Telegraphy, by W.H. Preece and J. Sivewright. 3rd [Sic] Ed

Telegraphy, by W.H. Preece and J. Sivewright. 3rd [Sic] Ed

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1884 edition. Excerpt: ...184. The external applications are: --a. Seasoning.--The poles when felled are cleared of their branches, the bark is stripped off, and the knots shaved down; they are then sheltered alike from the sun and the rain, and stacked in such a manner that the air is allowed to circulate very freely amongst them. In this way the evaporation of the sap is promoted. To get rid of the sap and the inherent germs of decay, timber has been kept immersed for a time in salt water; artificial drying in a hot-air chamber has also been resorted to, but the most perfect seasoning is that which is effected simply by exposure to free currents of air. b. Charring and Tarring.--This process consists in gently roasting the butt end of the pole, after having been well seasoned, for a length of about six feet, over a slow fire, and removing it immediately the surface becomes well blackened without being burnt. The object is to expel whatever sap remains, . to kill whatever animal or vegetable life may be present, to prevent absorption of moisture, when the pole is planted, by destroying the external pores of the wood, and substituting an impervious covering in their place, and finally to surround that portion most liable to decay with a powerful antiseptic in the shape of carbon. The bottom of the pole, as well as the portion which has been charred, should then be well coated with a mixture of three parts of Stockholm tar to seven parts of gas tar well boiled, and three parts of slaked lime added, care being taken to scrape off, before the tar is put on, any part of the wood which may have been burnt during the process of charring. The tar assists in more effectually accomplishing the object of the charring, and by being applied to the bottom of the pole prevents.show more

Product details

  • Paperback | 86 pages
  • 189 x 246 x 5mm | 168g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236784669
  • 9781236784667