II 
 
 27th Congress, Doc. No. 27. Ho. of Reps: 
 
 3d Session. Navy Dept, 
 
 FLOATING DOCK AT BROOKLYN. 
 
 LETTER 
 
 FKOX 
 
 THE SECRETARY OF TFIE NAVY, 
 
 BESPKCTI^G 
 
 The Floating Dock at Brooklyn. 
 December 22, 1842. 
 
 Referred to the Commiuce on Naval^Vffairs. 
 
 Navy Department, December 20, 1S42. 
 
 Sir : In compliance with the resoUition of the House of Representatives 
 of the 17th instant, I have the honor to report : 
 
 By the second proviso of the act making appropriations for the naval 
 service for the year one thousand eight hundred and forty-two," it is en- 
 acted '*'that the Secretary of the Navy may, in his discretion, apply the 
 sum of one hundred thousand dollars of the amount hereby appropriated, 
 and any balance of former appropriations for the construction of a dry 
 dock at Brooklyn, New York, to the construction of a floating dock at the 
 same place ; and if any part of this appropriation shall be expended upon 
 the construction of a floating dock, as hereby authorized, the construction 
 of the dry dock shall be suspended until the further order of Congress." 
 
 I have given to this law the following construction : As the dry dock is 
 already commenced in the navy yard at Brooklyn, upon land undoubtedly 
 belonging to the United States, the direction that no part of the appro- 
 priation shall be applied to that object, with certain exceptions, "until a 
 suitable place shall he selected in the harbor of New York, and the title 
 to the land obtained," &:c., is understood to mean that the Secretary of the 
 Navy shall select such suitable place, without reference to what has already 
 been done towards constructing that dock. If the intention had been to 
 limit the selection to the different positions in the yard itself, there would 
 have been no necessity for any provision for obtaining the title to the 
 land ; nor would so wide a range have been given as the harbor of 
 New York," which extends a great distance on two rivers. It is also 
 considered altogether improbable that Congress designed to separate the 
 dry dock from the navy yard ; and, consequently, it is to be inferred that 
 if a " suitable place" for the former should be selected out of the limits 
 of the present yard, the whole establishment would be moved to such new 
 
, 2 Doc. Xo. 27. 
 
 ^ locality. The duty, therefore, which the law devolved on me embraced^, 
 according to my understanding of it, the selection of a new site for the 
 navy yard, as well as of one for the dry dock, if it should appear advisable 
 
 C to do so. 
 
 Qualifications of a peculiar kind, and such as I certainly do not possess, 
 are necessary for the proper performance of this duty. It is impossible to 
 suppose that Congress designed to devolve so important a task on my un- 
 aided judgment. That task seemed to me to require the joint counsels of 
 the navy officer and the civil engineer, and to demand the higherst order of 
 qualifications in both of them. I accordingly appointed Captains William 
 
 B. Shubrick and D. Connor, of the navy, and Moncure Robinson, Esq., 
 (whose reputation as a civil engineer is well known to the country,) to 
 make the necessary examinations, and to report the result to me. The 
 points to which their attention was called will appear from my letter of 
 instructions to them, hereto annexed, (marked No. 1.) They have per- 
 formed the duty intrusted to them in a highly satisfactory manner, and I 
 now present their report, (marked No. 2.) 
 
 It is admitted, on all hands, that the present dimensions of the Brooklyn 
 navy yard are too narrow for such an establishment as ought to be made 
 in so important a port. It became necessary, therefore, to ascertain whether 
 or not the requisite additit>nal land could be obtained, and at what prices. 
 For this purpose I have been favored with the kind assistance of Henry 
 
 C. Murphy, Esq., of Brooklyn, who gives me assurance that there will be 
 little or no difficulty in obtain itig all the additional land which will be re- 
 quired. A copy of his letter (marked No. 3) is herewith presented. It 
 seemed to me that the ability or inability of the Goverrmient to enlarge 
 the present yard to the required size would form a controlling considera- 
 tion in the inquiry whether the yard should or should not be continued 
 where it is. It is gratifymg to perceive, both from the letter of Mr. Mur- 
 phy and the report of the commissioners, that there will probably be no 
 difficulty on that point. 
 
 This is not the first time that the policy of continuing the Brooklyn navy 
 yard at its present location has been brought in question before Congress, 
 in December, 1836, the Secretary of the Navy transmitted, in answer to 
 a resolution of the House of Representatives, a report from L. Baldwin, 
 on the comparative advantages of various positions in the neighborhood 
 of New York; and again, on the 29th of March, 1S3S, the Navy Com- 
 missioners made a very full report on the same subject. To these docu- 
 ments, now on the files of the Government, I respectfully refer. They 
 confirm the conclusion to which the commissioners appointed by mj^self 
 have come, and, it is presumed, render it no longer doubtful that ihe 
 Brooklyn navy yard ought not to be disturbed. 
 
 Tins fact being assumed, the propriety of constructing the dock, whether 
 Availed or floating, loithin the yard, or within its waters, is too manifest 
 to admit of doubt. I have therefore only to express my entire concurrence 
 in the views of the commissioners on this point. 
 
 In determining whether the appropriation to the dry dock ought or 
 ought not to be withheld from that use, and applied to the construction of 
 a tloytmg dock, I was conscious of a still stronger necessity for calling to 
 my aid the scientific and practical knowledge of others. Many consider- 
 ations of a purely technical character enter into that inquiry. The me- 
 chanical power necessary to be appUed \ the strength and durability of the 
 
Doc. No. 27 
 
 3 
 
 materials used ; the effect on the structure of the ship by the pressure 
 appUed to her ; the security of the ship while in dock — these, and other 
 topics of like kind involved in the general inquiry, demand a variety of 
 information, scientific and practical, which very few men possess. As it 
 seemed to me to be very important that the results obtained should be 
 satisfactory and conclusive, I determined to intrust the matter to a com- 
 mission, combining all the requisite qualifications for prosecuting a thorough 
 investigation, and forming a correct decision. With this view, Captain 
 B. Kennon, of the navy, Colonel Samuel Humphreys, chief naval con- 
 structor, attached to this Department, and Professor Walter R. Johnson, 
 of Philadelphia, were selected. It is believed that a more competent com- 
 mission, or one combining in higlier degree all the knowledge and practi 
 cal skill required for such a service, could not have been formed. 
 
 In order to invite public attention to the subject, and to afford an oppor- 
 tunity for the presentation of all the various plans of floating docks now 
 in use, an advertisement, of which I annex a copy, (No. 4.) was inserted in 
 the public newspapers. 
 
 My letter of instructions to the commissioners (No. 5) will show the 
 points to which their attention was directed. 
 
 They entered upon their duties at the appointed time, and the result of 
 their labors is now communicafed in a copy of their report, (No. 6.) 
 
 I can add nothing to the views presented in this report. The wide range 
 of inquiry which it emhraces, the scientific calculations and results which 
 it presents, the careful investigation which it displays, and the sound aud 
 satisfactory conclusions to which it conducts us, entitle it to great confi- 
 dence and respect. I am not in possession of any information which would 
 enable me to throw additional light upon the subject. 
 
 In applying the information thus obtained to the actual condition of the 
 navy, I do not feel that I should be justified in recommending the con- 
 struction of any floating dock whatever in the harbor of New York. There 
 is no emercjency which^emands it. The dry docks of Gosport and Charles- 
 tov/n afford all needful facilities in repairing our vessels of war in time of 
 peace, and would be sufficient, even in time of war, and for a much larger 
 navy than our own, if we could be sure of commanding them at all times. 
 It would not be safe, however, to rely on one or two places only, what- 
 ever conveniences and facilities they might afford, since an enemy, superior 
 to us at sea, might effectually exclude us from them. Besides, it is very 
 important that ships needing repairs should be able to obtain them with- 
 out delay, and without the risk of a voyage to a distant port. A coast so 
 extended as ours ought to present at least five stations, affording the ne- 
 cessary facilities for the speedy and complete repairing of our vessels of 
 "War. Of these, there siiould be one in the Gulf of Mexico, and one on 
 the coast of Georgia. The former will he necessary for the repairs of ves- 
 sels which it will be indispensable to keep constantly in the Gulf of Mex- 
 ico, and which could not be sent to any Atlantic -port for repairs without 
 great risk and loss of time ; the latter will be necessary for a similar rea- 
 son. No part of our coast is more dangerous than that between Savannah 
 and Norfolk, and none which would more expose vessel, in a crippled 
 state, to the danger of capture in time of war. Our cruisers to the South 
 would be able to reach, without difficulty, a port in Georgia, Avhen it would 
 be impossible to reach one in the Chesapeake bay, or further North. These 
 two establishments would be sufficient for the southern portion of our 
 
4 
 
 Doc. No. 'Z7. 
 
 country ; the middle and northern portion of it would be amply provided 
 for by the present dry docks at Charlestown and Gosport, and by a similar 
 dock at New York. The great importance and vahie of that port, both in 
 a commercial and in a naval point of view, entitles it to a dock of the best 
 kind for the building and repairing of vessels of war. Of the superiority 
 of the walled or dry dock over any and all forms of floating dock, I en- 
 tertain no d^ubt whatever. The reasoning of the commissioners upon 
 that point is, in my opinion, perfectly conclusive ; and, as I am also of 
 opinion that a better position for a dry dock cannot be found *• in the har- 
 bor of New York" than that which has already been selected, I shall, un- 
 less otherwise directed, proceed with the dry dock at Brooklyn as rapidly 
 as the means at my disposal will allow. I respectfully suggest, however, 
 that a more favorable opportunity than the present, of obtaining the re- 
 quisite land for enlarging the Brooklyn navy yard will, probably, not 
 soon occur. The importance, and indeed the absolute necessity, of this 
 enlargement no longer admits of doubt. 
 
 Although the excavated or walled dock is, in my opinion, the only one 
 on which we can safely refy as a permanent establishment, yet it cannot 
 be doubted that the floating dock may be very advantageously used as an 
 auxiliary. I cannot recommend it as a substitute at any place which ad- 
 mits of the construction of a walled dock at reasonable cost, and it is at 
 least doubtful whether it would answer for any vessel of a larger class 
 than a sloop of war. In consequence of the shallowness of the harbors 
 throughout the Gulf of Mexico, the vessels destined to cruise there and in 
 the Caribbean sea will necessarily be of small size and light draught. For tho 
 repairs of such vessels, a floating dock would afl'ord all needful facilities. 
 There is not, therefore, any necessity for the construction of a walled dock 
 on the Gulf of Mexico, nor will there be at any time during the continu- 
 ance of peace. If it should hereafter be deemed necessary to make pro- 
 vision for a diflerent state of things, the delay which the convenience of 
 the Treasury may require will occasion no inconvenience to the navy, if 
 a floating dock should be provided of sufficient power to take up a sloop 
 of war. The cost of such a dock would be very inconsiderable, and, if 
 properly constructed and properly taken care of, it would last twenty 
 years. Such a dock, built at Pensacola, would be of great value in the 
 arrangements of this Department. It is of great importance that our ves- 
 sels of war should be frequently seen in the ports of the Gulf of Mexico ; 
 and, to effect this, a certain portion of them should be kept at all times in 
 that Gulf. The necessity which they are now under of making a long, 
 tedious, and dangerous run to Norfolk or Boston, wlienever the most tri- 
 fling repairs to their bottoms are necessary, renders it almost impossible to 
 keep them in the Gulf of Mexico for any length of time. Hence the in- 
 terests of our commerce in that Gulf cannot receive from the navy the 
 attention which they require. A small appropriation would enable the 
 Department to provide, in the course of the ensuing summer, the necessary 
 means of repairing all vessels which it will be necessary to keep on that 
 station, and consequently to afford at ail times whatever protection or as- 
 sistance our commer||^may need from our naval power. 
 
 It is a task of some difficulty to decide between the several plans of 
 floating docks which have been presented. The commissioners give the 
 preference to that of Mr. Gilbert. In point of power and effectiveness, it 
 is not superior, and perhaps not equal, to the section dock offered by Mr. 
 
