearly so regular and steady 

 as corresponding experiments in a gas would be, and the actual form 

 of the curves will depend on the quality of the cork experimented on. 



So far as preservation of elasticity during years of compression is 

 concerned, we have the evidence of wine-corks to show that a consid- 

 erable range of elasticity is retained for a very long time. With re- 

 spect to cork subjected to repeated compression and extension, there is 

 very little evidence to be offered beyond this, that cork which had 

 been compressed and released in water many thousand times, had not 

 changed its molecular structure in the least, and had continued per- 

 fectly serviceable. Cork which has been kept under a pressure of three 

 atmospheres for many weeks, appears to have shrunk to from eighty 

 to eighty-five per cent of its original volume. 



Mr. Anderson has brought under notice two novel applications of 

 cork to the arts : 



One is in the water-raising apparatus called a hydraulic ram, the 

 structure of which is shown by Fig. 7. The ram consists of an in- 

 clined pipe, A, which leads the water from a reservoir into a chamber, 

 B, which terminates in a valve, C, opening inward. Branching up 





Fig. 7. Cork in a Hydraulic Ram. 



from the chamber is a passage leading to a valve, D, opening outward 

 and communicating with a regulating-vessel, E, which is usually tilled 

 with air, but which the author prefers to fill with cork and water. 

 Immediately beyond the inner valve is inserted a delivery-pipe, F, 

 which is laid to the spot to which the water has to be pumped, in this 

 case to the fountain-jet in the middle of this pan. 



The action of the ram is as follows : The outer valve C, which 



