1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



67 



WROUGHT IRON BEACON. 



Description of a Wroughl Iron Beacon erected at the harbour of 

 Black Rock, in Long Island Sound, in the iummer of 1843. Bv W. 

 H. Swift, Capt. Corps Topi. Engs. (From the American Journal of 

 the Franklin Institute.) 



In March, 1843, an appropriation of 10,000 dollars hnvinpr been 

 made by Congress', for rebuilding the Black Rock Beacon, the Secre- 

 tary of the Treasury applied to the Secretary of War to allow this 

 beacon to be constructed under the direction of the Chief Topogra- 

 phical Engineer, and by the orders of Colonel J. J. Abert, the work 

 was entrusted to the superintendence of Captain W. H. Swift. 



The beacon stands li mile south of the entrance to the harbour, and 

 is exposed to all winds from E.N.E.; around by the south to W.S.W.; 

 from the east it is open entirely to the rake of the sea for a distance 

 of sixty miles. 



When the first beacon was built in 1829, a large quantity of pebble 

 stone was carried in vessels to the proposed site, and there thrown into 

 tlie water around a single rock called the "Old Huncher," and upon 

 which there had been an iron spindle in former years; this rock was 

 conical in shape, about 4 ft. in diameter at top, and bare at very low 

 water. Upon this loose stone, thus deposited, the superstructure \yas 

 reared, and when the beacon was overthrown, the materials of which 

 it was composed, were, of course, added to the rubble stoiie bed, and 

 thev, in turn, became the foundation for the beacon of 1835. 



In the examination which I made of the site in June, preparatory 

 to making the final plan for the iron work, I ascertained that the stone 

 below low water, had, apparently, remained unmoved for a long time, 

 anil I subsequently found, by inquiring of Captain Wilson, the con- 

 tractor, who had repaired tlie beacon in 183(5, and who had maintained 

 it iu repair for five years, that such was the fact; while, as he stated, 

 and it was evidently true, the stones between low and high water were 

 thrown about bv the force of the sea in every gale. This was fully 

 exemplified too by the appearance which the injured part of the olil 

 beacon presented ; the base, or that part below low water, was entirely 

 undisturbed, the breach being between high and low water marks; all 

 the stones below low water remaining, as stated by Capt. Wilson, as 

 they were when the beacon was repaired in 1835. 



There being no stone of sufficient size at the old beacon into which 

 the iron shafts of the new structure could be secured, I found it ne- 

 cessary to procure elsewhere such as were suitable for the purpose, 

 and to transport them to the site, and imbed them below the line of 

 low water, in order that the sea might not disturb them after they 

 should be laid. 



Stone Foundation.— The beacon, according to the general plan 

 which I had made, and submitted to Col. Abert on the 3Uth of April 

 last, was to be elevated 36ft., and for this height I decided to give the 

 iron shafts a spread, or base, of 16ft., with an inclination towards the 

 centre of about 1 to 6. In order that there should be sufficient strength 

 in the stone to resist anv tendency there might be to fracture at the 

 holes which were to receive the feet of the shafts, I a<lopted the di- 

 mension of 20ft. as a suitable diameter fur the stone bed designed for 

 the shafts to be secured to; this dimension gave a distance of about 

 2* ft. from the centre of the shaft holes to the edge of the stone at top, 

 while at the bottom of the stone, where the strain is less, it would be 

 2 ft. The bed then is composed of 6 pieces of hammered granite, 

 2^ ft. thick ; the middle stone is round, and is 8ft. in diameter, the five 

 outer stones are 6ft. wide by about 12ft. in length, each stone weigh- 

 ing nearly 12 tons; the stones are cramped and doweled together with 

 ifin. round copper,' two at each joint, the cramps 2ft. long, and the 

 dowels 10 and 12in. long. 



The excavation which was made iu what may be called the artificial 

 island (for at low water an extent of lU5ft. from east to west, and 

 88 It. from north to south is exposed,) for the reception of the stone 

 bed is a few feet N.W.from the old beacon; it was 26ft. in diameter, 

 aud 3ft. below or(ii7mry low water. When the excavation was com- 

 pleted, a layer of concrete composed of 5 parts of hydraulic lime, to 

 8 parts of sand, was spread over the bottom of the pit by means of a 

 trough of wood for the foundation stone to rest upon. After the stones 

 were laid, which was eftected by means of a heavy pair of shears, and 

 a "Lewis," the imoccupied space in the pit around the outside of the 

 stone bed, was filled with concrete and rubble stone, flush with the top 

 of the foundation stone. As it was only at, or near low water, that 

 this part of the work could be carried cju, that is to say ordinarily, 

 about three hours per day in good weather, considerable time was 

 necessarily consumed in getting in the foundation; from the day the 



> Vnrk atone or slate dowels and cr.imps are now g:uerally adopted in England ; tliej 

 aie far better and ch«ap«r.— Ed. C. E. & A. Journal. 



shears were erected, to the day the stone work was completed, was 

 just five weeks. 



