Bracing and Repairing Trees 161 



underside of the living bark ; in other words, the cambium 

 should be left free for expansion. Sometimes, brickbats, 

 broken small, are used instead of gravel, but for various 

 reasons concrete is preferable. The concrete surface may 

 be prevented from cracking by applying annually a coat of 

 paint, which, for appearance sake, may be of a similar 

 colour to that of the bark of the tree. 



In the case of a large tree in which the trunk is quite 

 hollow, usually with a basal and top opening, the amount 

 of cement required to fill the cavity precludes the possi- 

 bility of it being employed on the score of economy, but 

 where the hollow only extends for a comparatively short 

 distance upwards and inwards the composition is to be 

 recommended. When a large amount of material is re- 

 quired to fill a hollow stem, clean bricks broken to about 

 the size of a golf ball may be used, but they must be packed 

 firmly and the surface, wherever it comes in contact with 

 the weather, glazed over with cement in order to effectually 

 shut out dampness. Asphalt has of late years been em- 

 ployed in the filling of hollow stems, and is to be recom- 

 mended on account of its elasticity and lasting properties. 



Sometimes, the interior of a large, hollow tree stem is 

 strengthened by crossbeams of timber, any holes which 

 extend to the outside being carefully covered with sheet 

 lead or zinc so as to prevent the ingress of water. A sheet 

 of lead or zinc is, however, only a superficial remedy and 

 should be dispensed with where filling the cavity is at all 

 practicable. Lead, in some cases, is preferable to zinc for 

 covering wounds in trees, as it fits into position more readily 

 and is easily fixed. 



The treatment of hollow stems without filling the cavity 

 is in certain instances quite permissible, and can be carried 

 out at a comparatively small cost. Broadly speaking, this 

 method consists in cleaning out all decayed and decaying 

 matter, painting the interior with carbolineum or tar, and, 

 where possible, bracing the trunk from the interior by means 

 of stout crossbars of wood and covering surface holes with 

 lead, zinc or sheet copper. When a tree trunk is hollow 

 from top to bottom this method is to be recommended, and 



M 



