254 TIMBERS AND THEIR USES 



Cork is a valuable econonoic commodity 

 because of its imperviousness to moisture, its 

 elasticity and firmness. Mr. Leroy Sargent 

 gives the following interesting account of the 

 uses, growth, and harvesting of cork : " In the 

 young tree the first few layers of cork are com- 

 paratively thick, while those formed later are 

 only about 1 to 2 m.m. in thickness and soon 

 become so brittle and so badly cracked as to 

 be unfit for finer uses. Such inferior cork, suit- 

 able only for fuel, packing, fish-net floats, rustic 

 work in conservatories and the like, is all the 

 tree ever produces if left undisturbed. But in 

 cidtivation, when the trees are from fifteen to 

 twenty years old, all of this ' virgin cork,' as 

 it is called, is cut away, great care being taken 

 not to injure the tender part within, known as 

 the ' cork mother,' because it includes the 

 cambium. The efiect of this operation upon the 

 tree is in every way beneficial. Henceforth the 

 cork produced is more abundant, softer and 

 more homogeneous ; the breathing channels are 

 farther apart ; and the cracks become far less 

 troublesome. For a century and a half, or even 

 longer, at intervals of eight to fifteen years, 

 slabs of fine cork 5 to 20 cm. thick are peeled 

 from the trunk. The harvesting takes place in 

 summer when the inner bark adheres most 

 firmly to the wood. After being stripped from 



