INSTITUTION OF CIVIL ENGINEERS. SESSION 1669-70. March 1, 1870. CHARLES B. VIGNOLES, F.R.S., President, in the Chair. The following Candidates were balloted for and duly elected :- HORATIOBROTHERS, RICHARD SPELMAN CULLEY, JOHN GWYNNE, ROBERTHANDCOCK, SAMUEL EEEFER, CHARLES MARTIN, B.A., WILLIAMMILLS, JAMESPRICE, EDWARD JAMES BEED, C.B., and CLIFFORD WIGRAM,Members as : JOHNGEORGE CRAMPTON,HENRY JAMESGALTON, B.A., HENRYJAMES BURFORD HANCOCK, GEORGE HODSON,HENRY JOLL, WILLIAM GEORGE LAWS,RICHARD LONG- LANDS, JOHNMARSHMAN, WILLIAM MORRIS,WILLIAM POWELL, Major FRANCISIGNACIO RICKARD, Captain FREDERICKSMITH STANTON,R.E., and GEORGEHUNTER TAIT, as Associates. No. 1,268.-“ The Wolf Rock Lighthouse.”’ By JAMESNICBOLAS DOUGLASS,M. Inst. C.E. BEFOREentering upon a description of the work which forms the subject of this Paper, it is desirable to notice briefly some others which have been, fromtime to time, executed inits immediate neighbourhood, and with which it is intimately connected. In consequence of applications, from the foreignand coasting trades navigating the English and St. George’s channels, for lights and beacons to mark the dangers of the coast near the Land‘s End, 1 The discussion upon this Paper occupied portions of two evenings, but an ab8trar.t of the whole is given consecutively. L1869-70. 11. N.S.] B Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 2 THE WOLF ROCK LIGHTHOUSE. alighthouse on the Longships Rock, and beacons on the Wolf and Rundlestone were erected under licence granted to theHonour- able Corporation of Trinity House in 1795. In the year 1841, a light-vessel was moored by the same authority off the Sevenstones Rocks, nearly midway between the Land's End and Scilly, in 40 fathoms of water. These were all works of considerable difficulty ; and the lattermay fairly be considered as the boldest undertaking up to t,hat datewith a floating light. The group of rocks included under the name of Longships, lie about 1 mile westward of the Land's End, and 72 miles N.E. from the Wolf. They are composed partly of killas and partly of granite ; the division running through the eastern part of the lighthouse rock, in a.north-easterly and south- westerly direction. The Longships lighthouse is a granite st'ructure, from which is exhibited a catoptric fixed light, and it has rendered good service to themariner; but, owing tothe terrific seas to which it is exposed, the lantern, with its centre at an elevation of 79 feet above high water of spring tides, is so much under wat'er during stormy weather, that the character of the light cannot be determinedwith certainty. It is not considered safe to raise the present tower to a sufficient height torender thelantern free from the heaviest seas; it has therefore been determined to erect in its stead a granite column 110 feet high, surmounted by a first-orderdioptric light,and which was commenced last year. The apparatus to be installed therein will admit of an arrangement being carried out for marking by sections of red light the dangers of the Rundlestone Rock and its surrounding shoals to the sont'h- ward, andt'he Brissons Rocks tothe northward. The Rundle- stone lies S. by E. 2 E., at a distance of 4 miles from the,Longships, and is 3 of a mile from the shore. It is about 17 feet 9 inches in lenghl, 8 feet 9 inches in breadth at the level of low water of spring tides, and the highest part is 8 feet 3 inches above the same level ; but the only available space for the base of a beacon is a portion of the top of the rock, 4 feet 4 inches long by 4 feet broad, at a level of 7 feet above low-water spring tides. The rock,com- posed of hardgrey granite, forms part of a dangerous group of shoals, and is the only portion visible above low water of spring tides. The beacons, referred to as having been erected on the Wolf and the Rundlestone Rocks in 1795, were merely bare poles of wroughtiron, about 4 inches in diameter, sunk into the rock andrun in with lead. That on the Wolf was about 20 feet in height, and was supported by six wrought-iron stays. The beacon on the Rundlestone was not so high, as stays could not be used, owing tothe smallsize of the rock. Both of these weresoon carried away by the sea. In addition to the beacon on t'he R,uudle- stone, t,he position of the rock was indicated by day by two marks of rubble, masonry, erected on the land, at a distance of' 1 mile. Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. THE WOLF ROCK LIGHTHOUSE. 