Engineering Wonders of the World
Volume I

THE STORY OF THE LIGHTHOUSE. 373 Fig. 7.—LINTEL STONES OF FLOORS OF BELL ROCK LIGHTHOUSE. Fig. 8.—ARCHED FLOORS IN SMEATON’S EDDYSTONE LIGHTHOUSE, WITH CHAINS EMBEDDED IN WALLS TO TAKE THE OUTWARD THRUST. Fig. 9.—section of skerryvore lighthouse (A. Stevenson, 1843). Fig. 10.---------JOINTING OF MASONRY IN SKERRYVORE LIGHTHOUSE. Fig. 12.—JOINTING OF MASONRY IN DHU HEARTACH LIGHTHOUSE. evident in Smeaton’s tower, but not to an equal extent. Attention may here be drawn to the fact that a masonry lighthouse requires no fixing to the rock on which it is built, because friction between the materials is quite sufficient to guard against any lateral displacement. It is very important, however, that the bottom of the tower should rest upon horizontal surfaces, either cut in the form of steps, as in Fig. 5; toothed, as in Fig. 3 ; or flat, as in Fig. 9. The object is to bring the weight of the structure upon the rock in a truly vertical direction, and to prevent the existence of any outward thrust. During the work of con- struction it is necessary to connect the stones to each other and to the rock in order to obviate the risk of any of them being washed away before enough weight has been super- imposed to give security. In stormy seas this risk is always present, and during the building of the Bell Rock