Elementary telegraphy : a manual for students; written specially to meet the requirements of the ordinary grade of the subject as published in the syllabus of the city and guilds of London Institute (1910)
Pendry, H. W. (Henry Walter) · London ; New York : Whittaker & Co. · leaf 147
wires can therefore be safelysuspended at once. Earth borers (Fig. 114) are devised to reduce the laboTxrand cost of pole setting. In lightand sandy soils and whereno greater depth than four feet is required these tools haveadvantages. The rotating motion conveyed by the handleheaps the earth upon… … Fio. 114.—Earth borer. TELEGRAPH LINES 137 Hamiltnv pole (Fig. 115).—This type of iron pole hasbeen specially designed for use abroad, and is constructedto combine strength and durability Avith lightness, porta-bility and simplicity of construction. The poles arecomposed of 8-feet lengths of…
Telegraph
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