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no other case. A thorough trial and proof will be made of all others which this bureau has to construct, before they will be allowed to pass out ot our hands. Then, if injury should come to them from incompetent or negligent management, it will be known to whom it should be attributed. The last report in reference to the Minot's rock light is of as late date as the 21st October, 1850, from Captain W. H. Swift. I subjoin a copy of it: "In obedience to your instructions of the 2d instant, I have the honor to state that I have made the examination of the light house at Minot's rock, Cohasset, as directed.

"In Boston I called upon the collector of the port, Philip Greely, esq., and ascertained from him that the Treasury Department had instructed him to afford all necessary facilities for the examination, and for doing such work as might be found requisite at the light-house. The collector placed the cutter at my disposal, and offered whatever assistance I might need, but I preferred, as the more speedy method of making the examination, to go by land to Cohasset, and there taking a boat to the light; therefore did not avail myself of the collector's offer of the revenue cutter. "I was much gratified to find on my arrival at the light-house that all there appeared well, and, in the examination which I made while there, satisfied myself that the structure was really in as good condition as it was when delivered over to the Treasury Department in December, 1849. With the exception of the painting between the reach of the sea, worn off by the constant action of the breakers, all appears as it was left on the day it was turned over to the Treasury Department. Nothing what ever had started; every brace and every tie is in its place, and not the slightest indication of yielding at the foot of the piles where they are inserted in the rock; not even a crack in the cement or paint at the coup lings, nor at the collars where the braces are attached to the piles-these two last the places, of all others, at which the first evidence of weakness or working in the structure would show itself. In short, as the builder of the light-house, I was perfectly satisfied with its condition.

"All that the structure itself now needs is the lower tier of iron ties connecting the piles, at the points where they enter the rock, with the contiguous piles, at a point some twenty feet above and immediately below the first or lower series of horizontal braces, as explained in former reports. These iron ties, as the bureau knows, were procured and fitted, in part, last year, but as there were not sufficient funds to provide and place both the upper and lower series, the whole was not done. The first named only were placed. Congress, at the last day of its last session, having appropriated the means asked for in October, 1849, for the pur pose, the work can now be done, and I have made the necessary arrangements for having it done forth with.

"I have said that the first or upper series of ties were in place. This was done at the close of the season last year. The clasps or iron lubs to which the lower ties are to be attached are in place, in part, viz: all the upper clasps are attached in the lower series, and the lower clasp of the middle pile is also attached, but the others, eight in number, are not placed; they are in Cohasset and ready to be attached to the piles. These being fixed in their proper position, the ties themselves, of round iron one and a half inch in diameter, with screw ends and nuts for adjustment, are to be put in and set up with the proper degree of tension, and that operation will complete all that the structure itself will require-that is to

say, thirty-two ties in all. These are prepared in two pieces each, with the threads cut and the nuts provided. All that remains is to ascertain the exact length of the ties, and then to weld the two pieces together. It is evident that this cannot be done until the clasp is in the precise place it is to occupy; and, when fixed, the exact length of each tie will be known. The irregularity of the surface of the rock, of course, has required the piles, and consequently the ties to be of unequal lengths.

"I took Mr. Hosea B. Dennison with me when I visited the light-house. He was one employed in the building of it, and had the charge of fitting up the wood-work, under the direction of Mr. William Dennison, my assistant; and he also had the charge of the work of putting in the upper ties. Being thus conversant with the exact thing to be done, I have employed him to put in the lower series of ties, so that I hope to be able to report to the bureau the completion of the work within a month. The progress depends entirely upon the weather; but I hope, notwithstanding the late season of the year for such an operation, that we may have a suf ficient number of days suitable for this purpose within the time specified. "I must now beg to call your attention to a matter less agreeable in its character, but one which interests me both professionally and as the agent of the United States selected by the bureau to build the light-house. Various idle rumors and some ill-natured and vindictive reports have been circulated for some time, I find, in regard to the alleged insecurity of the Minot light. The effect of these stories, if not contradicted, may be injurious; and the bureau, by implication, may be censured for giving its sanction to a mode of construction declared unsafe by certain persons possessing neither the knowledge nor the capacity necessary to constitute them judges of the merits or demerits of the structure known as the 'screw or iron pile light'-a mode of construction hitherto new on this side of the Atlantic, but one which has been in successful use in very exposed situations in Great Britain and Ireland for a number of years.