3 These are 2204 feet apart, and when brought in line they lead over thecentre of the rock. The secondbeacon placed on the Rundlestone, shown on Plate 4, was designed by thelate Mr. James Walker (Past-PresidentInst. C.E.), theEngineer to the Honourable Corporation of Trinity House. It was erected duringthe years1841-3, under the direction of the Author's father, whowas Superintending Engineer to theTrinity House. The work was one of great difficulty and danger to those employed, owing to the small dimensions of the rock, and the difficulty of landing, which could only be accomplished atspring tides; and then the sea was seldom smooth enough to admit of a footing on the rock, as a strong tide runs to the westward during the whole of the time that t'hesummit is nncovered. The beacon was designed with a globe 6 feet indiameter; but it fort,unately happened that after the mast wasfixed, and before the globe could be attached, the most violent storm occurred that had been experienced duringthe progress of the work, when heavy seas were observed from the shore to completely submerge the top of the mast. The globe was, therefore, with the sanction of the Trinity House, reduced to a diameter of 4 feet 3 inches. The beaconwas compIeted on the27th June, 1843, and withstood the storms of the succeeding winter;but during a galein October of the following year, the wrought-iron mast of 6 inches in diameter was broken off at about 2 feet above the socket. In the month of January following, and before any repairs could be effected, a vessel struckthe beacon, and carried off thestump and a portion of the cylinder into which the mast had been stepped. The vessel, with a hole in her bottom, fortunately suc- ceeded in getting into the portof Hayle. Duringthe next summer the beaconwas reinstated by the Author'sfather, inthe manner shown on Plate 4, the globe being further reduced to a diamet'er of 3 feet. Soon after the completion of the work, a vesselwas observed to strike the beacon, but without doing it any damage, although several of her timbers were driven in, proving that the blow was not a trifling one. The mast, as thus reinstated, withstood the gales of several winters, butduring a stormin 1854 the upper portion of the beacon was carried away ; and when an exanlination could be made, it was found that the cone remained firmly attached to the rock, but that, both sides of the connecting flange at the top of the cone- jacket were broken off. In the spring of 1856, the Author was instructed by 'the late Mr. James Walker, to superintend the reinstatement of the beacon, which he succeeded in completing by the 30th June; but during a severe storm, in the following De- cember, the Enndlestone beaconwas once more entirely swept away, the holding-down bolts and mast, being broken off atthe B2 Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 4 THE WOLF ROCK LIGHTHOUSE. surface of the rock. The dangers of the Rundlestonehave since been marked by a bell buoy, designed by the Author, and shown onPlate 4. The bell, weighing 3 cwt., is fixed on a wronght- iron standattached to the deck, and is rung by four long pendulum-clappers, which are Y shaped, and thus have two points of suspension, rendering unnecessary the use of the ordinary guides. The length of swing is limited by india-rubber buffers, attached to the ironplate surrounding the superstructure, and on which the name of the station is painted. The buoy is constructed with a central water-tight compartment, large enough to float it, in the event of a vessel fouling and driving in the outerplating. A second water-tight compartment is formed at the bottom, which is used for water-ballast in cases where the buoy may be required to be placed in shallow water. The weight of the buoy complete is 65 cwt., and its cost about g185. Thatat the Rundlestone is moored with 32 fathoms of long-link mooring-chain and a 24-cwt. sinker ; 16 fathoms of the chain at the lower end is of 14-inch iron, and the remainder, or upper part, of l-inch. It is moored in 16 fat'homs of water, S.W. 6 W. from the rock, at a distance of 16 cable, on a rocky bottom and in a strong tideway. It is found to ride well, and to ring efficiently in all statesof the weather. Having thusbriefly referred to theprevious labours of the Trinity House near the Wolf Bock, the Author proceeds to describe the later and more diflicult work which is t'he subject of this Paper. The Wolf Bock, shown in plan and section on Plate 3, is situated in latitude 49" 56' 41" N., and longitude 5' 48' 30" W.