Iron Work.— The figure of the beacon is that of a truncated pvra- 

 mid: it is formed of six wronght iron shafts, five of them 36 ft. 7 in. 

 in length, standing in the periphery of a circle of 16 ft. diameter, and 

 one 36 ft. long at the centre, the outer shafts incline towards the 

 middle in such proportion, as to fall at the top within the circumfer- 

 ence of a circle of 3ft. diameter; each of these shafts is composed of 

 two pieces of equal length, the diameter at the foot of the lower piece 

 is 5{in., and at the top 4in. ; the diameter of the upper piece is 4 in. 

 at the foot, and 3 in. at the top, they are united by a cast iron socket 

 of 3 ft. in length, 2i in. thick at the joint of the shafts, which is at the 

 middle of the socket, 2in. thick at the top and bottom, and lin. thick 

 elsewhere ; the top of the lower shaft is made concave, and the bottom 

 of the upper shaft convex, fitting one into the other. At the distance 

 of one foot from the joint of the shafts, a steel key, 2 in. deep by i of 

 an inch wide, passes through the socket and each shaft to secure them 

 together; the sockets inside, and 18in. of the ends of the shafts are 

 turned and accurately fitted to each other. At a distance of 2-Sft. 

 from the foot of the lower shafts, are four shoulders one foot long, and 

 projecting, at the lower extremity, one inch from the shaft to form 

 points of support for the same at the surface of the f.uiudatiou stone. 

 Above and below the joints of the shafts, and at distances of 9 ft. and 

 IS ft. respectively above the top of the stone, are two sets of braces 

 extending from the middle shaft to each outer shaft, and from one 

 outer shaft to another, making ten in each set; the braces are of 

 wrought iron 2iin. square, the extremities are seemed by Ijin. screw 

 bolts to cast iron collars, these collars are strengthened by two wrought 

 iron bands, and are firmly attached to the shafts by steel keys ; the space 

 between the collar and shaft, and between the keys is filled with zinc ; 

 the braces are secured to the collars in such a manner that they serve 

 for ties in case of anv unforseen strain acting from the interior of the 

 beacon, such as might possibly be occasioned by ice, or any other 

 floating body. 



The tops'of the shafts are provided with shoulders to support a cast 

 iron cap, composed of five arms, each 3ft. in length, and 4in. in width, 

 strengthened by a rib, or flanch, of 31 in. in depth ; the shafts pass 

 through this cap 18 in. from the centre of it, and are there keyed in 

 place; a wrought iron band 3 in. wide, and i in. thick, is shrunk upon the 

 extremity of these arms to add to its strength ; from the ends of the arms 

 of tlie cap, 3 ft. from the centre, braces of 2 in. round iron descend 4 i ft. 

 to the mainshafls,and are there secured by screw bolts passing through 

 their extremities, and through the shafts also. At this junction of the 

 braces with the shafts, a wrought iron band, similar to that which en- 

 circles the cast iron cap, is fitted and bolted at a distance of 4:Jft. ; 

 again below this second band is a third band similar to the two others, 

 and similarly secured bv screw bolts through the shafts; finally, there 

 are 10 panels or gratings, 4S ft. long, corresponding in shape arid di- 

 mension with the wrought iron bands between the shafts, and the 

 wrciUght iron bands; these gratings are made of boiler iron ^kths of an 

 inch thick, with eight horizontal and three vertical slats, or bars, 3in. 

 wide, riveted together; the horizontal slats are 3iu. apart, but at the 

 distance of 500 yards, the top of the beacon presents the appearance 

 of [\n opaque body Ojft. long by 6ft. wide at the top aud bottom, and 

 4J ft. wide midway of the same. . ■ -, r 



'The feet of the iron shafts penetrate the stone foundation 25 ft., and 

 are secured in their places by heavy iron wedges fitted to the unoc- 

 cupied spaces between the sides of the holes iu the stone and the 

 shalts; the holes being inclined, and the braces between theshalts 

 being immoveable. It is evident that the feet cannot be withdrawn 

 from their places without rupture. Now, the braces are of 24 in. 

 square iron, and the thickness of the stone outside of the hole is 2Jlt. 

 and this would seem to present sufficient strength to resist a shock 

 from any ordinary cause. , , , , ., 



In addition to the concrete around the outside of the stone, and the 

 cramps and dowels to secure the same together, there are five iron 

 tiesofU in. diameter, extending from a collar of two inch wrougiit 

 iron, which surrounds the middle shaft, to each of the outer shafts to 

 which they are firmly and securely attached by means of heavy iron 

 stirrups ; the ends of the ties are furnished with screws and nuts, and 

 by this means cm be kept in a constant state of tension. This arrange- 

 iiient was resorted to as an additional means of preventing any ten- 

 dency there might be in the outer foundation stones to separate them- 

 selves from the middle stone. 



The beacon, as finished, stands 34ft. above low water, and 3ft. 

 higher than the old beacon; the cage, or grating, is painted black, and 

 the shafts verniilivu red. 



The iron work was executed in Boston by Messrs. Cyrus Alger & 

 Co., under the immediate superintendence of Mr. Lester; the entire 

 weight is upwards of 19,000lb. The foundation was prepaicd, and 



