SELECTING THE TYPE Of 1 CONSTRUCTION 27 



they are not usually depended upon for regular service they may be very cheaply con- 

 structed. Often emergency wire laid only during the fire season is employed for this 

 purpose. 



These lines shou'ld, if possible, 'be entirely isolated from the regular lines except 

 when in use, unless they are of standard construction. They can generally be rather 

 easily maintained because they are short and have occupied stations at each end. 

 Whenever possible one such station should be a lookout, thus affording an alternative 

 route to the lookout station and ensuring continuous switching service at one end, at 

 least, of the closing line during the fire season. 



Section 31 Secondary Strategic Points 



Needless to say, there are many points within or adjacent to a forest area other 

 than headquarters of the protection staff which may advantageously be included in the 

 system of communication. These are usually included in the general term, " strategic 

 points," and include logging, mining, construction, and other similar camps, local 

 settlements, stores, summer resorts, power stations, saw-mills, boat landings, stage 

 stations, ranches, and, in fact, any point where either labour or supplies may be secured 

 in an emergency, or from which reports of fires burning in or adjacent GO the forest 

 may be sent. As far as is practicable, the main system should reach these points. 

 Those not so connected may subsequently be reached by spurs if desirable. 



CHAPTER V 



SELECTING THE TYPE OF CONSTRUCTION 



FOT forest-protection purposes two principal types of construction have been 

 employed. These are pole lines and tree lines. Pole-line construction, as used on forest 

 lines, differs in no material aspect from ordinary rural-line methods. Several simple 

 manuals of construction have been published setting forth these methods in detail 

 but for the purpose of making this manual of communication complete a description 

 of these methods will be included. 



Section 32 Pole-line Construction 



Briefly stated a pole line consists of poles of a specified length set firmly in the 

 ground at specified, uniform intervals and bearing glass or porcelain insulators to 

 which the line wire is rigidly attached by short tie wires. Pole lines are as straight 

 as possible. On curves the wire is always placed on the convex side and the sag 

 between poles is only sufficient to allow for the normal contraction of the wire with 

 changes of temperature. 



Section 33 Tree-line Construction 



Tree-line construction is radically different from pole-line construction. As a 

 matter of /act, in most important aspects tree lines are the exact opposite of pole 

 lines. It is important that this be noted, especially when employing linemen who 

 have had previous experience in the building of pole lines. Such experience always 

 predisposes them to follow methods that produce very faulty tree lines, and sucji men 

 must generally be more carefully supervised when first put on tree-line work than 

 men who have had no previous experience whatever. 



Briefly stated, tree lines consist of trees of varying sizes, at varying but as nearly 

 as possible equal distances apart, trimmed of branches on one side to a specified 



