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, especially 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 kris to the ancient Greeks and 
Romans, and there is record of its use by them for the soles 
of shoes ae 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 caoutchouc are present also in many of 
our native plants having a milky juice, but the amount is 
' Pronounced koo’chuk. 
? Ch pronounced as in church, 
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