the periphery of a circle of from 25 to 30 feet diameter, and one in the middle as a centre shaft; the whole properly braced to each other with wrought iron braces of from 2 to 3 inches diameter, and so arranged and secured that each shall act as a tie as well as brace. The shafts to be in-clined inwards, at a rate of about two inches to each foot of rise, and to be secured at top by a casting of appropriate dimensions-say within the circumference of a circle of 14 feet diameter, leaving a distance of about 3 feet for a railed passage-way outside of the house part, at the extremity of each arm of the casting, making a surface of 20 feet diameter at the top of the shafts. On this cast iron platform the keeper's house is to be erected, 14 feet diameter in the clear, and upon the keeper's house the lantern and reflectors are placed. Below the keeper's house or room, and inside of the shafts, a species of cellar or store room, 7 feet deep, and of the same diameter as the house, can be advantageously added. It is an essential condition in such a structure that the bottom of the cellar or store-room should be above the reach of the sea or the action of a passing

wave.

"In the English light-houses of this description from 12 to 14 feet is allowed between the bottom of the cellar and high water. But as the light-houses in all the English cases are built upon banks or spits, where the wave rolls by without breaking, such a distance, adequate in such a locality, would not, it was feared, fulfil the requisite condition upon the Minot's rock. It was therefore considered necessary to give to the cast iron platform in this case an elevation of about 50 feet above the base of the shafts.

"The base of the shafts coincides nearly with the line of low water, and, as the tide ordinarily rises nearly ten feet, and during spring tides and gales from twelve to fourteen feet, it would leave a space of not less than twenty-nine feet between high water and the bottom of the cellar room-a space which was considered as making ample allowance for the break of the sea.

"The most difficult and dilatory part of the operation consists in drilling the shaft-holes in the rock. It can be done only when the sea is smooth and tide below half-ebb. Each hole has to be from twelve to fourteen inches in diameter, in order to receive the wedges required to adjust and secure the piles; and, as the shaft holes have to be from four and a half to five feet deep, it is evident, from the description which has been given of the Minot's rock, that the drilling of these shaft-holes must be unavoidably a tedious and dilatory process, and, in reference to which, elements of probable cost are too variable to be accurately anticipated. Our efforts have been to have these holes drilled by contract. Few are competent to such work, and fewer are willing to undertake it. It is now, however, under contract with Mr. Benjamin Pomeroy, a person who unites in himself the requisite practical knowledge, the unceasing vigilance, and the unyielding perseverance which the work requires. The season was much advanced when he undertook the work, but early in October he had succeeded in drilling the centre hole and in erecting the centre shaft, and has since been busily engaged upon other holes, but already this central shaft is a beacon, and has demonstrated, by saving two vessels from being wrecked, the great value of the locality for a lighthouse.

"It has been previously remarked that the variable character of the ele.

ments of that part of the estimate which involved the drilling of the holes renders it impossible to give a sound estimate of the probable cost of this part of the work. The experience of the last season, however, has furnished a safer guide in this respect than we have heretofore had, and it is upon the results of that experience that the estimate for the additional sum now required to complete this light-house has been made." And in the annual report of 1848 it is said:

"This has been a work of extreme difficulty and of no little danger, and the results are a singular exhibition of the triumphs of peseverance and mechanical ingenuity. The rock is exposed to the whole burst of the Atlantic wave. A small portion of it, involving a circular area rarely exceeding twenty-five feet in diameter, is bare at low water and during very calm weather; but no part of this area is more than three feet above extreme low water, and during the slighest winds the sea breaks over the whole with great violence. Upon this small and extremely-exposed position a footing had to be obtained, and holes had to be drilled in the rock, in which were to be inserted the iron piles to sustain the structure. This short description will sufficiently apprize all those who have any knowledge of a seashore of the serious and continued difficulty of working on such a place. It gives me great pleasure to add that no lives have yet been lost in the work, although there have been several accidents, and additional pleasure to say that all the piles to sustain the work have been established, as well as the skeleton iron frame of the top, intended to connect the piles and to sustain the keeper's house and lantern; all serious difficulties are, therefore, overcome.

"The work has been under the superintendence of Captain Swift, of the corps, and the resident agent and contractor, Mr. Benjamin Pomeroy, a person of the most extraordinary perseverance, inexhaustible ingenuity, and well acquainted with working in such positions. The report of Captain Swift is hereto added as an appendix. A small appropriation of $4,500 is now required to procure and complete the illuminating apparatus for this light-house, which I believe will be found to be one of the most useful on that coast.

