[Footnote 5: Lines written by Sir Walter Scott in the Album of the Bell-Rock Lighthouse, when he visited it in 1814.] CHAPTER VIII. LIGHTHOUSES ON SAND AND CAST-IRON LIGHTHOUSES. Floating Lights--Objections to--Mitchell’s Screw-moorings-- Experiments on the Maplin Sand--Foundation--Erection of Screw-pile Lighthouse--Details of the Wyre Lighthouse--Proposed Lighthouse on the Goodwin Sands--Metallic Lighthouses--Advantages of Metal over Stone--Details of Cast-iron Lighthouse at Morant Point, Jamaica. Those dangerous approaches to a coast which, from the nature of the soil, have not till very lately admitted of the erection of a permanent lighthouse, are usually indicated to the navigator by floating lights; but these being nothing more than large lanterns suspended in the rigging of a vessel, necessarily possess but feeble illuminating power. This power is still further diminished in a gale of wind, when it is most wanted, by the pitching and floundering about of the vessel: every now and then she is submerged in the trough of the sea, covered with spray and drift, or, what is most to be dreaded, she is liable to be blown away from her moorings; an accident which has been productive of the most disastrous consequences to life and property. The details already given will convey some notion of the difficulty and danger of planting a lighthouse on the solid rock in a stormy sea; we may naturally suppose that this difficulty and danger must be enormously increased in erecting a permanent residence on the shifting sands. Such, however, is by no means the case; one of the recent triumphs of engineering has proved that it is not always folly to build a house upon the sand. This remarkable result has been accomplished chiefly by means of Mitchell’s screw-mooring, an instrument which consists essentially of an enormous cast-iron screw of about one turn and a half, having a hollow cylindrical centre; a wrought-iron spindle passes through the cylindrical socket; it is somewhat tapering in form, and when driven up tight is fixed thereto by a forelock passing through both; it is formed with a square head to receive the key for screwing it into the ground. It is also furnished with a collar of wrought iron fitted so as to turn freely on the upper part of the shaft of the spindle below the collar.