280 INDUSTRIAL PLANTS 



clean the outer surface, are then flattened under pressure 

 with the aid of heat, and finally tied in bundles for shipment. 



By far the most important use of cork is for stoppers. It 

 is estimated that the daily consumption amounts to twenty 

 million. Cork stoppers are cut either by hand or by ma- 

 chinery. Large flat corks have to be cut so that the channels 

 pass from top to bottom. Such corks require, therefore, the 

 use of some sealing material such as wax, to make them 

 impervious. Smaller corks are cut so that the channels go 

 from side to side and hence are air-tight without sealing. 

 In the cutting, about half the material, or more, becomes 

 waste chips. So valuable are the properties of cork, how- 

 ever, that even in this form it may be utilized in important 

 ways. Thus, pulverized and mixed with rubber or with 

 boiled linseed-oil it forms when spread on canvas a floor cover- 

 ing at once durable and sound-deadening. Coarsely ground 

 cork serves well on account of its softness and elasticity 

 as packing for fruit, especiall}' grapes; and, when glued to 

 paper forms a safe wrapping for bottles in transportation. 

 The same remarkable properties make masses of cork most 

 effective buffers for vessels. In the form of thin sheets it has 

 long been used as a material for insoles and hat linings. The 

 lightness of cork has especially recommended it for artificial 

 limbs, handles, net floats, and life-preservers; while the uni- 

 form texture and the ease with which it may be shaped have 

 made it valuable to model makers and even to turners and 

 carvers. 



Although cork was known to the ancient Greeks and 

 Romans, and there is record of its use by them for the soles 

 of shoes and as stoppers for wine vessels, it has been generally 

 used only within the last few hundred years. 



76. Elastic gums, including india-rubber or caoutchouc ^ 

 and gutta-percha,- are tough, more or less elastic and water- 

 proof solids which separate as a curd from the milky juice 

 of a number of tropical plants. 



Small quantities of caoutciiouc are present also in many of 

 our native plants having a milky juice, but the amount is 



' Pronounced koo'ohuk. 



- Ch pronounced as in church. 



