68 ANNUAL OF SCIENTIFIC DISCOVERY. 



The following description of the plan of this light-house was given by 

 the engineer who constructed it Captain W. H. Swift. The rock 

 upon which the light stood is bare at low water only ; and the utmost 

 extent of surface exposed at the very lowest tide is an area of about 30 

 feet in diameter, but, in general, 25 feet is all that is uncovered ; and, 

 even of that extent, the sea must be very smooth and the wind off the 

 land. The nearest point to the shore is distant one and a quarter miles 

 only ; but, seaward, it is entirely open to the Atlantic, and. of course, 

 exposed to all its violence in an easterly gale. 



The structure was composed of nine piles or shafts, made of the 

 best description of wrought-iron, from 60 to 63 feet in length, each 

 pile inserted five feet deep in the solid part of the rock. All of them 

 were eight inches in diameter at the foot, ten inches in diameter at 

 a point five feet above the foot (at the surface of the rock) ; the 

 middle pile was six inches in diameter at top, and the outer piles four 

 and a half inches. These piles stood in the periphery of a circle of 

 25 feet, with one in the centre. They were united or connected 

 at five different points, to wit ; at the rock, where each pile was 

 secured in its place by means of iron wedges, and a cement of iron 

 filings. 2d. At a point 20 feet above the rock, by means of 16 

 wrought-iron horizontal braces, three and a half inches diameter, 

 radiating from the middle pile to each outer pile, and extending, 

 also, between each pair of outer piles. 3d. By a similar series of 

 braces, at a point 40 feet above the rock. 4th. By a like series, at a 

 point 47 feet above the rock, forming the support of the store-room, or 

 cellar. 5th. By means of a cast-iron cap, or spider frame, 14 feet in 

 diameter, and weighing five tons, to which were united and secured all 

 the pile-heads. This frame formed the base or support of the keeper's 

 house, eight feet high. Upon this was placed the lantern, of iron and 

 glass, six feet in height, thus making the entire elevation of the struc- 

 ture, above the rock, about 70 feet, standing upon a base of 25 feet. In 

 addition to the horizontal braces, a series of wrought-iron vertical tie- 

 rods, 32 in number, were introduced between the first and second series 

 of braces. The object of these ties was to stiffen the piles and prevent 

 vibration. 



From the preceding description it will be seen that there was a series 

 of braces, 40 feet above the rock. Upon these, the keeper had im- 

 properly built a sort of deck or platform, for the stowage of heavy arti- 

 cles. This deck, in addition to the weight placed upon it, was fastened 

 to the piles and braces, thus offering a large surface for the sea to strike 

 against. In addition to this, the keeper had attached a five and half 

 inch hawser to the lantern deck, 63 feet above the rock, and anchored 

 the other end to a granite block, some fifty fathoms from the base of 

 the light. The object of this was to provide means for running a box, 

 or landing-chair, up and down. It is clear that so much surface ex- 

 posed to the moving sea had the same effect upon the light-house, as 

 \voukl have been produced by a number of men pulling at a rope at- 

 tached to the highest part of the structure, with the design of pulling 

 it down. Since the destruction of the light, it has been ascertained 

 that the rock to which the hawser was attached, was washed in shore 

 400 or 500 feet. This r.i(.-k was estimated to weigh seven tons. 