Moc. No 27 
 
 5 
 
 Dakin. Its great recommendations are its comparative cheapness, thesim- 
 plicity of its construction, and the comparatively small depth of water 
 which it requires. This last is a controlling consideration. There is rea- 
 son to fear that the section dock of Mr. Dakin, of sufficient size and power 
 to take up a sloop of war, could not perform its function in the harbor of 
 Pensacola. It has been suggested to me, however, that the floats of his 
 dock may be so constructed as to require a much less depth of water than 
 those which were exhibited to the commissioners ; and, if so, a very form- 
 idable objection toliis plan will be removed. I have no doubt that either 
 of these two docks would answer every purpose, and I have very little 
 preference for the one over the other. In addition to the testimonials 
 herewith submitted, there are many others, of a strong character, in favor 
 of both the plans now on the files of the Department. These will be fur- 
 nished, if it should he the pleasure of Congress to call for them. They are 
 not now sent, only because other and more pressing engagements now oc- 
 cupy the clerks of the Department, so that copies could not be conveniently 
 taken in time for this report. 
 
 The Pennsylvania, the largest ship in our navy, is three thousand two 
 hundred and forty-one tons. A dock, therefore, with a lifting power of 
 three thousand five hundred tons, would be sufficient for any purpose to 
 which it would ever be desirable to apply it. To take a ship of war into 
 a dock of any sort, with her armament on board, would be extremely haz- 
 ardous, and, it is presumed, would never be attempted. It is unnecessary, 
 therefore, to construct a dock with reference to such a purpose. 
 
 In conclusion, I respectfully recommend — 
 
 1. That an appropriation be made for the purchase of such lands as may 
 be necessary for the prof)er enlargement of the navy yard at Brooklyn. 
 
 2. That an appropriation be made for the construction of a floating dock 
 at Pensacola, of sufficient size and power to take up a sloop of war of the 
 first class. 
 
 Respectfully submitted. 
 
 A. P. UPSHUR 
 
 Hon. John White, 
 
 Speaker of the House of Representatives. 
 
 No. 1. 
 
 Navy Department, *-iugust 12, 1842. 
 
 Gentlemen : By the act of Congress making appropriations for the 
 naval service for the year 1S42, it is provided: "That no part of this or 
 any former appropriation to that object shall be applied to the construction 
 of a dry dock at Brooklyn, except in payment for materials previously 
 contracted for and yet to be delivered, until a suitable place shall be se- 
 lected in the harbor of New York, and the title to the land obtained, and 
 a plan and estimate of the cost made, under the direction of the Secretary 
 of the Navy, and approved by him and the Presider^gif' 
 
 This proviso seems to contemplate that no further proceedings shall be 
 had in the construction of the dry dock at Brooklyn, until Congress shall 
 have the means of determining whether or not a more suitable place can 
 be obtained within the harbor of New York. It may also involve the 
 
6 Doc. No. 27. 
 
 removal of the navy yard. It is necessary, therefore, that the Department 
 should be informed iully on every point connecied with both these views 
 of the subject. You are hereby appointed commissioners to obtain this 
 information, and, in the discharge of that duty, you will please embrace 
 the following objects : 
 
 1st. Yon will ascertain and report whether there is or is not, within the 
 harbor of New York, a position more favorable for a navy yard than that 
 at Brooklyn, designating the place, with a full detail of all the reasons 
 which induce you to prefer it. You will also ascertain whether or not the 
 land can be obtained, and at what price ; and, if it can be obtained, you 
 will also present a plan of the yard, and an estimate of the cost. Should 
 such selection be made, you will also present, ia connexion therewith, an 
 estimate of the value of the lands now occupied as a navy yard at Brook- 
 lyn, should the same be put to sale, and of such other property therein as 
 could not he advantageously removed to another position. 
 
 2d. If you should be of opinion that there is not, within the harbor of 
 New York, a more suitable place for a navy yard than the present one, 
 you will then ascertain whether or not there is a more suitable place 
 therein for a dry dock ; and, if you determine that there is, you will in like 
 manner ascertain whether or not the land can be obtained, and at what 
 price ; and you will present also a,n estimate of the cost of a dry dock at 
 such place. You will, in this case also, state at large the reasons which 
 govern your decision. 
 
 In calhng your attention specifically to the above objects, it is not my 
 intention to limit the range of your inquiries, nor to prescribe the topics to 
 which your report shall be confined. You will perceive that the object is 
 to obtain full information on every point necessary to decide the judgment 
 of Congress on the question whether the navy yard or the dry dock ought 
 or ought not to be removed from its present position to any other position 
 within the harbor of New York. The means of obtaining this informa- 
 tion are left to yourselves. You will consider as " within the harbor of 
 New York" every place within the State of New York sufficiently near 
 to the city to afford all the conveniences and faciUties which such an es- 
 tablishment can be supposed to derive from the neighborhood of a large 
 town. * 
 
 In the comparison which it will be necessary to institute between Brook- 
 lyn and other places, you will have reference to the present size of the 
 navy yard, and to the necessity which may exist of enlarging its limits. 
 You will of course ascertain whether or not such enlargement is practica- 
 ble, and what will be the cost of the ground required to be purchased. 
 
 I am, respectfully, &c. 
 
 A. P. UPSHUR. 
 
 Captain D. Connor, 
 Captain W. B. Shubrick, 
 MoNcuRE Robinson, Esq. 
 
 ^ No. 2. 
 
 Washington, October 27, 1842. 
 
 Sir : The undersigned, commissioners appointed by you, under your 
 communication of the 12th of August, <^ to ascertain and report whether 
 
Doc. No. 27. 
 
 7 
 
 there is or is not, within the harbor of New York, a position more favora- 
 ble for a navy yard than that at Brooklyn : and in case they shonld be of 
 opinion that there is not within the harbor of New York a more suitable 
 place for a navy yard than the present one, then to ascertain whether 
 there is a more suitable place for a dry dock," have the honor to report: 
 
 That, in their investigations on this subject, they have, agreeably to your 
 instructions, considered ''as within the harbor of New York every place 
 within the State of New York sufficiently near to the city to afford all the 
 conveniences and faciUties which such an establishment can be supposed 
 to derive from the neighborhood of a large towM and Iiave also, with a 
 view of fulfilhng as fully as practicable the objects of their appointment, 
 embraced in their investigations some other points which, though 720/ in 
 the State of New York, were on waters adjacent to the city, and which, 
 therefore, they supposed you would wish considered, with a view to the 
 determination of the question, whether the navy yard or the dry dock 
 ought or ought not to be removed." 
 
 The result of this extended examination has been a conviction in the 
 minds of each of the undersigned that no spot which could be obtained by 
 the Government, on any of the waters adjacent to the city of New York, 
 combines, in an equal degree, advantages for a naval establishment, with, 
 the present na,vy yard. 
 
 The commissioners have been brought to this conclusion by the follow- 
 ing considerations : 
 
 The points of most essential importance in the selection of a site for a 
 navy yard appear to them to be the following : 
 
 1. An adequate depth of water at the wharves for vessels of war of the 
 largest class. 
 
 2. Facility of ingress and egress. 
 
 3. Safety. 
 
 4. Adequate space for all necessary constructions. 
 
 5. Convenience in obtaining workmen, seamen, materials, and supplies. 
 It appeared, on an examination of the bay of New York, that its shores, 
 
 with the exception of about two miles, immediately above the fortifica- 
 tions at the Narrows, were precluded from considerations by their shoal- 
 ness. Witliin this distance of the Narrows there is good water on both 
 the Long Island and Staten Island shores ; but the exposure to floating ice 
 and winds, and to attack from an enemy which might effect a landing on 
 •either shore, below the fortifications at the Narrows, and, by a sudden in- 
 cursion, destroy the building and shipping at the yard, unless a separate 
 force was kept for its defence, unavailable for that of the city, or even of 
 the fortifications, seem to be insuperable objections to a site on this portion 
 of the bay. 
 
 Similar objections would apply to a site on the East river, whether on 
 the main land or on Long Island, between the fortifications at Throg^s 
 point and Hellgate. The coves and inlets in this distance are very shoal, 
 and it is not believed that a spot could be found preseniing very decided 
 advantages for a navy yard. But a serious obstacle to any site in this 
 distance, could one be procured, would be the necessity of providing for 
 its defence by a separate force from that which might be organized for 
 the defence of the city of New York and the towns of Brooklyn and 
 Williamsburg. Added to this objection would be the want of the facili- 
 ties and conveniences for building and equipment which a site nearer to 
 
€ Doc. 27. 
 
 New York would yjresent, and the consideration that the naval force whicli 
 might happen to be at a navy yard so located, which might be blockaded 
 by an enemy's fleet in the sound, could not be made use of, without en- 
 countering the pass at Hellgate, for the defence of the city and shippingp. 
 in the event of a threatened attack. These considerations made it, in the 
 opinion of the imdersigned, unnecessary to make the same minute examina- 
 tions of every portion of the shore in this distance which was made by 
 them at other points. 
 
 site on the Hudson, above Iloboken point, seemed to them out of 
 the question, in consequence of the difficulties and dangers to which ships 
 might be subjected, in approaching or leaving it, from floating ice in the 
 winter or spring. Above that point the ice, which below it is, on its 
 breaking up, usually accunudated on the east shore of the Hudson, leav- 
 ing the west comparatively free, is carried successively by the tides and 
 currents from the one to the other sliore, often in large masses, and making- 
 a passage up or down the river for any vessel, not sheathed with iron and 
 driven by steam, extremely dangerous, if not impracticable. 
 
 There appeared, then, to be controlling obstacles in the way of the adop- 
 tion of any site on either shore of the bay of New York — of the East 
 liver beyond Hellgate, and the Hudson above Hoboken — and that any el- 
 igible site for a navy yard, in waters adjacent to New York, must be found 
 either on the shores of the East river, between Governor's island and Hell- 
 gate ; on the western shore of the Hudson, below Hoboken point ; at one 
 of the islands in the bay; or in the Kills, separating Staten island from the 
 Jersey shore. 
 
 The commissioners have made an examination of every available point 
 Avithin this more limited range, but deem it unnecessary to lengthen this 
 report by enumerating objections to sites found on such examination to 
 present no circumstance in their favor, and will therefore confine them- 
 selves tg the consideration of those which seemed in one or more respects 
 worthy of comparison with the present navy yard. But three sites with- 
 in this range of examination seemed to them entided to such comparison. 
 These were the northwestern shore of Great Barn island. Governor's 
 island, and the western shore of the Hudson, immediately below Hoboken 
 point. 
 
 Comparing the first of the above-named sites with the Brooklyn navy- 
 yard, there seems to be in its favor the facility of obtaining, probably at a 
 iair rate, whatever ground might be required for the purposes of a navy 
 yard, and a sufficient depth of water. But all the other points, above enu- 
 merated as of essential importance in the selection of a site, would be in- 
 favor of the present yard. 
 
 In facility of ingress and egress, it would not compare with the Brook- 
 lyn navy yard, both because it is more remote from the sea by way of 
 Sandy Hook, and because it would not answer to approach or leave it 
 with light and variable winds, which might fail or change — in which case 
 there would be danger of a vessel being drawn into the currents setting- 
 through Hellgate, and thrown upon some of the rocks or reefs so designated. 
 
 In safety, the advantages would also preponderate in favor of Brook- 
 lyn, both as regards natural causes and an enemy. 'I'he anchorage is 
 bad, both in approaohing and on much of the bottom near Great Barn 
 island ; and there would be danger of vessels, unless well up in the chan- 
 nel between the island and the main land, being drawn from their moor-^ 
 
Doc. Ifo. 27. 
 
