34 



Mr. John Davie, who has had large experience in filling trees with 

 cement, in many of his fillings makes use of large iron bars. These 

 are securely tied to the sides of the cavity for the purpose of holding 

 the cement filling in place. 



Occasionally a cavity is not entirely filled with cement, but a brick 

 wall is constructed and the surface plastered with cement even with 

 the wood, and in other cases the cavities are dug out, treated anti- 

 septically, and covered with tin put on flush with the surface of the 

 wood. Mr. H. L. Frost, of Arlington, has done some excellent work 

 in tinning over cavities. 



Fig. 14. Showing the evolution of a cavity and method of treating the same, a, long 

 stub left from pruning, b, beginning of decay. c, more advanced stage, d, cavity formed 

 in the wood, e, longitudinal S( ction of the trunk showing cavity, f, cavity cleaned out 

 and filled with cement. 



JJoth the cenier.t and tin methods have their defects. In the tin- 

 ning method, changes in temperature may cause the tacks to become 

 loosened, displacing the tin, in which case the callus grows under 

 the tin, displacing it still more and defeating the object of the treat- 

 ment. On the other hand, the cement is likely to crack on the sur- 

 face and contract from the wood after drying, and in some instances 

 adds too much weight to be supported when limbs are filled. This 

 may be obviated by filling with some lighter substance or by tinning, 

 and in some cases the weight has been supported in part by rods 

 extendine; from the trunk into the limbs and imbedded in the cement. 



