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POPULAR SCIENCE MONTHLY 



square, eight feet high above the eaves, and about eighteen inches more at the 

 ridge-pole. ... It is better to have the cupola open into the operating room 

 when the room is in the top story of a building, and cleats are fastened round 

 the inside, bored with a number of holes, corresponding to the number of wires 

 required. . . . The wires, after entering are led to the lightning arrester, then 

 run through the holes in the cleats, which run round the base of the cupola, to 



the ceiling of the operating room, along 

 which they are carried, on other hard 

 wood cleats, to the switchboard. . . . 

 Where the main lines are not sufficiently 

 numerous to render a cupola necessary, 

 they may be brought through a window 



in the central office. 



(Fig. 37.) The 



line wires are strung on (pony) glass in- 

 sulators, which are fitted to wooden pins, 

 driven into crossarms. These crossarms 

 are supported on poles or house-top fix- 

 tures, which should be run in trunk-routes 

 through the city or town, branch lines be- 

 ing run to any desired point. It is advan- 

 tageous to use poles wherever practicable, 

 for the following reasons : Pole lines are 

 not liable to interference from household- 

 ers, being entirely out of their control ; they 

 are much more accessible at all times, and 

 when they are out of order at all the 

 trouble is more easily located and removed; 

 the cost is generally about the same, where 

 the number of wires to be carried does not 

 exceed forty or fifty. Poles should be not 

 less than twenty- five feet long, with a diam- 

 eter of six inches at the top; and should be set five feet in the ground. Before 

 being set up, poles should be carefully stripped of the bark, and, when used in 

 cities, should be painted. It is the usual practise to place all the crossarms on 

 one side of the pole, fastening them with bolts and nuts. It is sometimes, how- 

 ever, absolutely necessary to run house-top lines. Trunk routes should then be 

 selected, and along these routes structures must be erected at an average dis- 

 tance of about three hundred feet apart. Fig. 38 represents a roof fixture, with 

 four cross-bars, each bar having glass insulators on its upper side, and ' hook ' 

 insulators on its under side, thus doubling its capacity for carrying wires. 

 Hooks being expensive, porcelain knobs may be substituted for them as an 

 economical measure. (A foot note reads: It is much better to avoid adding 

 hook or other fixtures to the lower edge of cross-bars. It is apt to bring the 

 wires too near together, and cause trouble from ' induction.' It should be done 

 only when new fixtures cannot possibly be erected.) A correct idea of a ' double 

 wall fixture' may be obtained from Fig. 3&. It is in many cases desirable to 

 use this style of fixture in preference to a roof fixture, as removing all danger 

 of causing leaks in roofs; or in cases where flat roofs are not attainable, or 

 where the point of support is necessarily a high party wall or the side wall of a 

 building. . . . Bad construction, necessitating frequent clambering over roofs, 

 while it may do no real harm to the premises, annoys owners and tenants, whost 

 condemnations and complaints soon reach the ears of others, and this is apt to 

 put stumbling-blocks in the way of securing permission for entering upon new 