 9 
 
 iiigs by the strong currents which ofte*n set from the shores of the island 
 upon Hi'Ugate. The breaking of a cable, in such a situation, would be- 
 attended with great hazard. As regards atuick from an enemy, whilst the 
 risk would not be serious, a navy yard at Great Barn island labors under 
 this disadvantage, in comparison with one at Brooklyn: that the latter is 
 necessarily protected by the troops and defences which would he provided 
 for the defence of New York, whilst it would be necessary to modify these 
 with reference to the protection of the navy yard, were one established at 
 Great Barn island. 
 
 The navy yard at Brooklyn would also be obvioitlly much more con- 
 veniently situated for obtaining workmen, seamen, materials, and suppUes- 
 of every description ; and would possess the further advantage over a yard 
 at Great Barn island, that, if it were deemed advisable to employ the na- 
 val force at the station in combination with the other defences of the har- 
 bor, there would be a better guaranty of its being at every moment in the 
 most effective position, from the greater contiguity of the yard. 
 
 In a comparison of Governor's island with the present navy yard at 
 Brooklyn, there seems to be a near approach to equality of advantages, as 
 regards depth of water, convenience of access, space for necessary con- 
 struction, and supplies of all kinds ; though in one respect the present navy 
 yard has an important advantage over a navy yard at Governor's island — - 
 that of being situated in a cove, where men of war, lying at anchor or 
 moored, would be out of the way of vessels passing in and out of the har- 
 bor of New York, or to and from the sound. 
 
 In safety, Governor's island would in one aspect have an advantage in 
 its insular position, which would exampt it more completely than the yard 
 at Brooklyn could be from the attempts of incendiaries ; but, on the other 
 hand, the appropriation of Governor's island to the purposes of a navy 
 yard, instead of a fortification, (if, indeed, such an approi)riation is author- 
 ized by the terms of its grant to the Government.) would, in the opinion 
 of the commissioners, subject not only the yard itself, but the city and 
 shipping of New York, to greatly increased danger. They express their 
 opinion with some diffidence, because they are aware that it has been 
 thought by able engineers that the works executed and proposed by the- 
 Government, at the Narrows, would guaranty the harbor of New York 
 from attempts by a hostile naval force, however powerful. It seems to 
 them, however, that a bold commander might well, without incurring the 
 reproach of rashness, make the attempt to pass the works at the Narrows^ 
 even though much stronger than they are, with the knowledge that when 
 passed there was no obstacle in the way of his reaching New York and 
 destroying the public and private shipping, and putting the city under con- 
 tribution, when he would long hesitate if he had afterwards to expose 
 himself to the cross-fires of Governor's and Bedloe's islands ; and that, at 
 all events, the great interests concentrated at New York ought not to be 
 exposed to the contingency of the works at the Narrows being silenced., 
 or surrendered by force or through treachery, slight as such hazard might 
 be. If these views be correct, and an inner line of defence be advisable^ 
 the position of Governor's island is invaluable for this purpose ; and, wai- 
 ving other considerations, the extent of the island, (about .SS acres only,) 
 being not more than adequate to an extensive navy yard, would be insuf- 
 ficient for this purpose and a strong fortification. 
 
 To make use of the western shore of the Hudson, immediately below 
 
10 
 
 Doc. Xo. 27. 
 
 Hoboken point, it would be necesscfry, in order to break the force of the 
 current, to throw a jettee down stream from this point, at an angle of about 
 30 degrees with the shore. Such a jettee would probably be objected to, 
 on account of its tendency to throw the current more towards the eastern 
 shore than at present, and to increase the accumulation of ice, during win- 
 ter, against the wharves on the New York side of the river; but, by means 
 of it, men of war might, at most periods of the year, and except under par- 
 ticular circumstances, have safe access to a navy yard placed on the west- 
 ern shore of the Hudson, between Hoboken point and a village of that 
 name. With such •jettee, the following comparison would hold between 
 a navy yard at this site and the present navy yard at Brooklyn: 
 
 1. As to depth of water, each site would present nearly equal advan- 
 tages ; the site at Hoboken requiring only moderate wharves to obtain any 
 requisite depth, whilst at the Brooklyn navy yard the depth of water is al- 
 ready ample, though some expenditure in walling and dredging will be 
 requisite, to attain a sufficient width of adequate depth. 
 
 2. As to facility of ingress and egress, the case is also nearly a bal- 
 anced one, but is probably somewhat in favor of the present navy yard, 
 as, when the Hudson is very full of floating ice, with easterly or north- 
 easterly winds, vessels would be unable with entire safety to enter or leave 
 a navy yard at Hoboken. 
 
 3. As to safety, a navy yard at Hoboken would be more out of the way 
 of attack and in no danger of surprise by an enemy, which might land 
 unexpectedly, merely with a view to the destruction of the yard, looking 
 to an immediate retreat to its ships. But, in this respect, the danger to 
 the navy yard at Brooklyn, with the large population of Brooklyn and 
 Williamsburg, and its contiguity to New York, seems to be but slight: and, 
 as before observed, the circumstance that the necessary defences of New 
 York against a regular attack equally defend Brooklyn and the navy yard 
 seems to place the present site on as advantageous ground, or nearly so, in 
 regard to safety, as any other. 
 
 4. As to space for necessary construction, ground suitable to this purpose 
 at Hol)oken would be of limited extent-, and in this respect the present lo- 
 cation of the yard, even without any further extension of it, would be most 
 advantageous. 
 
 5. As to convenience in obtaining workmen, seamen, materials, and sup- 
 plies. In this respect, Hoboken would b3 favorably situated, but not as 
 much so as the present yard, which, being on the East river, the centre of 
 the trade of New York and Brooklyn, on which most of the private ship 
 yards are situated, and having all the facilities afforded by both towns, 
 would be more favorably situated than any other point. 
 
 It will appear, from the above comparison of sites, that if the question 
 was an original one, the balance of advantage would be in favor of the 
 present navy yard at Brooklyn. The large expenditures which have been 
 incurred by the Government at this place furnish, of course, under exist- 
 ing circumstances, a strong additional consideration in its behalf, which, 
 with those above presented, seems to the commissioners conclusive in favor 
 of the present site. 
 
 In making the above comparisons, the undersigned have not been un- 
 mindful of your instructions to have reference to the present size of the 
 navy yard, and to the necessity which may hereafter exist of increasing 
 its limits. There can be Uttle doubt that such necessity will exist at a 
 
Doc. JSTo. 27. 
 
 11 
 
 point which will probably always prove the most advantageous for the 
 rapid constrnction, repairs, and equipment of our ships of war. 
 
 The commissioners are informed that there will be no difficulty in the 
 Department's procuring, at fair rates, such additional property as it may 
 deem advisable to purchase adjacent to the present navy yard, whether 
 with a view to its future extension, or to its belter protection against tire. 
 With reference to the last-named object, it would probably be expedient 
 to purchase, if to be had at fair rates, the lots adjoining the northwestern 
 boundary of the yard as far as Little street, and, with a view to the future 
 extension of the yard, if to be had on similar terms, it would be desirable 
 to procure the margin of Wallabout bay, between the southern angle of 
 the yard and the hospital grounds. Should the Government be unable to 
 obtain this increase of s}>ace at fair prices, it will be attended with no very 
 serious expense to provide, within the present limits of the yard, the in- 
 creased accommodation which may be required. 
 
 The commissioners would advise, even without reference to such exten- 
 sion of the yard, the construction of a quay wall parallel, or nearly so, 
 to the present wharves of the yard, and about three hundred feet from 
 them, with a view to an increased water way of adequate depth. Such a 
 work seems to them an indispensable preliminary to the attainment of the 
 object, as, without it, a passage for ships to lie in, of greater width than, 
 that hitherto kept open by the tide, could not be maintained, without great 
 and constant expense in dredging, resulting, from the wash at each ebb 
 and flow of the tide, from the mud flats in the centre of the Wallabout. 
 Should such a quay w.-ill be constructed, the flats beyond it would rapidly 
 fill up in the more perfect eddy which would thereby be created, and the 
 operation might be hastened, by depositing in l.he flats beyond the wall all 
 future excavations from the yard. The necessary space, tor the future 
 wants of the Government, would probably be obtained in this way as early 
 as it might be wanted, should it not be found practicable, at a moderate 
 cost, to make the extensions of the yard which have been suggested. 
 
 The undersigned have now the honor to respond to that part of their 
 <:ommission by which they are required, in case they " should be of the 
 opinion that there is not within the harbor of New York a more suitable 
 place for a navy yard than the present one/^ then " to ascertain whether 
 there is a more suitable place for a dry dock.'' 
 
 The case is undoubtedly not a very favorable one for founding a dry 
 dock at the present navy yard, and probably there are many other posi- 
 tions in the harbor where such a work might be constructed at less ex- 
 pense. But the difficulties to be encountered are not greater than have 
 often been overcome in founding other works requiring similar precau- 
 tions ; and it appears to the undersigned that there is nothing in them to 
 justify placing elsewhere a structure so essential to the completeness of the 
 yard, and the use of which, at even a short distance from it, would be at- 
 tended with so much inconvenience. They concur, in this respect, entire- 
 iy in opinion with a distinguished engineer, (the late Colonel Baldwin,) for 
 some time in the service of the department, who, in a report dated July 11, 
 1835, on the subject of constructing a dry dock at the Brooklyn, navy yard, 
 or at Governor's island, observes : " The construction of a dock only at the 
 island seems so objectionable, and the objections are so strong against its 
 being placed any where, in separate ground, without the enclosure, that a 
 moment's reflection upon the inconvenience, increased expense, and de- 
 lays attending its use, will dissipate all thoughts of such an arrangement. 
 
12 
 
 Doc. No. 27. 
 
 " The dry dock is, in fact, a necessary workshop, where the whole ship 
 is taken in at once, and where every kind of workmanship, and all branches 
 of mechanic labor incident to the repairs, refitting, or rigging a vessel from 
 the keel to the main trnck, may be carried on at the same moment, and 
 even the armament, watering, and provisioning, be going on in the mean 
 time. 
 
 "A dry dock is therefore a necessary appendage to the yard ; it should 
 be near to and easily accessible from every workship, office, store, and 
 warehouse of the establishment. In this view, we consider a separation of 
 a dry dock from the other parts of a complete and well-ordered dock yard 
 as inadmissible." 
 
 For the elucidation of this report, the undersigned beg leave to refer to* 
 the published "maps of the harbor of New York, and to the maps, in the 
 department, of Great Barn island and the adjaceht waters, and of the pres- 
 ent navy yard at Brooklyn. 
 
 All of which is respectfully submitted. 
 
 W. BRANFORD SHUBRICK. 
 D. CONNOR. 
 MONCURE ROBINSON. 
 
 To the Secretary of the Navy. 
 
 No. 3. 
 
 Brooklyn, October 15, 1842. 
 
 Sir : Enclosed you will find the agreement in relation to the land be - 
 tween the navy yard and the hospital grounds at this city. It is signed • 
 by all the parties owning land there who are adults. In relation to the- 
 infants, the letter- of Judge Morse, their legal adviser, which is also en- 
 closed, will show the position in which they stand. They have deemed it 
 unnecessary to make application to the chancellor until the propositioa 
 shall be accepted, as it would be attended with expense. 
 
 It was intended to have the agreement re-engrossed and re-signed, but,, 
 as it would be attended with some delay to see all the parties again, it is 
 forwarded to you as it is. 
 
 Hoping that such speedy course will be pursued and measures taken as 
 will secure the object which I have in view for the city of Brooklyn, 
 
 1 remain yours, truly, 
 
 HEN. C. MURPHY. 
 
 Hon. A. P. Upshur, 
 
 Secretary of the Navy. 
 
 Brooklyn, October 3, 1S42. 
 
 Dear Sir : I have seen Mrs. Margaret Ryerson on the subject of the- 
 proposed offer of ground below Flushing avenue, in the Wallabout, to 
 the United States. She is prepared to make an application to the chan- 
 cellor for l^ave to join in such sale in behalf of her children, (they being 
 vuider age,) if the Government receive the proposition favorably. You 
 may confidently rely upon Mrs. Ryerson and her children joining you in 
 the proposed sale, if the same shall take place. I saw General Johnson 
 and Alderman Johnson, his son, who are the advisers of Mrs. Spader, and 
 
Doc. No. 27. 
 