"At the date of the last annual report (October 15, 1847) the condition of the work at the Minots was stated, and some of the difficulties which attended the operations of that season were specified. As the frame or main structure may now be considered completed, a brief description of the work, and some details connected with it during the progress of construction, may be regarded as not uninteresting. Minot's rock, or, as they are generally designated, the Minots,' lie off the southeastern chop of Bostou bay about seventeen miles from the city, and something less than eight miles from the Boston light.

"These rocks or ledges, with others in their immediate vicinity, are known as the Cohasset rocks,' and have been the terror of mariners for a long period of years; they have been, probably, the cause of a greater number of wrecks than any other reefs or ledges upon the coast, lying, as they do, at the very entrance to the second city of the United States in point of tonnage, and, consequently, where vessels are continually passing and repassing. The Minots are sunken, and bare only at one quarter flood, and the trend of the coast in that direction from Boston bay being southeasterly, vessels bound in with the wind heavy at northeast are liable, if they fall to leeward of Boston light, to be driven upon these rocks..

"As evidence of the great necessity of a light at these dangerous rocks, I have in my possession, from a reliable source, a statement of the number of vessels, with their names and tonnage, which have struck upon the Cohasset rocks within the last thirty years, but mostly, as my informant remarks, within the last fifteen years, to wit: ships 10, brigs 14, schooners 16, sloops 3-total 43. Of these, 27 were a total loss. From all this, it may be clearly inferred that it became necessary that these hidden dan gers should be pointed out to the seamen, and instead of the fatal breaker to give him the first warning of his approach to danger, that there should be a friendly beacon erected upon the rock to guide him in the storm, and enable him to avoid the horrors of shipwreck; and these, doubtless, were the considerations which led to the enactment of the law for building the light house in question.

"The rock selected for the site of the light house is called the 'Outer Minot,' and lies farther seaward than others in the group known as the Cohasset rocks. At extreme low water an area of about thirty feet in di ameter is exposed, and the highest point in the rock is about three and a half feet above the line of low water. It is very rare, however, that a surface greater than twenty-five feet in diameter is left bare by the sea. The rock is granite, with vertical seams of trap rising through it.

"From observations upon the tides, made at Boston light-house by the coast survey, from June 7 to October 27, 1847, the following results were obtained; and, by the kind permission of the superintendent, communicated to me, together with a tracing of the coast from Boston light to Seit uate light.

Rise of highest tide

Mean rise and fall of tides

Do
Do

spring tides
neap tides

Feet. Inches.

"The form of the light-house frame is an octagon, of 25 feet diameter at base. The structure is formed of eight heavy wrought iron piles or shafts, placed at equal distances from each other, with one also at the centre. These piles were forged in two pieces each, and are connected together by very stout cast iron or gun-metal sockets, the interior of which is bored, and the pile ends are turned and secured to the sockets by means of large steel keys passing through the piles and the sockets. Above and below the joints or sockets, and connecting the middle pile with each outer pile, there extends a series of wrought iron braces, and the outer shafts are connected together by similar braces extending from one to the other, and thus the whole structure is tied together. At each of the angular points in the octagon and at the centre, a hole of twelve inches in diameter and five feet in depth is drilled in the rock, the outer holes with the inclination or batter given to the outer piles, and the middle hole vertical.

"The surface of the rock being irregular in shape, and the holes in each case five feet deep, it is evident that the piles must be of unusual lengths: the least length in the lower series is thirty-five and a quarter feet, the greatest is thirty-eight and three-quarters feet, and the others are of various intermediate lengths. The piles in the upper series are of uniform length, viz: twenty-five feet each. The inclination or batter of the piles towards the centre is such as to bring the heads of the upper piles within the periphery of a circle of fourteen feet diameter; and there, at an ele

vation of sixty feet above the base of the middle pile, or fifty-five feet above the highest point of the rock, the pile heads are secured to a heavy casting or cap, to the arms of which they are securely keyed and bolted. The middle shaft is eight inches in diameter at foot and six inches at top; and the outer shafts are eight inches at foot and four and a half inches at top. All of these are forged ten inches in diameter, at the point where they leave the surface of the rock, and taper uniformly down to eight inches diameter in both directions, within a distance of five feet. The lower braces, placed nineteen feet above the rock, are three and a half inches in diameter; the second series, nineteen and a half feet above the first, or thirty-eight and a half feet above the rock, are three inches in diameter; and a third series, introduced eight and a quarter feet below the cast-iron cap, to form the support of the floor of the store-room, is made of two and a half inch square iron.

"The outer piles being inclined towards the centre, and the piles and the braces being inflexible, it is clear that, so long as the braces remain in place, the pile cannot be withdrawn from the hole, for the whole structure acts as an inmense 'lewis;' either the braces must be ruptured or the rock itself must yield, before a pile can be displaced.

