“To bolt a tree correctly is comparatively inexpensive. The safest method consists in passing a strong bolt through a hole bored in the branch for this purpose, and fastening it on the outside by means of a washer and a nut. Generally the washer has been placed against the bark and the nut then holds it in place. A better method of bolting, and one which insures a neat appearance of the branch in addition to serving as the most certain safeguard against the entrance of disease, is to counter-sink the nut in the bark and imbed it in portland cement. The hole for the sinking of the nut and washer is thickly coated with lead paint and then with a layer of cement, on which are placed the nut and washer, both of which are then imbedded in cement. If the outer surface of the nut be flush with the plane of the bark, within a few years it will be covered by the growing tissue.
“The inner ends of the rods in the two branches may be connected by a rod or chain. The preference for the chain over the rod attachment is based on the compressive and tensile stresses which come on the connection during wind storms. Rod connections are preferred, however, when rigidity is required, as in unions made close to the crotch; but for tying two branches together before they have shown signs of weakening at the fork, the chain may best be used, as the point of attachment may be placed some distance from the crotch, where the flexibility factor will be important and the strain comparatively small. Elms in an advanced stage of maturity, if subjected to severe climatic conditions, often show this tendency to split. These trees, especially, should be carefully inspected and means taken to preserve them, by bolting if necessary.”
The illustrations, Figs. 164-173, are self-explanatory, and show poor practice and good practice in the care of trees.
