GENERAL METHODS 141 



horizontal sections. The interval between the 

 joints (or " disjoints," rather) depends upon 

 the amount of " give " in the trunk. Near the 

 base of a tree a foot and a half is sufficiently short. 

 Farther up, the sections should be smaller. One 

 sometimes sees complicated fillings which are di- 

 vided into sections of only four or five inches. 

 The necessity for such ample provision for cracks 

 usually indicates that the limitations of the use- 

 fulness of concrete have been exceeded. The di- 

 visions are produced by leveling off the top of the 

 concrete as the filling is being built up, and spread- 

 ing a sheet of paper over the level surface before 

 continuing the filling. Newspaper does very well 

 for this purpose, and has the advantage over 

 heavier kinds that it offers no resistance to the 

 trowel in cutting down 

 the face of the filling. cambium 



Thick tarred roofing ,-^^^^H^__^ 

 paper has its advocates, 

 however, their theory 

 being that it gives the 

 filling some elasticity un- 



rlpr rnmnrpQsinn ^he concrete filling must be 



der compression. ^ ^p^ -^^^^ t,^,^^ ^1,^ ^^^. 



After the filling is bium 

 completed, the next thing 



to attend to is its outer surface and conformation. 

 At the edges the concrete should meet the wood 

 just below the line of the cambium. The distance 



