SHADE TREES. 



179 



etc., have been used freely in numerous ways for re-enforcing. When 

 the cavity has no " shoulders" to hold the cement in place, spikes 

 driven into the wood are effective in anchoring the cement, and we have 

 observed such fillings to remain undisturbed for many years. 



Any filling substance or covering of a cavity should always come flush 

 with the exterior of the wood. For this purpose it is best to cut the bark 

 back as little as possible to expose the edge of the wood to view. Special 

 grooves cut in the wood of the cavity just anterior to the outer edge of 

 the wood have been used with the idea of directing the flow of surface 

 water which may enter the cavity, or that arising from the interior caused 

 by bleeding, but these grooves have not 

 proved of practical value. A V-shaped 

 groove cut in the edges of the cement 

 before hardening, filled with elastic cement 

 to prevent water from entering, is some- 

 times used. As there is always more or 

 less separation of the cement from the 

 wood after setting or hardening use has 

 been made of thick elastic substances to 

 cover the surface of the cavity to make 

 the contact more complete. 



Sectional Concrete Fillings, The writer 

 first experimented with sectional concrete 

 fillings in 1902 and 1903, and has at dif- 

 ferent times since suggested this method 

 of filling cavities to those seeking to avoid 

 cracking of the cement where considerable 

 movement exists. In our original experi- 

 ments the. cement was laid in sections, each 

 section being allowed to become set or 

 hardened before another was put on. The 

 sections were further separated from one 

 another by the use of such substances as 

 cardboard or tarred paper, fiberoid, elastic 

 cement or wire mesh. Our idea in de- 

 veloping the use of sectional work was to eliminate cracking of the 

 cement which so commonly follows the use of this substance, and the 

 purpose of using more or less elastic substances between the sections was 

 to form a bed for each section or independent unit to move upon dur- 

 ing swaying without causing chipping of the edges of the sectional blocks. 

 The sectional method of filling has been employed quite extensively within 

 the last six years, and at present it constitutes the best method of 

 employing concrete cement in tree cavities. 



In some of this work the sections are bolted to the tree, thus restricting 

 independent movement to a certain extent by anchoring the sections. 

 In consequence of this anchoring the sections load the tree with weight, 



FIG. 48. Stump growth of white 

 oak with cavity cleaned and 

 treated with creosote and filled 

 with cement. Edge of cavity 

 effectively sealed with elastic 

 cement. 



