166 PRINCIPLES AND PRACTICE OF PRUNING 



In the preparation of cavities to be filled with sawdust and 

 asphaltum, as with cement, or to be rendered antiseptic without fill- 

 ing, it is recommended that the decayed parts be removed to sound 

 wood. This involves removal of all soft and rotten material ; some- 

 what deeper cutting away seems advisable in shade trees than in 

 fruit trees. It is further recommended that the interior surfaces 

 be rendered sterile by applications of corrosive sublimate, carbo- 

 lineum or kerosene. It is not advisable to use creosote, because it 

 is too penetrating for use next to living parts. The thoroughness 

 with which the work of removal and disinfection is done will very 

 largely determine the success of the fillings made. 



In case of very large cavities filled with asphaltum-sawdust mix- 

 ture, it may be desirable to use an outer screen of close wire netting 

 or of poultry netting. In any case the outer line of the filling will 

 be kept more uniform by some surface, as of oil-coated wood or 

 metal, against which pressure is exerted as the filling is made. 

 Finally, the irregular and general surface of the filling may be 

 coated properly and successfully with gas tar or liquid asphaltum ; 

 either of these is a proper dressing for any border surfaces that 

 may have been cut to secure contact with the filling. 



It is to be noted that the solid asphaltum referred to in materials 

 is that derived from the refining of petroleum with an asphaltum 

 base. It can be stored and shipped in iron drums. In recent years 

 it has been used for filling the interstices of street pavements, and 

 for many other purposes. 