"Upon the pile-heads are cast iron sockets, furnished with arms three feet in length, pointing outwards. These sockets are keyed to the head of the piles, and are bolted to the arms of the cap or spider, flush with its upper surface; thus giving a diameter at top of twenty feet from out to out. The object of the arms is to afford support for a foot-way or gallery outside of the keeper's house, which is placed immediately on the cap, and there secured by bolts and keys.

"The keeper's house is octagonal in shape, and fourteen feet in diameter; the uprights or stanchions are of cast iron, and rest upon the cap, immediately over the pier heads, where they are secured with bolts and keys. These uprights are cast with double flanches, between which two-inch plank, tongued and grooved, are to be fitted horizontally, and at right angles to these another series of plank is to be set on end vertically, and together these form the side or frame of the house; upon this frame the roof will be placed; and finally, upon this the lantern will be set up.

"The drilling of the holes in the rock for the light-house occupied the better part of two seasons. The erection of the iron structure in place, it may be conceived, was comparatively a work of much less difficulty, and, with favorable weather, an undertaking requiring not much time. That some of the difficulties may be known of working down nine holes of twelve inches diameter and five feet in depth, in a rock of granite traversed by veins of the most obstinate trap, in a situation exposed to the delays produced by every breeze which had east in it, I will enumerate briefly, from the journal of operations kept at the rock, some of the details for future reference.

"Early in April, 1847, I visited Mr. Benjamin Pomeroy, the contractor, who had, in 1843, erected for me the Black Rock be icon in Long Island sound, (a structure built upon the same principle that the Minot Rock light is built upon,) to accompany me to Cohassett, with the view of inducing him to undertake the drilling of the holes by contract, and also to take the piles, braces, and cap at Messrs. Alger & Co.'s, South Boston, where the work was to be executed, and to erect them in place at the Minot. After waiting eight days at Cohasset for a favorable opportunity

to examine the rock we effected a landing, and, with the advantages of a smooth sea and a very low tide, made sufficient measurements to deter mine the probable area of sound rock which might be relied upon for the base of the proposed light house.

"The proposition made by Mr. Pomeroy, to drill the holes in the rock for the reception of the piles for the light-house, I considered too high, and consequently I declined it, and sought elsewhere for a competent individual to undertake the work. After advertising in the newspapers, I received proposals from Mr. James Savage, and entered into an agreement with him to drill the holes, but after some weeks' delay Mr. Savage abandoned the contract. I then recommended, and was authorized to accept, the proposals of Mr. Pomeroy, and he undertook the work at once, but by the failure of the first contractor the greater part of the best portion of the season (1847) was lost, and it was not until July 22 that the new contractor, Mr. Pomeroy, actually commenced work upon the rock.

"The mode of working the holes down had for some time occupied the thoughts of the contractor, and he became satisfied that holes of the magnitude required in that exposed situation, where the sea was so continually breaking over the rock, could be drilled by machinery only, and that it would be necessary to have that machinery elevated beyond the ordinary reach of the sea.

"The drill used was of a peculiar form, with an edge in shape somewhat similar to the letter Z, made of the best cast steel, and fitted to an iron shaft some 30 feet in length, and weighing, with the drill attached, about 600 pounds.

"The machine for working the drill was a wheel and axle, furaished with tooth and pinion, and a crank or windlass at each end; this was placed on a frame of stout oak, and it required the power of four men to work it effectively. A cam and a fly-wheel were attached to the axle, and at every revolution the drill was raised about eight inches, and driven ordinarily at the rate of about fifty strokes per minute, the men being relieved every twenty minutes.

"To support this machine, it was necessary to erect upon the rock a triangle or shears of very heavy spars, secured at their feet by means of pir.tles, and chained down to lewis-bolts inserted in the rock; upon the triangle was placed a platform, and upon this the machine was worked, the drill being kept at the proper degree of inclination for the hole by means of guides, through which the shaft moved up and down. The whole arrangement answered the purpose admirably well, and the holes were cut as truly and as perfectly as an auger-hole could be cut in a piece of wood. "The triangle and drilling machine were swept from the rock twice by the sea during the first season's operations, and the men were frequently washed from the rock, but happily no lives have been lost. The work was suspended at the rock on the 25th October, 1847; and by reference to the journal of operations, noted carefully day by day, it will be seen how short a space of time can be reckoned upon for work in a situation so exposed.

"In the report of the contractor of the 8th November, 1847, accompanying the journal of operations for that season, is the following remark:

"It will be seen by my journal that, from the 22d July to the 25th October, I was able to land on the rock to do work only twenty-five days, viz: five days in July, thirteen in August, seven in September, and noue