THE FKENCH SYSTEM OE PRUNING. 283 



say in favour of coal-tar, it is, after all, one of the very 

 worst appliances for preserving wood and preventing 

 decay. I have made several experiments with it, and 

 bestowed much attention to its preservative properties, 

 and if anything I am more and more confirmed in the 

 fact that coal-tar should not be used for the purpose 

 here recommended, but vegetable-tar should be used 

 instead, or creosote, which is extensively employed for 

 the preservation of railway sleepers ; and in the ab- 

 sence of these, oil of any kind, turpentine, or alum 

 in solution. It is also to be hoped no one will venture 

 to cut off from the bole of an old tree a limb of any 

 kind, under the impression that the wound can be 

 healed and the tree left in as good a state as before. 

 Let the advice, repeatedly tendered throughout this 

 book, be listened to, not to prune any branch from a 

 tree unless absolutely necessary and cannot be avoided ; 

 and withal to rest fully satisfied that in any case the 

 tree, as a timber tree, is rather injured than benefited 

 by the practice of pruning large limbs or heavy 

 branches. 



