GENERAL METHODS 151 



penny nails, some fairly heavy wire, and the 

 necessary tools, such as hammer, gouge, mallet, 

 and pliers. 



The preparation of the cavity for an asphalt 

 briquette filling is not essentially unlike the prep- 

 aration for a filling of concrete. Th? decay must 

 all come out, of course, in either case. 



For concrete the cavity must be wedge-shaped, 

 smaller in front than in back. For asphalt it is 

 desirable that the sides of the cavity be as near 

 perpendicular as possible to the face of the future 

 filling. There is no change in the rules as to the 

 handling of the cambium and the shaping of the 

 incision in order to facilitate the growth of the 

 callus over the filling. 



The interior must receive a dressing just as for 

 concrete. A hot mixture of asphalt and a small 

 amount of fluxing oil is the best for the purpose, 

 because it stays sticky for some time. 



Previous, however, to the application of this 

 dressing, such braces must be put in as are neces- 

 sary, and a method of reinforcing or bracing the 

 briquette wall must be decided on and provided 

 for. The different ways in which the wall can 

 be strengthened will be taken up later on. 



If the cavity is a basal one and extends below 

 the ground, the lower part up to the surface of 

 the soil, or two or three inches above it, must be 

 filled with concrete, or partly with cinders or the 



