108 



STEEET AND HIGHWAY PLANTING. 



groove is cut to hold the cement. The surfaces of the cavities are 

 often studded with nails to hold the filling tightly in place. Small 

 cavities are filled with Portland cement, but the larger openings need 

 the addition of broken stone and brick to form a firm foundation, and 

 in cases where the excavations are extensive the use of steel rods is 

 desirable. Often woven wire of varying size mesh is put into the cavity. 

 In filling openings of considerable size the work can be built up 

 slowly, using an artificial framework to mould the front surface until 

 the mixture sets. The cement should be mixed rather thin, so that when 

 tamped it will settle evenly and thoroughly into all the cracks. In mak- 

 ing the framework for the front of the mould and in filling any cavity 

 (Fig. 50), it is essential that the outer surface of the new concrete 

 filling does not come outside of the inner surface of the bark. If it 



Fig. 51. 



does not, the growing layers just under the bark will continue to grow, 

 and in many cases will completely cover openings of some size. If it 

 does exceed the growing level, the new wood in growing will set up a 

 pressure which will ultimately crack the filling and make it fall out, 

 In order to be sure of a clean, regular surface, it is well to trim an even 

 margin all about the opening, painting the exposed surface with some 

 coal tar preparation. 



Oftentimes fine specimens will be split in a crotch between two of the 

 larger limbs. The common practice of putting an iron band about the 

 two limbs results in the inevitable girdling of the tree, unless the bands 

 are of such a width that the tree can burst them. The more simple 

 and correct method is illustrated in Fig. 51. In time the wood will 

 grow about the nuts, which are sunk in the cement ; or a bolt may be run 

 directly through the limbs, and no chain will be needed. 



