184 MASS. EXPERIMENT STATION BULLETIN 170. 



FIG. 55. Section of tree with 

 cavity illustrating wire and 

 elastic cement method of 

 covering opening. C, elastic 

 cement; W, wire mesh; I, 

 iron re-enforcements. 



Another method of treating tree cavities with the use of asphalt has 

 been devised and described by Elbert Peets. This consists of using brickets 

 or units composed of asphaHum and excel- 

 sior. These brickets are employed as a 

 covering to the outer surface of the cavity, 

 and are cemented together with asphaltum. 

 The brickets are secured to the side of the 

 cavity opening by spikes, a^nd are held in 

 place by iron re-enforcements, the portion 

 of the cavity back of the brickets being filled 

 with sawdust, cinders or other material. 

 An especially commendable feature of this 

 method is the unit system employed, and 

 the adaptability of the material to the move- 

 ments of trees. On the other hand, asphal- 

 tum is not a convenient substance to use 

 because it has to be heated. The same objec- 

 tions to completely filling a cavity apply 



also to asphaltum, although with the use of this 

 material such a practice may not always be 

 necessary. 



Wooden Block Method. This method of seal- 

 ing cavities (invented by the writer) has been in 

 use only recently. It consists in the use of chem- 

 ically treated wooden blocks to cover the open- 

 ing of the cavities, and makes filling unnecessary. 

 The blocks are of different sizes. Each one 

 constitutes a homogeneous structural unit com- 

 posed of various cellular elements, similar to 

 those in trees. With this method, as in others, 

 the cavities are cleaned and treated antiseptically, 

 the blocks being used simply to cover the orifice 

 of the cavity and to direct the growth of the 

 callus or healing tissue. 



The advantage of wooden blocks for cavity 

 work consists in the fact that the blocks are 

 composed of the same type of element as found 

 in trees. The geometrical arrangement of the 

 various elements, as well as their chemical com- 

 position and molecular structure, is similar; 

 moreover, the physical properties rigidity, 

 elasticity, etc. are practically identical. The 

 various movements in the cavities of trees re- 

 sulting from variation in temperature, moisture, 

 barometrical influence, etc., may be better conformed to by the use of 

 this material than by any other yet employed for the cavity treatment. 



FIG. 56. Chemically 

 treated wooden block 

 covering of cavity open- 

 ing, with back re-en- 

 forcements of wood. 

 The normal growth of 

 the callus is not dis- 

 turbed. (After J. A. 

 Davis, City Forester, 

 Springfield.) 