 13 
 
 they informed me she would make the requisite application to chancery 
 in behalf of her children, and cordially join in the sale, if one should be 
 effected. 
 
 In haste, yours, truly, 
 
 N. B. MORSE. 
 
 William P. Wells, Esq. 
 
 Know all men by these presents, that we, the undersigned, owners of 
 land fronting on the Wallabout bay, between the United States navy yard 
 and the naval hospital ground, and lying north of Fhishing avenue, in the 
 seventh ward of the city of Brooklyn, in the county of Kings, and State of 
 New York, for and in consideration of the sum of one dollar, to each of us 
 in hand paid, the receipt whereof is hereby acknowledged, do hereby — each 
 for himself, his heirs, executors, and administrators — covenant, promise, 
 and agree, to and with Hon. A. P. Upshur, Secretary of the Navy of the 
 United States, and his successors in otfice, to convey to the United States 
 •of America, or their authorized agent, by a good and sufficient conversance 
 in the law, free and clear from all incumbrances whatsoever, all our and 
 each of our lots, pieces, or parcels of land, lying north of Flushing avenue, 
 in said city, and fronting on the Wallabout bay, between the United States 
 navy yard and the naval hospital grounds, as aforesaid, together with all 
 and singular our and each of our respective right, title, and interest, of, 
 in, and to the said lots, pieces, or parcels of land, and the land covered by 
 water, in front thereof, ni the Wallabout bay aforesaid, and our and each 
 of our respective rights, privileges, and easements, benefits and advantages, 
 which belong or in anywise appertain to the said premises, and to the 
 said Wallabout bay, or the waters thereof', or to us respectively, as the 
 owners thereof, upon the receipt of such sum and sums of money by us, 
 respectively, as may be fixed, determined, and agreed upon by three im- 
 partial and discreet persons, to be chosen, two of them, one each by the parties 
 interested, the third, by the two thus chosen for that purpose, from the in- 
 habitants of the city of lirooklyn, v/ithin six months from and after the date 
 of these presents, and to be sworn well an<l truly, and impartially to 
 appraise the just value of said lands and premises belonging to each of us, 
 respectively, (a proper sewer or sewers for tlie waters south of Flushing 
 avenue being reserved over said lands.) 
 
 In witness whereof, we have hereunto set our hands and seals, this twelfth 
 day of October, one thousand eight hundred and forty-two. 
 
 Sealed and delivered in the presence of 
 
 WILLIAM P.WELLS, 
 ROBERT S. MANLIE, 
 
 PETER Mccarty, 
 
 WM. H. GARY, 
 JOHN H. BAKER, 
 SAMUEL BOUTON, 
 WM. HUNTER, Jr., 
 H. L. CLARKE, 
 L. V. NOSTRAND, 
 J. S. MACK AY, 
 THOS. S. McCARTY, 
 • THE HEIRS OF COM. CHAUNCEY, 
 
14 
 
 Doc. No. 27. 
 
 In explanation of the above, "heirs of Com. Chaiincey," being written,' 
 in the iuforiual manner that it is, I wonld state that the Rev. Mr. Chaun- 
 cey, the Commodore's son, met me at the steamboat landing, this morning, 
 at Port Chester, and, imderstahding that a copy of tliis paper, with seals 
 attached, was to be submitted to the Government, he made the entry to 
 signify his approbation of the measure. 
 
 J. S. MACK AY. 
 
 Brooklyn, October 10, 1S42. 
 
 No. 4. 
 
 FLOATING DOCKS. 
 
 Navy Department, August 9, 1842. 
 
 By the act of Congress making appropriations for the naval service for 
 the year 1842, it is provided "that the Secretary of the Navy may, in 
 his discretion, apply the sum of one hundred thousand dollars of the 
 amount herehy appropriated, and any balance of former appropriations for 
 the construction of a dry doik at Brooklyn, New York, to the construction 
 of a floating dock at the same place ; and if any part of this appropriation 
 shall be expended upon the construction of a floating dock, as hereby au- 
 thorized, the construction of the dry dock shall be suspended until the 
 further order of Congress.'' 
 
 In order to carry out this purpose, I invite proposals for the construction 
 of a floating dock at New York. The proposals must be accompanied by — 
 
 1st. An exact description of the dock, with all its machinery, and also a 
 working model thereof. 
 
 2d. A specification of the kind of timber out of which its several parts 
 shall be built. 
 
 3d. The prices of docks of three diff'erent sizes — the first for ships of the 
 line, the second for frigates of the first class, and the third for sloops of war 
 and smaller vessels. 
 
 4th. The draught of water, when light, ®f a dock of each of the above- 
 mentioned sizes. 
 
 5th. The length of time and number of hands required to take up a ves- 
 sel, and to prepare her for receiving repairs. 
 
 Every part of the dock exposed to the action of salt water must be cover- 
 ed with twenty-four ounce copper. 
 
 Those who have floating docks already constructed Avill be expected to 
 exhibit their powers and mode of operating upon a vessel of suitable size^ 
 which the Department will furnish. 
 
 Proposals must be made by the first day of September. 
 
 A. P. UPSHUR. 
 
 No. 5. 
 
 Navy Department, Septemhtr 10, 1842. 
 Gentlemen: By the act of Congress making appropriations for the 
 Kaval service for the year 1842, it is provided "that the Secretary of the 
 
Doc. Xo. 27. 15^ 
 
 Navy may, in his discretion, apply the sum of one hundred thousand dol- 
 lars of ilic amount hereby appropriated, and any balance of former appro- 
 priations for the construction of a dry dock at Brooklyn, New York, to the 
 construction of a floating dock at the same place ; and if any part of this 
 appropriation shall be expended upon the construction of a floating dock, 
 as hereby auihorized, the construction of the dry dock shall be suspended 
 until the further order of Congress." 
 
 In order to carry out the purposes of Congress, as expressed in this pro- 
 viso, I liave advertised for proposals for constructing floating docks of dif- 
 ferent sizes. I refer you to the enclosed copy of my advertisement, as ex- 
 planatory of my objects and wishes. Many proposals have already been 
 made, and it becomes necessary to institute such a comparison between the 
 several plans as will enable me to lorm a satisfactory judgment in regard 
 to them. You are appointed commissioners for that purpose ; and I have 
 designated the 26th of this month as the time at which the examination 
 will commence in the harbor of New York. Your examinations will em- 
 brace the following principal objects : First, the advantages and disad- 
 vantages of any floating dock, compared with those of an excavated or 
 walled dock ; second, the comparative merits of the several plans of float- 
 ing docks, which may be submitted. Tiie scientific and practical skill and 
 information which you bring to the inquiry will enable you to determine 
 much better than I can to Vv'hat points your attention shall be directed, so 
 that no particular instructions from m.e are necessary. It is enougli for me 
 to say that I wish you to consider the subject in all its bearings, and to 
 make your report as full, and at the same time as minute and particular, 
 as possible. 
 
 You may possibly come to the conclusion that a floating dock may be 
 used advantageously as auxiliary to an excavated dock in New York, or 
 that it may be substituted lor an excavated dock at Pensacola, or other 
 places. If so, you will please report your opinion upon that point. Indeed, 
 as it is the object of the Department to ascertain the utility of the floating 
 dock for the purposes of the navy, under all the circumstances in which it 
 can be brought iiito use, you will be pleased to report any and all facts cal- 
 culated to influence the judgment, as to the propriety of constructing such 
 docks. 
 
 The several persons who have ofiered proposals will be inform.ed that 
 you will be in New York on the 26th instant, and that you will then be 
 ready to proceed with the necessary examinations. 
 
 Should you require to see any of the floating docks in actual operation, 
 Captain Perry will be directed to furnish suitable vessels for that purpose. 
 
 I am respectfully, yours, 
 
 A. P. UPSHUR. 
 
 Capt. B. Kekxon, 
 Samuel Humphreys, Esq. 
 Professor W. R. Johnson. 
 
16 
 
 Doc. No. 27. 
 
 No. 6. 
 
 Report of the commissioners appointed by the Secretary of the Navy to 
 ^examine the several plans of floating docks submitted to the Depart- 
 rnent . 
 
 New York, October 8, 1842. 
 
 Sir : The undersigned, commissioners appointed by you to examine and 
 report upon the several plans of floating docks submitted to the considera- 
 tion of the Department, beg leave to offer the following as the result of 
 their labors : ^ 
 
 At the time designated for meeting the persons who had offered proposals, 
 they repaired to this city, and having, by public notice, acquainted the par- 
 ties interested with the tmie and place of their meeting, proceeded to ex- 
 amine the several plans which were offered for their inspection. 
 
 I<n order to render intelligible what they are about to state in reference 
 to the construction and use of docks, it is deemed not inappropriate to refer 
 to some other methods in general use of placing vessels in a convenient 
 situation for undergoing repairs. 
 
 Besides the well-known method of "heaving ont,'^ by bringing the ves- 
 sel nearly on her beam ends, and thus reaching the keel, the rise and fall 
 of tides afford in some situations sufficient difference between high and 
 low water to bring even large ships on temporary ways at high tide, where 
 they may undergo moderate repairs during the hours of low water. 
 
 In similar situations a dock may be formed, to be opened and closed by 
 gates — the vessel passing in and taking her place at high water, the water 
 receding, and leaving her on proper supports when the tide is out, and the 
 -gates being closed to prevent the entrance of the next tide, and so remain- 
 ing until the repairs are completed. By opening the gates, she may then 
 be allowed to pass out on the first flood tide after the work is finished. 
 
 In a similar manner, instead of erecting a strong permanent dock, a sim- 
 ple machine, much in the form of a scow, with one end opening and closing 
 like a gate, has sometimes been» constructed. At low water, this is allowed 
 to remain at rest in such a situation that, by leaving the gate open, the 
 succeeding high tide will fill it; af'ter which a vessel may be towed into 
 it, and left over suitable supports, till the tide retires, when she will be 
 found completely exposed for inspection and repairs. By closing the gates, 
 the next tide will be excluded, and the scow set afloat. The two preced- 
 ing experiments are of course so much dependant on locality as to height 
 of tides as to be seldom resorted to along our Atlantic coast. 
 
 When naval architecture had reached a considerable degree of perfection, 
 the maritime nations of Europe learned the importance of secure situations 
 in which to make, at leisure, the repairs demanded by the largest class of 
 ships. The first dock erected at Plymouth (England) was in 1655. It 
 was excavated and walled on the plan still uniformly adhered to among 
 the maritime nations of Europe. At Venice, for centuries past, docks have 
 been employed for preserving ships of war until wanted for service. They 
 were often roofed over, as well as the slips on which the vessels were 
 built. It is stated that more than fifty docks and §lips are found in that 
 city. 
 
 In the north of Europe, also, for seventy or eighty years past, many 
 
Doc. No. 27. 
 
 IT 
 
 roofed docks have been used for laying up ships not in commission, as well 
 as for building and repairing them. 
 
 The use of docks at the great naval stations in England has given to 
 those important establishments their distinctive appellation of dock yardsy 
 as the want of docks has, till within a few years, rendered the same de- 
 nomination altogether inapplicable to the navy yards of the United States. 
 
 The terms dt^y and wet docks have grown into use in the great commer- 
 cial ports of England, where the latter are employed for enclosing a large 
 body of water, capable of floating many vessels, and of preserving, by means 
 of gates, a uniform level of water within. This avoids the danger of get- 
 ting aground at low tide, and also secures the convenience of loading and 
 unloading at the same level, subject only to a difference from the variable 
 quantity of cargo on board. 
 