"The screw-pile light, as it is called in England, possesses three very important advantages; and notwithstanding it may not be as unyielding as a column of granite, it may, for all the purposes for which a lighthouse is needed, be quite as useful. The Eddystone, the Bell Rock, and the Skerrigone light houses are all lasting monuments of the names and the skill of the several engineers who have built them; but in comparing these magnificent works with the simple and rapidly constructed screwpile light, we shall find, while the latter may cost from $30,000 to $60,000, that the stone columns enumerated have cost from $250,000 the least up to $500,000 the greatest; and we may add, the last built (the Skerrigone) in point of time, also, the comparison was equaily favor able to the screw-pile.

"In Great Britain all the screw-pile lights which have been erected are upon sand or other earth foundations, requiring the use of the screw at the end of the pile-the same being the case with that built under the direction of the bureau on the Brandywine shoal; but at the Minot, it was necessary to modify the construction, for the light has to be erected upon a sunken rock bare only at or near low-water, and not even then unless with a remarkably calm sea, as the fact stated in the report for the year 1848 will show-sixty hours only during the working season of that year (from July to October) being all the time that it was possible to work by hand-drills upon the rock itself. Instead of the screw at this locality, it

became necessary to bore holes in the rock of sufficient size to receive the ends or feet of the iron piles or posts for the support of the light and the dwelling of the keeper, together with storehouse for provisions, oil, fuel, water, &c. In this case the holes were made twelve inches in diameter, and five feet deep. Nine such were put down-one at the centre, and eight at the circumference of a circle of twenty-five feet diameter, the utmost space which was laid bare at the lowest tides. The posts or piles are of the best description of anchor iron, forged for the purpose by the South Boston Iron Company. At foot the lower posts were eight inches in diameter, and six inches at top. At the point where they come in contact with the surface of the rock, the size is increased to ten inches diameter, tapering in both directions for a distance in the pile of five feetthe object of thus strengthening them being to prevent the possibility of a fracture of the pile at the point, which may be considered the fulcrum of the lever the force of the sea against the pile and the force of the wind against the dwelling-house and lantern being exerted against the piles, and concentrated in some degree at the surface of the rock. The feet of the piles are secured in the holes in the rock by means of long iron wedges fitted to the spaces they were to occupy. The residue of this space was filled with iron filings, and by the action of the sea water converted into a very tenacious cement. Twenty feet above the rock the first tier of braces are inserted. These are composed of wrought iron, also round, and three and a half inches diameter, connecting all the piles with the central pile, and the outer piles one with another, and forming together an unbroken net-work. The middle pile is vertical; the outer piles batter 1 inch to the foot. It is clear, therefore, that the whole of the lower piles act like a 'lewis,' and unless the braces yi-ld, the piles break, or the rock itself disruptured, that the structure cannot be overturned.

"I am thus particular in repeating details which I have heretofore stated in former reports, because it has been asserted that the force of the sea, in striking the piles, will one day overturn the structure. That there will be a sensible vibration at the top of a pile or pole sixty feet long, no matter how well it may be braced and tied, and with its foot thoroughly secured in a hole five feet deep in solid rock, is not to be denied; still it is not to follow, that such vibration affects in any degree the safety of the structure, or its usefulness. The iron is an elastic material, and, like the spire of a church in a gale of wind, may have a palpable motion and be quite as safe, as experience shows every day, as if it were entirely rigid. Even in the massy column of the Bell Rock light, where the tower is forty-two feet at the base and one hundred feet in height, Mr. Stevenson, the engi neer and builder, states that the force exerted upon it by the sea, in a gale of wind, produced sensible motion at the lantern.

"The false and injurious statements to which I have referred, I do not deem it necessary or expedient here to repeat, or to exhibit the motives which I may suppose have actuated the writers and circulators of the reports in question. I trust that my statement in regard to the present condition of the light-house itself is a sufficient answer to the falsehoods which have, with some industry, been propagated.

"In my former reports upon this work, I stated the necessity of having a keeper at this exposed light accustomed to the sea and its dangers; one who would comprehend the difference between the condition consequent

upon living upon the top of nine iron poles stuck upon a sunken rock in the open ocean, and sixty feet above it, exposed to the fury of everlasting breakers, and that of a comfortable and quiet residence in some snug dwelling-house upon the shore. The bureau, I know, adopted this view, and communicated it to the proper department at the time, but in the appointment of a keeper no regard was paid to the suggestion, and one was appointed entirely unfit for the place an old man, as I understand, very well fitted for some shore light, but in all respects not suited to the Minot. The person referred to has lately been removed, and his successor appears in all respects to be the kind of man fit to be charged with the care of this important light. He is at home upon the sea, intelligent, energetic, and anxious, evidently, to make the light what it should be.

"I made a report in December last, and enclosed a statement from Mr. Dennison, of certain alterations made by the former keeper-all wrong as possible, the result of ignorance. These alterations have made it neces sary to have an additional provision made for ventilation of the lantern; for this, I have given the necessary directions to Mr. Dennison.

