VARIOUS TYPES OF CAVITIES 173 



while to dry. Spray it with creosote, then build 

 up a dam of moist clay, covering the crack nearly 

 to the top. The clay can be held in place by 

 boards, which are themselves held by ropes around 

 the tree. Fill the split by pouring in hot asphalt 

 through the opening at the top. An asphalt of a 

 rather low melting point, or one slightly fluxed 

 with oil, is preferable to a very hard one. The 

 asphalt must ordinarily be used clear, but if the 

 crack is a large one it may do to mix some saw- 

 dust with it. 



The braces through the split limbs and also, 

 preferably, up above, must be set in place before 

 the asphalt is poured, and then 

 tightened up after it has hard- 

 ened. It is in many cases well 

 to put in a pair of bolts through 

 the trunk at an angle with the 

 plane of fracture. 



The last form of cavity we 

 shall consider is the " chimney ^p"' %Vef "'^ *"" 

 cavity," which results from the 

 complete decay of the heartwood of a tree. It is 

 almost invariably marked by a basal opening at 

 the ground and another large opening at the top, 

 where a large limb or the top of the main trunk 

 itself, has been broken off. The hard proposition 

 connected with this type of cavity is the excava- 

 tion of the decayed wood. If the decay is di<E- 