 The dry dock, chiefly confined to repairing vessels, is a structure of much 
 more limited extent, and is so situated as to permit the largest ships which 
 it is intended to receive to enter, if not at all hours, at least at every high 
 -tide. If situated in a port where the tide rises and falls to the amount of 
 the depth of the dock, so that the latter will, become empty at the time of 
 low water, it is evident that no artificial means can be necessary to free it 
 from water when the tide retires. Being suitably supported and shored 
 as the water leaves her, and the gates subsequently closed, the vessel re- 
 mains for any desired length of time without further trouble ; but, if the 
 tide have but a limited range of movement, as at most of the American 
 navy yards, it becomes necessary to exhaust the greater part of the water 
 by artificial means. In constructing the dock, also, the chief part of the 
 work lies far below the level of low water; and hence the necessity of 
 a coffer dam, to keep out the water while such docks are in progress. 
 
 The greatest depth of water requiied in a dry dock is about twenty-seven 
 feet. When relieved of this, should the water without gain admission be- 
 neath the bottom, and there exert its pressure, the force tending to burst or 
 lift the bottom upwards would be more than seventeen hundred pounds 
 ■per square foot. Hence there must be either an exclusion of the water 
 from the under side of the dock, so as to take ofl^" the hydrostatic pressure 
 in that direction, or the bottom must be constructed of materials so dense, 
 and of such thickness, that the weight from the foundation to the upper 
 surface of the bottom shall be equal to that of a column of water from the 
 same foundation to the top of the highest tides. If the bottom be formed 
 of the heaviest granite, of which the specific gravity is nearly three, a thick- 
 ness of about ten feet might answer this condition, especially as the cement 
 possesses strength enough to unite the bottom to the side walls, and di- 
 minish the chance of forcing up the former. If only the weight were avail- 
 able, the thickness must be more than thirteen feet. To sustain the side 
 walls and the closed end of such a dock, which must be nearly or quite forty 
 feet in height, a foundation of the most durable kind must be obtained. In 
 some cases, this has been eff'ected by excavating the dock in part out of 
 solid rock ; but, in others, it could only be done by driving numerous piles, 
 and covering their heads with large beams, crossing these with others, then 
 covering the latter with plank, and laying tlie stone work on this foundation of 
 massive timber. This is one cause of the great expensiveness of an exca- 
 vated and walled dry dock in such situations as that of the Brooklyn navy 
 yard. It is among the causes why the mercantile marine has sought for 
 other and less expensive means for accomplishing its object. But, besides 
 
18 
 
 Doc. No. 27. 
 
 its expensiveness, there are situations where the permanent walled dry 
 dock would be almost useless, from the variableness of height of water from 
 season to season of the year. This would be peculiarly true of the great 
 rivers of the West. A dry dock at Pittsburg, Cincinnati, Louisville, or St.. 
 Louis, must, iu order to be available at all seasons, be at least three or four 
 times as deep as would be necessary to float the ordinary river craft of the 
 Ohio and Mississippi. 
 
 In order to secure despatch in docking and relaunching the steamboats 
 of that part of the country, a floating apparatus, or something equivalent 
 to it, which can adapt its operations to the variable height of the river, is 
 indispensable. 
 
 It was, no doubt, the same expensiveness of the excavated dry dock 
 which induced commercial men to employ all the various substitutes which 
 have of late years been so extensively adopted — such as the marine rail- 
 way, the screw dock, and the hydraulic liftirjg dock, together with the sev- 
 eral forms of floating dock hereafter to be described. All these have been 
 witnessed by the commissioners, and the manner in which commerce avails 
 herself of their aid has been attentively studied. They illustrate, at once, 
 the unbounded resources of the mechanic arts, and the fertile ingenuity of 
 our countrymen, with whom many of these methods of raising ships have 
 originated. 
 
 They may all be most advantageously contrasted with the clumsy expe- 
 dient resorted to at the Plymouth dock yard in 1817, when the 78-gun 
 ship, the Kent, after being completely dismantled, and placed upon sliding 
 planks, was hauled up, against the enormous resistance of friction, upon 
 the ways of a common building slip, by means of 14 capstans, each acting 
 on a threefold purchase, and worked by 2,116 men. 
 
 Even this awkward device would, if applied at this time, and in this 
 country, be vastly improved in character, by substituting anti-attrition 
 metals for bare or merely greased surfaces of timber on the planks and 
 ways. 
 
 Theoretically considered, it must be evident to any one acquainted with 
 the simplest elements of mechanics, that either of the principles on which 
 these substitutes are founded is as capable of being extended to a line-of- 
 hattle ship as to a merchant ship of 500 or 1,000 tons burden. 
 
 By increasing the number of tracks, and securing the solidity of each 
 with corresponding strength in the cradles and trucks of a marine railway 
 by augmenting the number, diameter, and length of the screws in a com- 
 mon lifting screw dock; by enlarging the size and strength of the cylinder 
 and plunger of the hydraulic elevator in that kind of dock; or by adding 
 to the capacity of the caissons or tanks of the floating docks, it is undenia- 
 bly true that power enough may be given to either of these forms of appa- 
 ratus to acGonjplish the entire elevation of the heaviest structure that ever 
 floated on the ocean, and not the dismantled structure only, but fully 
 equipped, with all her masts, rigging, crew, stores, and armament on board. 
 
 The practicability of such an operation was many years since recognised 
 in an English publication* of high authority, in which we find the fol- 
 lowiiig brief description of a wrought-iron moveable caisson, with a rud- 
 der, for docking a ship while riding at her moorings, in any depth of waier^ 
 leaving her keel dry in three hours, without removiris: her stores or masts : 
 
 • Falconer's Marine Diciiouary, edition of 1815. 
 
Doc. No. 27. 
 
 19 
 
 "Tliis caisson, or floating dock, is made of wrought iron, half an inch 
 thick, 220 feet long, 64 feet wide, and 30 feet deep, and will weigh about 
 400 tons, with a stage of 6 feet wide on the top for the workmen to stand 
 on, and also to strengthen the caisson. The weight of this caisson, when 
 immersed in water, is nearly 350 tons, but, for reasons mentioned below, it 
 is rendered nearly buoyant, being surrounded by an air receptacle capable 
 of suspending the whole weight with great exactness, and which is rivetted 
 to it in such a manner as also to strengthen the caisson and support the 
 principal shores from the ship. 
 
 " While light, this caisson will draw nine feet water. When taken to 
 the ship intended to be docked, the water is to be let in at an opening or 
 plug hole in the bottom, and it is to be suffered to sink until the upper part 
 is even with the surface of the water — the air tube still keeping it buoyant. 
 
 " A small quantity of air is then to be discharged by opening a plug 
 hole in the air receptacle, until a quantity of water is let in just sufiicient 
 to sink the caisson below the ship's bottom. This being effected, the 
 caisson (nearly buoyant) is then to be raised to the surface of the water by 
 ropes made fast from the caisson to each quarter of the ship. A pump, 
 placed within the caisson, is then to be worked by a steam engine of twelve- 
 horse power, placed in a barge alongside, which will empty it in three 
 hours, and reduce the draught eight feet water — that is, from twenty-six 
 to eighteen feet, when she may be carried up into shoal water, if required, 
 or along side wharves, or jettee heads of the dock yards. The ship's sides 
 and bottom tending to fall outwards by their own weight, and the sides and 
 bottom of the caisson tending to be forced upwards by the external pres- 
 sure of the water, it is obvious that, by placing props or shores between, 
 both will be supported, while the ship will ride with all her stores on board 
 and masts standing, nearly as easy as when in water. Should inconve- 
 nience be apprehended, at any time, from blowing weather, the caisson may 
 be cast off and let fall to the bottom, where it cannot be injured, and whence 
 it may be raised to the ship's bottom again at pleasure, with as little labor 
 as weighing an anchor. The caisson will be twelve feet above water, 
 when there is a first-rate ship in it. This is a sufficient height to prevent 
 the sea from breaking over. By this plan, a ship may have her bottom 
 examined, and be let out again in six hours. 
 
 From estimation, it has been ascertained that a caisson capable of 
 docking a first-rate ship will not cost above £20,000, and, judging from the 
 duration of wrought iron in salt pans, will last twenty years without re- 
 pairs." 
 
 In none of the floating docks, either proposed or constructed in this 
 country, do we find any thing more simple or more certain in its action 
 than would have been this proposed iron caisson. But a very serious ob- 
 jection to its use, in the form proposed, is the fact that it could be brought 
 under or cast off from the ship only where there was more than double 
 the depth of water which the ship drew. In the case above supposed, of 
 a ship drawing twenty-six feet water, and a caisson thirty feet high, the 
 depth of water where it must be put on or cast off must be at least fifty- 
 six feet. Another circumstance of great importance, in which all the 
 American floating docks differ from the above-described caisson, is in giving 
 far greater breadth than sixty-four feet to a dock destined for ships of the 
 line ; the least of those submitted to our consideration being eighty-five 
 feet, and some extendmg to nearly two hundred feet in breadth. Another 
 
2C 
 
 Doc. No. 27, 
 
 material difference between the caisson and the American docks is, that 
 the latter provide an opening by which the ships enter endwise, and thus 
 require, in addition to their own draught of water, no more than the thick- 
 ness of the bottom of the dock. This was a distinguishing feature in the ' 
 floating dock of Commodore James Barron, of which a working model, 
 now in the Patent Oilice, at Washington, was constructed, and exhibited in 
 action, at Norfolk, many years ago. 
 
 The principle of action of all floating docks is extremely simple. It de- 
 pends on the bulk of water winch the dock displaces, when the weight of 
 the ship is added to its own weight. The mode in which this displacement 
 occurs may be different in the different plans of construction; but, as there 
 is no limit except depth of water and superficial area, it is evident that 
 where these two elements are unlimited, the weight which may be placed 
 on a floating structiu'e of corresponding dimensions and strength must 
 likewise be unlimited. When the form of the dock is that of a prismatic 
 body, like the caisson above described, or like Commodore Barron's dock, 
 or that of Mr. Gilbert, hereafter to be described, the amount of displace- 
 ment, and the consequent depth to which it would sink, is a matter of the 
 simplest calculation. To determine the draught of water of such a dock, 
 either when light or when loaded, we have only to know the area of its 
 horizontal section, and the weight of the dock and ship. Thus, if the 
 length of such a dock be 240 feet, and its breadth 85 I'eet, and if the 
 weight of sea water be takiMi at 64 lbs. per cubic foot, so that 35 cubic feet 
 make a ton, then, for every foot that the dock sinks, it will displace 20,400 
 cubic feet of water, weighing 585 tons; and if we suppose the dock to be 
 so ballasted as to weigh as much as the largest ship of the line, (the 
 Pennsylvania, for example,) with all her rigging, stores, crew, and arma- 
 ment on board, which may be taken at 5,200 tons, then the total weight of 
 dock and ship will be 10,400 tons, and the depth to which it would sink 
 would be 17.77, or say 18 feet. 
 
 Wlien, on the other hand, instead of an enclosed dock to receive the ves- 
 sel, and allow the water to be pumped out from around it, the structure 
 receives the form of a broad trussed platform, with water-tight tanks be- 
 tween the trusses, which may be pumped free of water, after being sunk 
 beneath the bottom of the vessel, then the computation of lifting power 
 will depend on the interior capacity of the tanks — that is, on the v/eight of 
 water which can be withdrawn, to be substituted by an equivalent bulk of 
 air. The submerged timbers of the dock, when the ship has been lifted 
 with her keel quite above the water line, will not then be a matter of any 
 importance, as their density will be so near that of sea water as to render their 
 weight of no amount, and consequently the only weight to be supported 
 will be that of the ship, and of the timbers and machinery of the dock 
 which then lie above water. The principle of computation just stated ap- 
 plies equally to docks built in sections, and to those forming continuous 
 structures. It is evident that, by thus placing the lifting power at some 
 distance below the bottom of the keel, a considerable depth must be given 
 to the truss work — more than would be necessary for the mere support of 
 the ship when resting upon them. 
 
