168 MASS. EXPERIMENT STATION BULLETIN 170. 



one or two links are placed in the rod, as is sometimes done, this dif- 

 ficulty is of course obviated to some extent. 



Galvanized stranded guy wire or cables, such as are employed by 

 public-service corporations for anchoring their poles, are superior to 

 either chains or rods for holding in place defective limbs and branches, 

 and are far more pleasing to the eye. These wire cables may be obtained 

 in various sizes and are much cheaper and stronger than chains. Their 

 tensile strength varies according to size and quality from a few thousand 

 to several thousand pounds, but the more flexible cables are best suited 



to this work. A chain is as 



strong as its weakest link or 



member, wliich sometimes 



may be very weak, whereas 



a stranded wire cable is much 



more homogeneous in its con- 

 struction and less likely to 



break. The strain which it 



is necessary to overcome in 



swaying trees is often very 



great, and we have known 



many chains to break when 



the links were composed of 



three-eighths or five-eighths 



inch iron. Wire cables and 



chains are usually used with 



eyebolts, provided with washer 



and nuts, but the eyebolt 



often constitutes the weakest 



feature. It is therefore im- 

 portant that only the best 

 quality of iron be used in the construction of eyebolts. Moreover, work 

 of this nature demands skillful blacksmithing. 



When stranded cables are used the eyebolt method is sometimes dis- 

 pensed with. In tliis case the wire passes thi-ough a hole in the tree and 

 around an embedded piece of iron. The wire method is also valuable in 

 temporarily rendering safe weak or dangerous limbs, and in anchoring 

 more or less decrepit trees to strong supports. 



Most of the chaining, bolting, etc., observed in trees follows extremely 

 poor mechanical principles. *The chains or bolts are often too small, and 

 are seldom placed advantageously as regards leverage, the majority 

 being placed too low or too near the crotch of the tree, thus requiring 

 too much strain to be overcome. Where large limbs are involved, most 

 eyebolts should be 1 inch in diameter and extend tlirough the tree, these 

 being supplied with a 3 or 4 inch washer and nut. The practice of screwing 

 eyebolts or hooks into a tree for a short distance for the purpose of attach- 

 ing a chain is bad, since they may be pulled out or broken off with the 



Fig. 29. — Showing com- 

 bination of bolting and 

 banding method which 

 caused girdling to the 

 tree. 



FIG. 30. — Illustrat- 

 ing the combination 

 banding and bolt- 

 ing method. It is 

 extremely faulty in 

 all respects. 



