File:The practical telephone handbook and guide to the telephonic exchange (1906) (14569563229).jpg

Identifier: practicaltelepho00pool (find matches)
Title: The practical telephone handbook and guide to the telephonic exchange
Year: 1906 (1900s)
Authors: Poole, Joseph
Subjects: Telephone
Publisher: New York, Macmillan Co.
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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he joists and brickwork and themanhole cover frame is fitted on top of these as shown, thewhole being rendered watertight by cement. If formed undera roadway heavier joists, 5 inches by 4; inches, should be used,as shown in Figs. 387 and 388. The ducts, if of iron, areterminated in the manholes by well-rounded bell-mouthedends, so that the cables may not be injured by sharp edges. UNDERGROUND WORK 3^9 The top part of the cover is filled in to the level of the roadwith hard wood blocks (such as jarrah wood) or with othermaterial to conform, with the general construction. Obstructions.—In laying the pipes and making the man-holes obstructions are frequently met with, owing to the exist-ence of gas, water, and other mains, and much engineeringskill has to be exercised in order to avoid such obstructions.Figs. 389 and 390 show an example of this, a double manholehaving to be constructed in order to drop from a 4-foot levelin one street to a lower level in another street at right angles,
Text Appearing After Image:
Fig. 388.—Plan of Manhole under Roadway (Scale ^-~) so as to avoid obstructions in the shape of gas, water, andhydraulic mains. Concrete-Moulded Manholes.—The standard practice inAmerica is to make the manholes of concrete moulded in posi-tion by the help of temporary wooden templates or moulds.The form generally given to them is egg-shaped in plan, withflattened ends where the ducts terminate, this shape beingadopted for greater strength to resist side pressures, and alsofor cheapness of construction. The walls are moulded 8 inchesthick, and the roof is arched over. 390 PRACTICAL TELEPHONE HANDBOOK Concrete-Block Manholes.—Another method of manhole

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