 The number of plans of floating dock which have been submitted to 
 ihe commissioners is seven. 
 
 1. The floating .balance dock of Mr. John S. Gilbert, the vessel resting 
 in the bottom of the dock, and the water kept out by a gate at the end. 
 
Doc. No. 27. 
 
 21 
 
 2. The sectional tank dock of Mr. John Thomas. 
 
 3. The sectional tank dock of the Floating Dry Dock Company of New 
 York. 
 
 4. The sectional floating dock and floating wharves of Mr. Blanchard. 
 
 5. The comhined tank dock of Mr. Von Schmidt, using condensed air 
 to force the water oat of the tanks through holes always open at their 
 "bottoms. 
 
 6. The combined tank dock of Messrs. SchuU and Martin. 
 
 7. The combined or sectional tank dock of Mr. Edward Conover. 
 First. From the above brief enumeration, it will be seen that the dock of 
 
 Mr. Gilbert is the only one which depends on the caisson principle. It is, 
 in fact, constructed with a middle compartment, in which the vessel rests 
 after the water has been pumped out, and two side and one end compart- 
 ments, formed by timbers and planking, sloping outwards from a few feet 
 on each side of the keel blocks towards the upper edge of the sides. 
 These side compartments have therefore the cross section in nearly a tri- 
 angular form, and consequently the inner sloping wall presents facilities 
 for shoring the ve.^sel very similar to those in a walled dry dock. The 
 side chambers allow of the disposition of any desired quantity of ballast 
 to sink the dock, keep low the common centre of gravity of the dock and 
 ship, and so to load the ends of the flooring cross-timbers as to equalize 
 the strain above and below when the ship is in place. They may also 
 retain a quantity of water after the space around the ship has been pumped 
 dry, and, being divided into compartments fore and aft, this water may be 
 so adjusted in the several parts as to preserve the ship in an upright po- 
 sition. 
 
 In a dock 110 feet long and 45 feet wide on the outside, which has been 
 for upwards of two years in use in the North river, and in which, during 
 that time, the owner stated that he had docked between 2.50 and 300 ves- 
 sels of various sizes, the commissioners witnessed the dockinsr and un- 
 docking of a vessel of about 300 tons. The lowering of the dock into 
 the water, by letting fall the gate which moves on a hinge at the bottom, 
 and is so ballasted on the outside as to sink, and the getting in and arranging 
 the position of the vessel, took twenty-five minutes; after which a small 
 four-horse engine was set in motion, and at the end of one hour and thir- 
 ty-five minutes the water was out of the central compartm^ent of the dock, 
 the vessel shored, and the operations on her bottom had been commenced. 
 The only persons employed to assist Mr. Gilbert in this operation were 
 two men and two boys — one of the men being the fireman and engineer, 
 "who attends to all the operations of the machinery. 
 
 The process is so simple, that any person of ordinary capacity could, by 
 seeing it done once, be competent to direct its repetition. 
 
 The lowering of the brig into the water again took about thirty min- 
 utes, and was efl^ected by simply opening and letting fall the gate regu- 
 lating its descent by tackles, after admitting a certain quantity of water 
 through two wickers near its bottom. This operation is, therefore, if pos- 
 sible, still more simple than the other, and scarcely admits of a possible 
 mistake. When the water has risen to a certain height in the middle 
 compartment, gates are opened, to permit it to flow into the side cham- 
 bers, which expedites the sinking of the dock. In construction this dock 
 presents great solidity and strength ; the sides are to be constructed of 
 timber a foot in tliickness to the load line, and six inches above it ; the in- 
 
22 
 
 Doc. No. 27 
 
 terior bracing of the side compartments is most ample, and in a dock for 
 ships of the line the bottom is proposed to be made 3 feet 9 inches thick, 
 of timber, with truss beams 2 feet 9 inches high, on which to place the 
 keel blocks. This thickness of 6^ feet of solid timber under the support 
 of the keel would doubtless constitute a very firm foundation on which 
 to establish the keel blocks, and sustain the weight of the vessel. 
 
 A dock on tins plan, 240 feet long, 85 feet wide, and 33 feet high, cop- 
 pered and copper fastened, has been proposed to be built by Mr. Gil- 
 bert for v^250,000. If built inside of an iron tank, as high as the load line, 
 his proposal is ^10,000 in addition. If chained, felted, and sheathed with 
 boards, the estimate is ^215,000 ; and if without either felting or sheath- 
 ing, ^200,000, according to the accompanying paper, (marked A,) which is 
 herewith submitted. A transverse section of the dock is given in the ac- 
 companying drawing, (marked B,*) and some remarks on the results of 
 experiments on the exhaustion of tanks, by the inventor of the above-de- 
 scribed dock, in the paper marked C. VVithout expressing our assent to 
 all the positions assumed in the last-mentioned paper, we may state our 
 conviction that some of the remarks relative to the two diiferent methods 
 of constructing floating docks are entirely pertinent and just, and, together 
 with the dock which he has in use, evince much discernment and practical 
 tact in the adaptation of simple means to the accomplishment of import- 
 ant ends. 
 
 The advantages and disadvantages of this dock may be summarily 
 stated, as follows : 
 
 The advantages, as compared with other floating docks, are — 
 
 1. The simplicity of construction, and, in consequence of this, 
 
 2. The facility of management, as already ^described. 
 
 3. The great strength which can be given to the* sides, and indeed to 
 all parts of the structure, without impairing its lifting power. 
 
 4. The little depth of water which it demands, beyond what is neces- 
 sary to float the vessel, being only 5 feet 9 inches for a dock to take up 
 ships of 400 tons, and 8 feet for one destined to receive the largest ships 
 of war. 
 
 5. The lowness of the centre of gravity of the whole mass of the ship 
 and dock, the keel not being required to rise, as in all the other floating 
 docks, two or three feet above the level of the water, outside of the dock. 
 
 6. The facility, in consequence of this stable condition of equilibrium, 
 with which the dock may be conveyed from point to point, without en- 
 dangering the structure, even while the vessel is in place, provided a 
 proper advantage be taken of the state of the weather for such re- 
 moval. 
 
 7. The convenience of shoring from the slopes of the side compartments 
 to the sides of the ship, without using props of inconvenient length, and 
 especially of cumbrous weight, the latter increasing more rapidly than 
 the length when a given amount of strength is required in a prop. 
 
 8. The facility with which, by properly ballasting the side tanks, the 
 upward and downward pressures on the bottom of the dock can be equal- 
 ized so as not to bend or unduly strain the bottom. 
 
 The disadvantages, as compared with other floating docks, are — 
 
 1. It does not afford so much free space in which to work as most other 
 floating docks. 
 
 2. It does not bring the vessel entirely above the level of surrounding; 
 
Doc. No. ti7 
 
 23 
 
 obstacles, so as to give a strong light on every part of the bottom. This 
 objection is, however, less weighty in Mr. Gilbert's dock than in one which, 
 is excavated and walled. 
 
 3. It cannot receive more than one vessel at a time, which is another dis- 
 advantage which it has in common with the permanent dry dock. 
 
 Mr. Gilbert has stated that he could, without increasing the cost of his 
 dock, add 5 feet to the breadth, making it, in all, 90 feet wide. This would 
 increase the stability by about one-ninth, and the lifting power by one- 
 seventeenth of the amount above supposed. It would also allow larger 
 side compartments in which considerable quantities of water might be oc- 
 <)asionally left to aid the ballast in keeping the dock lower in the water than 
 it would otherwise lie. This would keep the centre of gravity of the ship, 
 it is true, nearer the level of the water than before, but the centre of grav- 
 ity of the dock and its contents would be raised nearly in the same pro- 
 portion by placing masses of water high up the sides; so that, as a measure 
 to obtain stability, it might not be found essentially useful. 
 
 Second. The dock of Mr. John Thomas is constructed in sections, each about 
 -^3 feet wide, S5 feet long, and 9 feet deep, with tanks within the whole, to 
 contain 21,400 cubic feet of water, weighing 611 tons. Seven such sections, 
 making a total length of 231 feet, and a total Ufting power of 4,277 tons, 
 are proposed to be joined together, to form a dock for ships of the line. The 
 €nds of this dock being entirely open, and the upright sides being also open 
 frames, the vessel must of course be lifted entirely above water level. Al- 
 lowing for the usual height of keel blocks two feet, there will be demanded 
 by this dock at least 11 feet of Avater, in addition to the draught of the ship 
 to be docked. Thus a depth of 36 feet of water would be requisite to dock 
 a ship of the line drawing 25 feet. Mr. Thomas preserves the stability of 
 his dock by means of floating wharves extending the whole length on each, 
 side, and connected by chains passing over pulleys, with projecting timbers 
 Teaching beyond the upright frame work of each section. By means of 
 weights attached to the opposite ends of the chains, the wharves may be 
 made to serve the purpose of buoying up any desired portion of the weight 
 of the dock. The machinery for pumping out the sections was not exhibited, 
 nor was it stated whether the working of the several sections was to be 
 simultaneous and equable or not. The inventor is understood to have em- 
 ployed a dock on his plan, for several years, at St. Louis, on the Missis- 
 sippi, taking up steamboats of all sizes. As the principle of Mr. Thomas 
 is embraced, together with some additions by others, in the dock next to be 
 described, it will not be necessary to state separately its advantages and 
 disadvantages. The paper marked K is a letter from Mr. Thomas, giving 
 information in regard to the construction of his dock. 
 
 Third. The commissioners were enabled to study the subject of sectional 
 floating docks in a practical way at the establishment of the floating dry 
 "dock, foot of Rutgers street. East river, where the plan is in daily operation. 
 The dock there erected is in seven sections, each 93 feet in the extreme 
 length, 24 leet in breadth, and 11 feet 3 inches in depth. This depth, 
 added to two feet in the height of keel blocks and of the lower timbers, 
 makes the depth of water necessary to use it 15 feet greater than that 
 of the ship to be docked. The submerged tanks of a section contain 
 10,100 cubic feet, or 283 tons of salt water. Two buoyant tanks, one at 
 each end of the section, 20 feet long, 10 wide, and 7 deep, are capable ot 
 idisplacing each 40 tons of water. These, with the submerged tanks, will 
 
24 
 
 Doc. No. 27. 
 
 therefore exert a maximum lifting power of 363 tons. The company use 
 the seven sections at present in two docks — one composed of five sections^ 
 for taking up large ships and steamboats, and the other of two sections, for 
 docking smaller vessels. 
 
 The operation of docking consists in first lowering the docks to a suffi- 
 cient depth, according to the draught of the vessel. This is effected by rais- 
 ing, with the aid of a sleam-engine placed on the top of one of the sections 
 on each side of the dock, the buoyant side tanks of all the sections. Their 
 weight, together with the ballast which they contain, is sufficient to sink 
 the dock. A line of shafting, running horizontally from section to section, 
 causes all to move with the same speed ; and the strong cast-iron racks at- 
 tached to two upright posts of the sections effectually suspend the tanks at 
 any desired level and keep down the dock. When it has been lowered to 
 a sufficient depth, the engines are §topped, the ship is brought in, and, by 
 means of gauges on the horizontal wale shores, placed on both sides, is ad- 
 justed wuh her keel directly over the blocks. The pumps which exhaust 
 the water from the submerged tanks are then put into uniform action in all 
 the sections, and the consequent rising of the dock soon brings the blocks in 
 contact with the keel. Bilge blocks, sliding on cross-timbers over the floor 
 of the dock, are then drawn forward by ropes until they come in contact 
 with the lower part of the vessel. The pumping then goes on until the 
 floor of the dock is wholly above the level of the water, and the bottom of 
 the keel of course about 2i feet higher. 
 
