LIGHTHOUSE ESTABLISHMENT, THE UNITED STATES. 



441 



is lighted by five windows. Eight flights of 

 spiral stairways furnish access to the watch- 

 room, the first seven of which make half a 

 revolution of a spiral, but the eighth a whole 

 revolution. This arrangement does away with 

 the incumbrance of a central shaft to support 

 a winding stairway, and allows of a better 

 lighted interior and of more room. The struc- 

 ture is 150 feet high from base to focal plane, 

 and 165 feet above the level of the sea ; shows 

 a first-order light, and cost about $100,000. 

 The spiral stripes shown in the cut are added 

 to distinguish it, as a day-mark, from adjacent 

 sea-lights. 



Many brick lighthouses of this type have 

 been built, among which are those at Cape 

 Hatteras, Currituck Beach, and Body's Island, 

 North Carolina; Morris Island, South Caro- 

 lina; Sand Island, Alabama; Caps Foulweath- 

 er, Point Arena, and Pigeon Point, on the Paci- 

 fic coast. 



Minot's Ledge lighthouse was almost the 

 first, if not the first, important structure 

 erected by the Lighthouse Board. Accord- 

 ing to General Barnard, himself an engineer 

 of wide fame, " it ranks, by the engineering 

 difficulties surrounding its erection, and by the 

 skill and science shown in the details of its 

 construction, among the chief of the great sea- 

 rock lighthouses of the world." [For an ac- 

 count of its erection, see Appletons' "Cyclo- 

 paedia," article LIGHTHOUSE.] The board gave 

 to the plan and its execution its freshest and 

 best powers, and the combined energies of all 

 its members. A careful survey of the rock 

 was made by Major Ogden, of the Topographi- 

 cal Engineers, and then, after a full considera- 

 tion of all the difficulties by the full board, 

 the preparation of the plan was devolved on 

 the chairman of its committee on engineering, 

 General Totten, then Chief of the Engineers 

 of the army, who planned the masonry tower 

 for this difficult position, and so successfully 

 that, with the exception of the lower stones of 

 the foundation, which had to be studied out of 

 the rock itself, and some details of the con- 

 struction, the tower was built throughout by 

 B. S. Alexander, then Lieutenant of Engineers, 

 according to the plans of General Totten. The 

 brief memoir left by Colonel Alexander, the 

 only authentic record of the construction of 

 the tower, brief and modest as it is, shows 

 that the skill and ability of the builder equaled 

 that of the designer, and the great tower 

 stands as a monument to both and to the board 

 that availed itself of their powers. The last 

 stone was laid June 29, 1860, five years from 

 the commencement, and the cost, including the 

 keepers' houses on shore, was about $300,000. 



Spectacle Reef lighthouse, a similar structure, 

 stands on a limestone reef at the northern end 

 of Lake Huron, near the Straits of Mackinaw, 

 which join it to Lake Michigan. The nenrest 

 land is ten and one half miles distant, but it is 

 sixteen miles from Scammon's Harbor, where 

 the work for it was prepared. The waves have 



a fetch of one hundred and seventy miles to 

 the southeastward, but the ice-fields, which are 

 here moved by a current, and which are thou- 

 sands of acres in area, and are often two feet 

 thick, had to be specially provided against, as, 

 when moving in mass, they have a force which 

 is almost irresistible. But this is overcome by 

 interposing a structure against which the ice is 

 crushed, and then its motion is so impeded 

 that it grounds on the shoal, on which there is 

 but seven feet of water, and forms a barrier 

 against other ice-fields. The tower (see cut) 

 is in shape the frustum of a cone, thirty- 

 two feet in diameter at the base, and eigh- 

 teen feet at the spring of the cornice, eighty 

 feet above the base. The cornice is six and 

 the parapet seven feet high. The focal plane 

 is four feet three inches above the top of the 

 parapet. The entire height of the masonry 

 above the base is ninety-three feet, and of the 

 focal plane ninety-seven feet three inches ; the 

 base is eleven feet below, and the focal plane 

 eighty-six feet three inches above the water. 

 For the first thirty -four feet, the tower is solid ; 

 from thence it is hollow, and in it are five 

 rooms one above the other, each fourteen feet 

 in diameter, with different heights, from nine 

 feet two inches to seven feet eight inches. The 

 walls of the hollow portion are five feet six 

 inches at the bottom, and taper to eighteen 

 inches at the spring of the cornice. The in- 

 terior is lined with a four-inch brick wall, be- 

 tween which and the masonry is a two-inch 

 air space. 



The blocks of stone below the cornice are 

 all two feet thick ; those of the solid portion 

 of the tower were cut to form a lock on each 

 other in each course, and the courses are fast- 

 ened together with vvrought-iron bolts two and 

 a half inches thick and two feet long, while the 

 lower course is bolted to the foundation-rock 

 with bolts three feet long, which enter the bed- 

 rock twenty-one inches, the other courses re- 

 ceiving the bolts for nine inches. Each bolt is 

 wedged at both ends, and the bolt-holes, which 

 were made with the diamond drill after the 

 stones were in place, are plugged with pure 

 Portland cement which is now as hard as the 

 stone itself. Hence the tower is in effect a 

 monolith. The stones were cut, as were those 

 of Minot's Ledge, at the depot, and fitted, 

 course by course, on a platform of masonry, and 

 the work was so well done there that a course 

 could be, under favorable circumstances, set, 

 drilled, and bolted in three days. The main 

 difficulty, however, lay, as in Minot's Ledge 

 tower, in the preparation of the foundation. 

 This was overcome by a pier of protection in- 

 closing a coffer dam. The pier was a crib- 

 work of twelve-inch timbers built upon ways 

 at the depot, as a ship might have been, when it 

 was launched, and towedby a number of steam- 

 ers to the reef and grounded on its site. It was 

 of wood, ninety-two feet square and twenty- 

 four feet high, having an inside space forty- 

 eight feet square, and was divided into compart- 



