Lighthouses and Lightships; A Descriptive and Historical Account of Their Mode of Construction and Organization

Lighthouses and Lightships; A Descriptive and Historical Account of Their Mode of Construction and Organization

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1870 edition. Excerpt: ...from distant parts. The first and most embarrassing, perhaps, of the numerous questions which present themselves to the engineer when entering upon the construction of a lighthouse, are those of the height and the mass. In the days of Smeaton, when the best light in use was that of common candles, the elevation beyond a certain point could not be of any utility; while in 1835 the application of the reflector and the lens, by assisting in the extension and diffusion of the light, rendered, on the contrary, a considerable elevation both necessary and desirable. It was therefore decided that the height of the Skerryvore should be 135 feet above the highest tides, so as to command a horizon visible for a radius of eighteen miles. The diameter of the base was fixed at 42 feet, and that of the topmost story at 16 feet; consequently the masonry of the tower would be double that of the Bell Rock, and four and a half times that of the Eddystone. Another peculiarity distinguishes the Skerryvore from the Bell Rock. The sandstone of the latter is waveworn, and broken up into a thousand rugged inequalities: the action of the sea on the igneous formation of the Skerryvore has, on the contrary, communicated to it the appearance and polish of a mass of dark-coloured crystal. It is so compact and smooth that the foreman of the masons, when he landed on it, said it was like climbing up the neck of a bottle. Moreover, notwithstanding its durability, the gneiss of Skerryvore is excavated into caverns, which considerably limit the area adapted for 174 A VIOLENT STORM. building operations. One of these caverns, we are told, terminates in a narrow spherical chamber, with an upper opening; through which, from time to time, springs a bright, luminous shaft of water, more

Product details

  • Paperback | 74 pages
  • 189 x 246 x 4mm | 150g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236550846
  • 9781236550842