 The performance witnessed by the commissioners was that of the five- 
 section dock employed in taking up the Metoka, a merchant ship, of which 
 the custom-house register of tonnage was stated to be 776 tons. In this; 
 case, the time employed to sink the dock was 25 minutes ; to bring in and 
 adjust the position of the ship took five minutes. Her draught of water, in 
 consequence of having 200 tons of ballast on board, was a little more than 
 10 feet. The lifting continued 3 hours 22^ minutes, so that the whole time 
 employed in preparing and docking this vessel was 4 hours 38^ minutes. 
 The engines are of 8-horse power each, and, during the time the vessel is 
 rising, are employed either successively or simultaneously on the pumps, 
 and m depressing the floating side tanks. In the early stages of the pro- 
 cess, as the water had to be pumped out against a superincumbent head of 
 13 or 14 feet, the two operations were alternate. In the latter part of the 
 time, they were occasionally both carried on together. 
 
 It should be mentioned that the operations of the workmen on the bot^ 
 tom of the ship were commenced 30 or 40 minutes before the engines stop- 
 ped, the remainder of the time being taken up in getting the dock floor some 
 inches above the level of the water, and accurately trimming the ship in 
 due position. There are required in docking a vessel on this plan one prin- 
 cipal engineer, who usually occupies the deck of the ship, two steam-en- 
 gine tenders, and two hands on each side of the vessel to manage and ad- 
 just the wale shores. In about 24 hours the vessel had been freed from 
 the foulness with which she came out of the water, and completely copper- 
 ed. The commissioners then witnessed the process of lowering her into 
 the water, which commences by opening gates in the lower part of the sub- 
 merged tanks through tubes which descend from the top of the side frames- 
 in the engine room on each section. The steam-engine is also put in mo- 
 tion, to raise the side tanks, which might otherwise be carried wholly under 
 water. By the gauge marks on every section, the engineer on the deck of 
 
Doc. No. 27. 
 
 25 
 
 the ship, by passing from side to side, observes whether the descent is uni- 
 form in all parts, and directs the persons managing the gates to increase or 
 diminish the flow accordingly. When the vessel has been in part brought 
 to rest in the water, the danger of deranging her position by allowing the 
 water to flow too rapidly into any one tank is so much lessened that the 
 gates are opened to their full extent, and the side tanks raised pretty rapid- 
 ly, 10 allow the dock to sink readily and set the ship afloat. The lowering 
 of the Metoka took just 40 minutes. This dock is understood to have been- 
 in operation for about eighteen months, and to have taken up from 100 to 
 200 vessels of various sizes. Under the discreet and skilful management 
 of the ingenious mechanics by whom it was designed and constructed, it has 
 continued to perform its work successfully, without accidents, as we were 
 assured, and without requiring any outlay for repairs. The ample breadth 
 of the dock (65 feet between the upright side frames) enables it to take up 
 two small vessels at a time, instead of a single large one, so that when ar- 
 ranged, as at present, in two docks, three, and even four vessels may be 
 undergoing repairs at a time. To take up long steamboats, the whole seven 
 <*« sections are put in requisition to constitute one dock. The two-section dock, 
 as at present used, is pumped and worked wholly by hand. Tiie floating 
 side tanks are raised and lowered by means of a square vertical shaft com- 
 ing down from the engine room above and moving a level wheel which is 
 attached to a frame on the tank, and sets in motion a system of tangents, 
 screws, wheels, and pinions, which connect the tank with the tooth-rack al- 
 ready referred to. Tiie amount of machinery thus required to raise and 
 lo wer the tanks and to work the pumps is, in the present docks, stated to 
 be about two tons on each side of the section. 
 
 A part of this machinery remains constantly near the level of the water,, 
 while the rest rises as the dock rises. The latter is of course the case with 
 the steam-engines, boilers, kc. 
 
 The mode of constructing and propping the interior of the tanks was ex- 
 plained, and that of trussing the sectional frames was exhibited by pump- 
 ing out one or two sections until they came to draw not more than three or 
 four feet of water. 
 
 This dock, which, as stated by one of the proprietors, embraces the plans 
 
 of J. Thomas, Wash & Williams, Mitchell, together with those of 
 
 Dodge & Burgess, was greatly admired for its ingenuity, which reflects much 
 credit on the constructor, himself one of the inventors, by whom the several 
 elements were combined in a manner to produce the efl^ects above de- 
 scribed. 
 
 The dock which this company proposes to construct for the Government 
 is planned with an extreme breadth of 137 feet, with two submerged tanks 
 in each section, each 45 feet long, 18 feet wide, and 10^ feet deep, clear in- 
 ternal capacity, independent of the props and cross-timbers of the insides. 
 The capacity of such tanks will be equal to 489 tons of sea water. The 
 two side tanks are proposed to be 20 feet square and 8 feet deep, so that 
 their total displacement will be 188 tons, giving the maximum buoyancy 
 of a section 677 tons, and for eight sections of 24 feet each, sufficient to oc- 
 cupy the length of keel (195 feet) of a line of battle ship, will be 5,416 tons. 
 The part of the dock and of the machinery out of water, when the ship is 
 raised, is estimated at 65 tons to a section, or for eight sections, 520 tons. 
 This added to 5,200 tons, the assum.ed weight of the Pennsylvania, makes 
 the weight to be hfted 5,720 tons, about 300 tons more than the calculated 
 
26 
 
 Doc. No. 27. 
 
 power of the dock, supposing it pumped entirely dry. By making the sub- 
 merged tanks 11.5 deep in the clear, and the side tanks the same as above, 
 the buoyancy would be 5,760 tons, (gross,) and, by increasing the side tanks 
 to the same depth as the submerged ones, the whole power would be 6,358, 
 or 638 tons more than the weight to be sustained, which, considering the 
 construction, is certainly not an excess. 
 
 We will now proceed to state what appear to us to be the advantages 
 and disadvantages of this dock. 
 
 Its advantages are — 
 
 1. That of adapting itself in some degree to the form of the keel. The 
 commissioners do not attach great importance to this feature, since every 
 other form of dock which they have witnessed has some equivalent method 
 of adjusting the supports to the form assumed by the keel when afloat. 
 
 2. As it takes a vessel entirely above the water level, and as its ends 
 are open and only a moderate quantity of frame work is placed on the 
 sides, there is an abundance of light and air. 
 
 3. It is capable of being elongated or contracted, to suit the length of the 
 vessel to be docked, thus saving a portion of time and labor in pumping 
 out a large dock to raise a small ship. The two-section dock, above refer- 
 red to, has a greater length than the breadth of the two sections which it 
 receives by means of a temporary plattorm of planks and keel timbers, ex- 
 tending from one to the other some 15 or 20 feet. 
 
 4. In consequence of being separable into sections, the whole dock may 
 be conveyed, if necessary, to a distance through narrow channels. The 
 supposed utility of this feature,set forth by the proprietors, could not, how- 
 ever, be available in conveying a Government dock through a canal, since- 
 the length of 137 feet is believed to be greater than that of any locks in 
 the country. 
 
 5. It is capable of being repaired in sections by taking out one at a time 
 on the tops of high blocks placed on the floors of the rest. In other words, 
 a section may be docked just as a ship would be in its place, or a new 
 section may be built to replace one found to be worn out. 
 
 In the accompanying paper marked D, the president of the company, 
 Mr. S. D. Dakin, has set forth several other supposed advantages ; to 
 which, however, the commissioners do not attach the same importance as 
 is claimed by the writer, and some of the positions they think wholly un- 
 tenable, especially those which relate to the waterlogging of the dock and 
 its behavior when acted on by waves. 
 
 The disadvantages of this dock are — 
 
 1. It has the buoyant power at the bottom wholly below the weight 
 which it is to carry, thereby rendering additional machinery, in the form of 
 buoying tanks, and a great breadth of the structure, necessary. Without 
 these, the equilibrium would be essentially unstable, like that of a vessel 
 carrying a deck load without ballast in her hold. 
 
 2. The draught of water is very considerable. Fifteen feet below the 
 bottom of the keel of a ship of the line would amount to 40 feet in all — a 
 depth believed not to be attainable at any of the navy yards in the United 
 States without artificial excavation. This objection may, it is true, apply 
 in some degree to all floating docks, but especially so to those which 
 place the buoyant power beneath the vessel to be raised. To get rid of 
 ihis, an increase of breadth becomes inevitable. 
 
Doc. No. 27. 
 
 27 
 
 3. The tanks being by their construction independent of the frame work 
 which they support, and capable of being drawn out as occasion requires* 
 they must possess a strength which that frame does nothing to afford, in. 
 order to resist the enormous pressure brought upon them when the water 
 first begins to be pumped out at a great depth, amounting ip fact to 12 or 
 13 pounds per square inch when the tank is 28 feet below the water. This 
 Joads the upper surface of the two tanks in a section to the extent of nearly 
 1,300 tons in such a dock as the company propose to build for the Govern- 
 ment, while its true lifting power, when the dock comes to the surface, 
 would be less than half that amount. Hence it is evident that the prop- 
 ping must be very substantial. 
 
 4. As it lifts thfe ship high up into the air, it affords full exposure of her 
 broadsides, masts, spars, and rigging to the action of the wind. The 
 <jentre of figure of a longhudinal vertical section of such a ship as the 
 Pennsylvania will be higher than her centre of gravity. The area of that 
 section is 11,760 square feet; and, in order to convey some idea of the 
 influence which winds of different degrees of velocity might produce, tend- 
 ing to displace the ship when thus elevated, the following table has been, 
 calculated. The side surface of dock below the keel is left out of the ac- 
 count. 
 
 Character of the wind in respect to force. 
 
 Velocity in feet 
 per second. 
 
 Velocity in 
 
 miles 
 per hour. 
 
 • 
 
 Pressure exerted on 
 the broadside of a 
 ship of the line in. 
 tons. 
 
 1. A brisk breeze 
 
 20 
 
 13.6 
 
 4.8 
 
 2. A very brisk breeze 
 
 30 
 
 19.5 
 
 10.34 
 
 3. A high wind 
 
 50 
 
 34.1 
 
 26.89 
 
 4. A very high wind - 
 
 70 
 
 47.7 
 
 58.79 
 
 5. A storm or tempest 
 
 80 
 
 54.5 
 
 76.85 
 
 ^. A great storm 
 
 100 
 
 68.2 
 
 120.08 
 
 7. A hurricane 
 
 120 
 
 S1.8 
 
 172.86 
 
 8. A violent hurricane, such as 
 
 
 
 
 tears up trees 
 
 150 
 
 102.3 
 
 270 
 
 To calculate the effect of the last-mentioned wind, admitting that the 
 masts and spars produce an etfect equal to one-tenth of the hull, we should 
 have in all 297 tons apphed opposite to her centre of figure, at the height 
 of more than 28.5 feet above the keel. As the dock is supposed incapable 
 of moving sidewise, the moment of force, therefore, tending to turn the ship 
 on her keel as an axis, will be 297x28.5=8,464.5 tons applied at the dis- 
 tance of one foot. The sustaining force tending to resist this overturning 
 is the strength of the props acting on the buoyancy of the side tanks. 
 These latter will apply their resistance at the distance of 56 feet from the 
 centre of the dock. We find that the force tending to depress the leeward 
 side of the dock, when apphed at that distance, will be 151 tons; and as 
 the buoyant power to resist it is to be derived from 8 floating tanks, each 
 
28 
 
 Dec. No. 27 
 
 20 feet square on the base, the whole effect of sinking one foot is to dis- 
 place 3,200 cubic feet of water, weighing 91.5 tons. If this be supposed, 
 the only resistance to careening the dock might, on the leeward side, be 
 depressed 1.65 feet, or 20 inches; and the line of direction from the centre 
 of gravity will be carried about 8« inches to leeward of the centre of the 
 keel. This is the calculation of an extreme case, it is true ; but if a ship 
 were to remain some months upon the dock, it would be by no means un- 
 worthy of consideration. The upright, with sliding tiebands fastened to 
 the piers, according to the prcvsent arrangements of the company, wouldy 
 in a measure, counteract this tendency to inclination, and the consequent 
 rocking motion ; but the tendency would remain, and be felt to a certain 
 extent. 
 
