PRESERVATIVES AND MATERIALS 205 



White Lead or Zinc. The results of experi- 

 ments that have recently been carried out 

 at the New York Agricultural Experimental 

 Station would suggest that as a covering for 

 tree wounds white lead or zinc is preferable, 

 in so far as the healing is concerned, to either 

 tar, creosote, or carbolineum. An objection 

 to the use of white lead or zinc, in parks and 

 public gardens, is undoubtedly the colour, 

 which so nearly resembles that of the wood 

 that the mark of pruning, which it is often 

 necessary to hide, is not obliterated. 



Concrete Filling. In the filling of cavities 

 or hollow stems, one part of cement to four 

 parts of clean gravel will be found sufficient in 

 making the concrete. As to the method 

 adopted in mixing and filling little need be 

 said, the mason or gardener being usually well 

 up in such operations. In finishing off" the 

 filling at the entrance to a cavity, cement only 

 should be used, as this entirely excludes damp, 

 and owing to smoothness of surface allows the 

 cambium and bark to quickly heal over, at 

 least in the case of healthy trees. 



Broken Bricks. Old bricks, broken to the 



