74 



The thinner the strip of bark shaved off, the longer 

 time any given area of bark will last and the longer 

 it takes before coming 1 round acrain to the same place. 



O cT> JT 



We will refer again to these general rules when con- 



FlGURE 27. 



Sketch showing the rolled out bark. 



a /> represents the line where the bark has been opened; in the second 



figure, the bark is rolled out; the lines a b and a' />' 



are therefore the same line of section. 



sidering the manner in which the tapping takes place 

 in practice. 



2. TAPPING SYSTEMS. 



In order to elucidate the different tapping systems, 

 it is essential to show in detail by means of diagrams 



