GENERAL METHODS 157 



This back-filling should be carried up along 

 with the briquette wall, and it should be thoroughly 

 pressed or tamped into place in order to prevent 

 subsequent settling. If it is felt that these ma- 

 terials would not give a sufficiently staple backing 

 for the wall, the entire filling can be made of bri- 

 quettes, of hot asphalt-sawdust mixture, of " as- 

 phalt-staff," or of ordinary staff made of excelsior 

 and plaster of Paris. 



In large cavities it is well to provide for the 

 ventilation of the filling. The best way to do 

 this is to leave out a briquette near the bottom of 

 the wall and another near the top. The holes 

 thus formed must be provided with a netting to 

 keep the filling in and insects out. The face of 

 the wall for an inch or two around the opening 

 can be painted with hot asphalt and a piece of 

 copper or brass netting can be pressed against the 

 opening and held there until the hardening asphalt 

 cements it in place. 



The surface of a filling made in accordance 

 with these specifications for the asphalt-wood 

 briquette system is likely to be rather irregular, 

 but it is not likely to be irregular enough to inter- 

 fere with the growth of the calluses ; yet it may be 

 desirable, from the esthetic standpoint, to make 

 it smoother. It is not difficult, with a broad, 

 sharp chisel or gouge, frequently dipped in oil, 

 to cut away the corners of projecting briquettes. 