"The collector will do all in his power, I am satisfied, to have the light at the Minot well kept, and will cause the keeper to be provided with all that is necessary to enable him to discharge his duties efficiently.

"At my suggestion, Mr. Greely has directed a bell of suitable size, six hundred pounds, to be sent down to the light at once, to be used there in warning vessels off in times of fog and thick weather.

"In speaking of the screw-pile light in England, I have omitted to notice. the structure which was destroyed, in 1849, at Bishop's rock.

"In the newspaper account, it was stated that while this work was in progress, it was swept from the rock in a gale of wind, but by the same account it appears that one of the essential principles, peculiar to the screwpile light, had been disregarded in the construction; that is to say, instead of the common pile in the middle, usual in all the other structures, the en gineer had at Bishop's rock introduced a cast iron column in the middle, of three feet in diameter, to serve as a stairway. It is unnecessary to add that so large a surface exposed to the fury of the sea must have led to the destruction of the light-house, and it is very clear that such a departure from the usual mode of constructing the screw-pile light is sufficient to justify the supposition that the destruction was caused by the introduction of the column. And it may be added, also, that there is nothing in the account, as given in the newspaper, which should in any degree impair confidence in the stability of the screw pile light, when the structure is put up in the usual or proper manner.'

From the foregoing account of these several light houses, it will be seen that they constitute a selection of extremely difficult works-perhaps the most difficult works of that kind ever erected in our country. I know of none to compare with them; but of this I do not complain The bureau is ready and willing to put up a light-house anywhere; it only asks that its work will be judged of by the difficulues attending upon them, and it holds itself answerable always to show that its plans are judicious, and that the execution of them will exhibit practical skill and sound mechanical consideration and arrangements, and a rigid attention to economy of cost.

In addition to these important and critical works, there are two other light-houses, of which the erection is made by law a duty of this bureau:

one at or near the end of the north pier at Chicago, for which $15,000 was appropriated by the act of 3d March, 1849; and under the same act, at the mouth of Calumet (Calymick) river, a light-house is to be erected, for which four thousand dollars was appropriated.

The immediate superintendence of these works was committed to Lieutenant Webster, of the corps, then stationed at Chicago.

The Chicago light. In reference to this work he says, in a letter dated 7th July, 1849:

"I enclose herewith a plan and estimate for the foundation of the light-house at the end of the north pier. The whole subject of lighthouse construction was somewhat new to me; and, as I intimated in my letter of 23d ultimo, I have had some difficulty in deciding upon the best method of construction for the locality intimated in the law. I supposed it necessary also to keep within the limits of the appropriation for the object, if practicable. I should have felt more ready to offer a project less well digested, had I not foreseen that it would not be prac ticable to do more than put down the foundation this fall, as it will be necessary to observe the effects of the winter storms and currents upon it before proceeding with the superstructure.

"I began with the supposition that the method of commencing the foundation would be the sinking of a crib or cribs of suitable shape and dimensions, to be loaded with stone and further secured by piles, upon the general method heretofore pursued in the construction of the piers; and, considering the great expense as well as weight of a stone superstructure, I at once decided that the light-house should be of iron; and, as that would very probably be octagonal in its plan, I devised an octag onal frame-work for the foundation, and had nearly completed the plan of the whole structure in detail, when an apparent deficiency in strength of the frame struck me, and I substituted for it the plan now submitted. The breadth is forty-four feet. This I thought a good breadth of founda tion for an iron light house sixty-five (65) feet high, with a base of twenty-five (25) feet. I propose to fill this crib with stone, putting in at first so much as may be necessary to secure it for the time being-say thirty or forty cords. Upon this first or lower layer of heavy stone I propose throwing small stone, which, by the action of the water, will be well worked into the instertices of the larger stone. Then the same process is to be repeated, till sufficient stone has been put in to secure the crib against the worst storms of winter. The plan of crib appears to me to be as good a combination of timber as the dimensions of the ties procurable here will well admit. To make the crib larger, I should be obliged to make the long ties of built beams; and to make the foundation of several separate cribs, it seemed to me would endanger its stability in such deep water. The outer crib of the north pier is so much out of its perpendicular position as to be quite unsuitable to be included in the foundation for the light-house. In addition to the piles usually driven at the junction of the ties with the siding, you perceive I propose driving a good number in the interior. These I propose cutting off below lowwater mark to receive a grillage, to be itself imbedded in a body of concrete resting upon the broken stone beneath, to be put on after the stone in the interior shall have ceased to settle-the whole to form a bed for cut masonry of heavy stone, to be commenced two feet or eighteen inches.

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