Lighthouse Structures

Eddystone (Winstanley's Tower).—The Eddystone rocks, which lie about 14 m. off Plymouth, are fully exposed to south western seas. Four towers have been constructed on the reef which is submerged at high-water spring tides. The first light house (fig. 2a) was polygonal in plan and highly ornamented with galleries and projections which offered considerable obstruc tion to the sea stroke. The work was begun by Henry Winstanley, a gentleman of Essex, in 1695 and finished in 1698. In the fol lowing year, in consequence of damage by storms, the tower was increased in diameter from 16 ft. to 24 ft. by the addition of an outer ring of masonry and made solid to a height of 20 ft. above the rock, the tower being raised from So ft. to nearly 120 ft. This work was completed in 170o. The lower part of the structure appears to have been of stone, the upper part and lantern of timber. During the great storm of Nov. 20, 1703, the tower was swept away, those in it at the time, including the builder, being drowned.

Eddystone (Rudyerd's Tower).—This lighthouse was begun in 1706 and completed in 1709 (see fig. 2b). The structure consisted principally of oak timbers securely bolted and clamped together, the lower part being filled in solid with stone to add weight to the building. The simplicity of the design and the absence of pro jections from the outer face rendered the tower very suitable to withstand the onslaught of the waves, but the lighthouse was destroyed by fire in 1755.

Eddystone (Smeaton's Tower).—This famous work, which con sisted entirely of stone, was begun in 1756, the light being first exhibited in 1759 (see fig. 2c). John Smeaton was the first en gineer to use dove-tailed joints for the stones in a lighthouse structure. The stones, which averaged 1 ton in weight, were fastened to each other by means of dove-tailed vertical joint faces, oak key wedges, and by oak tree-nails wedged top and bot tom, extending vertically from every course into the stones beneath it. During the 19th century the tower was strengthened on two occasions until in 1877, owing partly to the undermining of the rock on which the tower was built and the insufficient height of the structure, the Corporation of Trinity House determined on the erection of a new lighthouse in place of it.

Eddystone (. I. N. Douglass' Tower).—The site selected for the new Eddystone tower (fig. 2d) is 120 ft. S.S.E. from Smeaton's lighthouse, where a suitable foundation was found, although a considerable section of the lower courses had to be laid below the level of low water. The base is vertical, 44 ft. in diameter, and

all the stones are dove-tailed, both horizontally and vertically, on all joint faces, those of the foundation course being secured to the rock by Muntz metal bolts. The lantern is a cylindrical helically-framed structure with domed roof, gun-metal astragals and cast-iron pedestal. The optical apparatus in this lighthouse consists of two superimposed tiers of refracting lens panels. The burners originally fitted in Eddystone tower were of 6-wick pattern, but these were replaced in 1904 by incandescent oil vapour burners. At the time of the completion of the lighthouse two bells, weighing 2 tons each and struck by mechanical power, were installed for fog-signalling purposes; these have since been replaced by an explosive gun-cotton fog signal. The work of pre paring the foundation was begun on July 17, 1878, and the light was first exhibited on May 18, 1882.' The upper portion of Smeaton's tower was removed on completion of the new light house and re-erected on Plymouth Hoe, where it replaced an old Trinity House sea mark. One of the principal features in the design of the new Eddystone lighthouse tower is the solid vertical base. Heavy seas are immediately broken up or reflected by it, spray alone rising to the height of the lantern gallery. The shock to which the gallery cornice of the old tower was exposed was so great that stones were sometimes lifted from their beds. Its suc cessor presents another point of dissimilarity from Smeaton's structure, in that the stones forming the floors consist of single corbels built into the wall instead of stone arches the thrust of which, in the earlier tower, was taken by the walls strengthened by building in chains in the form of hoops. The system of con structing corbelled stone floors was first adopted by R. Stevenson in the Bell Rock lighthouse.

Bell Rock.—The Bell Rock tower (fig. 3a), which lies 12 m. off the coast of Forfarshire, stands on an exposed reef, dry at low water and submerged to a depth of about 16 ft. at high water of spring tides. The rock is of hard sandstone. The lighthouse was constructed by R. Stevenson in 1807-11.

Skerryvore.—The Skerryvore Rocks, 12 m. off the island of Tyree in Argyllshire, are wholly open to the Atlantic. The tower, 15o ft. in height and designed by Alan Stevenson, was begun in 1838 and finished in Bishop Rock.—The lighthouse on the Bishop Rock,' the westernmost landfall rock of the Scilly Islands, occupies perhaps 'Proc. Inst. C.E. vol. LXXV. (1883).