248 MASS. EXPERIMENT STATION BULLETIN 170. 



transmission services, however, are at present on private property and 

 seldom interfere with trees. High-tension Hnes are afl'ected seriously 

 merely by close proximity to trees; therefore, these rights of way have 

 to include broad strips of land, which of course is expensive. 



On general principles, it is not wise to allow wires to be attached to 

 trees, although this is often done. Trolley and electric light wires are 

 frequently guyed to trees, but they are a source of 

 danger, since injury is likely to occur from the cross- 

 ing of the wires, and lightning discharges occasionally 

 pass from the wires to the tree, causing damage. It 

 is, however, often better to allow this than to allow 

 the erection of ugly poles; but proper insulation of 

 the wires should be insisted on, although ordinary 

 insulators have little effect on lightning discharges. 

 The iagbolt system in common use for guying wires 

 to trees is not the best method, for sooner or later the 

 wire and bolt become imbedded in the tree and cause 

 injury. Moreover, a direct metal connection with a 

 tree is objectionable, as has in more than one instance 

 been proved. The block system is better, although 

 it m^y not in all cases be free from objections. 

 (See Fig. 42.) In no case should a wire be allowed 

 to pass tightly around a tree, as it will girdle it in 

 time. When live wires come into contact with limbs, 

 some type of insulator should be employed similar to 

 that shown in (1), Fig. 105, of which there are various 

 types, some being quite effective in preventing injury 

 from low-voltage lines. The type shown in (2), Fig. 

 105, is cumbersome and unsightly, but is one of the 

 most effective. The principle of the porcelain and 

 dowel insulator is good, but it has a tendency to slide 

 on the wires and to become displaced. If it were 

 provided with larger dowels, and the danger of dis- 

 placement on the wires done away with, it would 

 prove much more satisfactory. 



Wires often accidentally come into contact with 

 trees by the displacement of poles, particularly on 

 curves where the strain is verj^ great, but much of tliis injury may be 

 prevented by imbedding the poles in Portland cement. It should be 

 pointed out that the necessity for guying poles to trees may be obviated 

 in this wa3^ 



Better methods of handling this vexatious question of wires and shade 

 trees should be forthcoming in the future, and even at the present there 

 must be a compromise between the tree warden or city forester and the 

 companies as to the best method of wiring through tree belts and the 

 amount of pruning allowed. Conditions at present favor the corporations, 



Fig. 104. — Showing 

 maple tree in- 

 jured by lightning 

 discharge from 

 trolley guy wire, 

 causing death of 

 limb and lacera- 

 tion of trunk. 



