174 VEGETABLE SUBSTANCES. 



stoppers are rendered still more efficient by a thin 

 coating of caoutchouc on the upper part, which 

 securely protects the cement from being acted upon 

 injuriously, it having been found that the carbonic 

 acid gas generated by the damp arising in wine- 

 vaults has a tendency to decompose the cement and 

 to cause a separation of the parts. 



An instrument was invented some years ago to cut 

 cork for stoppers by machinery. This was so con- 

 structed as to cut spirally, producing smooth, even, 

 and nearly cylindrical pieces ; but these not tapering 

 sufficiently there being scarcely any difference be- 

 tween the top arid the bottom and this defect not 

 being remediable by any arrangement of machinery, 

 the invention was found to be of little or of no prac- 

 tical utility. 



Cork is admitted into England at an importation 

 duty of Ss. per cwt., the price of the best being about 

 4i for the same quantity : 42,685 cwt. were imported 

 into England in 1832. 



The best cork is brought from France ; that which 

 we receive from Spain and Portugal being not more 

 than a half or a third of the value of good French 

 cork-wood. 



Where the bark of the quercus suber cannot be 

 obtained, many substitutes have been found to supply 

 its place, among the spongy bark or woody substance 

 of other trees. The bark of the black poplar is 

 employed by the Cossacks for stoppers to their flasks. 

 Aeschynomene lagenaria is applied to the same pur- 

 pose in Cochin China, and the hibiscus cuspidatus 

 in Otaheite. In many parts of the West Indies the 

 wood of the alligator pear-tree is made a substitute 

 for cork, which it resembles so much in its levity, and 

 other properties, that it has likewise received the 

 name of the cork-wood tree. 