 5. A still more serious disadvantage of this dock is the complex nature 
 of the structure, and the consequent skill and caution required in its man- 
 agement. In tlie hands of those who feel the naturally deep interest of in- 
 ventors in its success, and who use it daily, it works without difficulty; but, 
 if used by those who should be only occasionally called upon, and especi> 
 ally by those who should for the first time attempt to dock or undock a 
 ship, it is easy to foresee that much embarrassment might occur. 
 
 6. The great length of props demanded for properly shoring a large 
 vessel on a plane horizontal surface is an objection to this, in common with 
 other docks constructed on similar principles. 
 
 7. The great breadth which this dock would occupy, and at the Brook- 
 lyn navy«yard the great extent of excavation which would be required in 
 order to afford it a berth, would be serious inconveniences. Its breadth 
 would be 47 feet greater than that of Mr. Gilbert, and its depth at least 7 
 feet greater from the tops of the keel blocks to the bottom timbers of the 
 dock. 
 
 8. Its expensiveness is stated to be $88 per ton, of capacity for any 
 amount under 4,500 tons ; and this, for a dock of 5,200 tons, would bring 
 the dock alone to ^457,600, about half the amount of the lowest estimate 
 of a walled dock. If nothing were charged for the power beyond 4,500 
 tons, it would still cost ^396^000 at the rate proposed. This is $136,000 
 more than the highest estimate of Mr. Gilbert. It does not include the 
 preparation of a site. The accompanying letter (marked E) from Mr. 
 Dakin proposes to prepare the site, build two piers, (of piles,) with a crib 
 of stone at the end of each, and form a floating boom to protect the en- 
 trance, for the sum of $13,000. It is the opinion of the commissioners,, 
 that, in order to render such piers permanent, a much greater sum would 
 be required. 
 
 Fourth. The sectional floating dock and floating wharves of Mr. Blanchard 
 are essentially dependent on the same principle as the two precedingo 
 Tanks are placed under the ship, out of which the water is to be pumped 
 by an engine elevated far above the floor of the dock ; the two ends of the 
 section are made to rise equably by an iron shaft traversing the top of the 
 tank, under the floor of the dock, and having a pinion at each end, to take 
 hold of a vertical rack in the timbers connected with the two floating 
 wharves. The two wharves are connected together by timbers going 
 down as low as the tanks are ever to sink, and are tied by cross-timbers at 
 the bottom, and at a certain distance up. There is a lattice truss in the in- 
 terior of the tanks, and the sides of the tanks themselves are formed of tim- 
 
Doc No. 27, 
 
 29 
 
 bers which constitute a species of truss. By these expedients, the support 
 for the ship and that to sustain the inward pressure on the tanks, when ex- 
 hausted far below the surface of the water, are in a manner combined. 
 No specifications having accompanied the model of Mr. Bianchard, it is 
 not necessary to enter into an examination of its advantages or disadvan- 
 tages. Nearly all the objections already stated against the two preceding 
 docks would equally apply to this. 
 
 Fifth. The combuied tank dock of Mr. P^ter Von Schmidt, called the 
 " floating pneumatic dock.'' The model first exhibited to the commission- 
 ers by the inventor had cylindrical tanks arranged and lying horizontally 
 at the bottom of a frame work. At the lower side of each was an opening, 
 to allow a free passage of water into and out of the tank. Into the upper 
 part of each entered a small tube, connected with a metallic cylindrical res- 
 ervoir of highly condensed air, forced into it by an air syringe of the usual 
 form. The ship being brought over the dock, the several connecting stop-* 
 cocks were turned, and the air rushing into the tanks, and driving the water 
 through the openings in their bottoms, rendered the whole structure buoy- 
 ant, raising the ship above the level of the water. The great and fatal ob- 
 jection, in the minds of the commissioners, to the principle of obtaining 
 buoyancy for this dock, by means of condensed air, is, in their view, suffi- 
 cient to decide against its adoption. The difficulty of obtaining wooden, 
 and even metallic boxes, which will retain air for a great length of time in 
 a state of compression, is a fact familiar to all who have had occasion to 
 make the experiment; and, even supposing the tanks made perfectly air- 
 tight at first, they could not be secured in that degree of tightness for any 
 length of time, as, on the cylindrical-tank model, a dock for a ship of the 
 Jme would have required 43 feet of water. Mr. Schmidt subsequently 
 presented the accompanying drawing F, the specification G, and the esti- 
 mate H, wliich will sufficiently explain the views of the inventor, but do 
 #ot remove any of the essential objections, except that against the draught 
 of water. ' 
 
 Sixth. The combined tank dock connected with permanent piers, in^ 
 vented by Messrs. Schulland Martin. This dock depends, in part, for its 
 lifting power on the exhaustion of tanks, and in part on the lifting power 
 of machinery established on the permanent piers at the sides of the dock, 
 the latter being intended to preserve the stability of the dock. 
 
 If established on a lake or inland sea of invariable height, this dock 
 might possibly fulfil its design ; but where the tide rises and falls, the ma- 
 chinery of rack-work and pinions would be liable to speedy derangement. 
 
 Besides this fatal objection, the dock requires 48 feet of water to place it 
 in order to take on a ship of the line — nearly double as much as the aver- 
 age depth in the channel near the navy yard at Brooklyn. It is not intend- 
 ed to deny that, with proper solidity of piers, and with strength and mas- 
 siveness of machinery, a dock might be constructed which, without the aid. 
 -of any buoyant tanks, might lift a ship of the line : but the character of a 
 floating dock would be merged, and the expensiveness of a walled perma- 
 nent dock would be, if not equalled, at least pretty nearly approximated, 
 without attaining the permanency desired in ail works of a national char- 
 acter. The paper marked I is a statement from Mr. W. A. Cox, relative 
 io the construction and advantages of this dock. 
 
 Seventh. The model of a floating dock, stated to have been invented and 
 
30 
 
 Doc. No. 27. 
 
 patented 18 years ago, was exhibited to the commission by IVIr. Edward Con- 
 over. Large tanks to contain water were represented as established on solid 
 piers at the sides of the dock, at the height of 25 or 30 feet above the level 
 of water in the basin. These were to be pumped full of water. At the 
 bottom of the dock were empty water-tight tanks, to be forced down low 
 enough to receive the vessel. This was done by filling a set of tanks along 
 the top of the dock, sustained on strong upright timbers. Water was to be 
 allowed to flow from the permanent water tanks on the piers, in quantity 
 equal to the weight of the ship and dock. This would sink the air tanks. 
 The ship was then to be brought on the tops of the latter, and the moveable 
 "water tanks were to be allowed to empty their contents through gates or 
 stop cocks into the basin below, and allow the air tanks to elevate the ship. 
 This dock has never been brought into use, and the above description will 
 probably suggest a sufficient explanation of that fact. 
 
 Having thus gone through with an account of the character, advantages, 
 and disadvantages of the several plans of floating docks, compared with 
 each other, as required by your ^e^-o^zr/ direction, we are in a condition to 
 offer some definite views in regard to the first query, viz : " Jidvantetges 
 and disadvantages of any floating dock, as compared with those of an 
 excavated or walled dock.^' 
 
 The advantages are — 
 
 1. The smallness of the original cost, the estimates varying, for the two 
 principal plans now in use in this city, from ^200,000 to S396,000, exclu- 
 sive of the preparation of a site, while the excavated or walled dock may 
 cost, according to diff'erent estimates, from ^900,000 to 1,200,000. 
 
 The preparation of a site, excavating, building piers, forming protecting 
 booms, niust largely enhance the above estimates for a floating dock, as al- 
 ready suggested. 
 
 2. The short time required to build the floating dock — six or eight months 
 being the time assigned by several of the persons offering to undertake i% 
 and as many years being generally allotted to the construction of a walled 
 dock. If the Government were at war, and had, in' the harbor of New 
 York, several disabled vessels, wiiich could not make their way either to 
 Charlestown or to Norfolk, and the question was, the most speedy method of 
 getting docked, it would doubtless render this consideration important, in- 
 dependent of the loss of interest or cost between the commencement and 
 the completion of a walled dock. Such is not, however, the situation of the 
 Government. If ever built for an emergency like that supposed, the sim- 
 plest form should be preferred. 
 
 3. More space may be generally allowed for working, with a better light 
 and less humid air. 
 
 4. They take all vessp.ls up from the level at which they float, and da 
 not, like the walled dock, carry even the smallest craft down to the same 
 blocks on which the keel of a ship of the line must rest, and they require 
 a proportionately less labor, as the draught of water is less. This advan- 
 tage is of but little practical importance in the naval service. 
 
 5. The sectional floating docks can take up more than one small vessel 
 at a time. Where a dock is used to earn profit to its owners, this may be 
 of much importance ; but the urgency of naval requisitions can seldom give 
 it any importance at our navy yards. Indeed, if our present dry docks 
 could have all the vessels wanting repairs in the navy brought to their 
 
Doc. No. 27. 
 
 31 
 
 gates, it is believed there could seldom occur much delay in one vessel wait- . 
 ing for another. 
 
 The disadvantaqes of the floating docks are — 
 
 1. Their perishable nature, being liable to decay, to conflagration, and 
 to damage from violent gales of wind. The copper with which they might 
 be covered would be liable to speedy corrosion, especially at the Brooklyn 
 navy yard, where it is represented that the gases rising from the mud are 
 particularly injurious to sheathing copper. 
 
 2. The great surface and depth of water which they require, rendering 
 it imperative to excavate a hole or well over which to place the floating 
 dock at the Brooklyn navy yard, before any one of the proposed floating 
 docks could be brought into action on a large ship. The accompanying pa-- 
 per (marked L) contains notes, furnished by Captain Perry, in relation to the 
 width and depth of channel at the navy yard, Brooklyn. 
 
 3. The great risk of placing a large heavy ship for weeks or months on a 
 buoyant platform for extensive repairs, with the possibility that such repairs 
 might be suspended for want of appropriations, or from other causes. Such 
 repairs not unfrequently require several strakes of plank to be removed, or 
 part of a keel to be taken out ; and it is not often convenient to force the 
 completion of such work by hiring extra hands, but it nmst be done by the 
 force in employ at the yard. The placing of so much public property as a 
 large national vessel in so hazardous a situation as that just referred ta 
 could not but be deemed an act of temerity. 
 
 4. If placed between piers, and not effectually secured against chafing, 
 the copper might be worn off" in spots and admit the worms, which, in such 
 a harbor as tltat of Pensacola, would soon destroy the timber of a floating 
 dock. 
 
 5. Designing persons might, unless it were strictly guarded, easily per- 
 forate the sides of a floating dock just below the water level, and thus let 
 in water to one side, or to one or more of the buoyant tanks,- of a floating 
 section dock, even through the copper which has been proposed to be put 
 upon them. With a large ship on the dock, and her planking partly off,, 
 such an occurrence would lead to serious consequences. 
 
 6. The floating docks are, without exception, more difficult to manage 
 than a walled dock, as the latter require no nice attention to the adjust- 
 ment of level. If trimmed, when she goes into a walled dock, the vessel 
 can be at once shored against the solid walls in such a manner as to defy 
 all accidents. This does not in any degree depend on the greater or less 
 rapidity of pumping out water from one or another part of the dock, as all 
 is pumped out from the same part. 
 
 If not a substitute for the wailed dock, we cannot regard the floating 
 dock important as an auxiliary at the Brooklyn navy yard, since, if a per- 
 manent dock be erected there at all, it will be adequate to all the repairs 
 which the Government are likely to have occasion for at that station. 
 
 In addition to all the other objections to a floating dock for Pensacola, 
 it may be mentioned that the temperature of the climate at that place 
 would cause a more speedy decay of the timbers than in the harbor of 
 New York. For naval purposes a permanent walled dock is deemed 
 preferable to all others, being at all times available, and never liable, like 
 every floating dock, to be found out of repair. 
 
 Should any sudden emergency hereafter require the erection of a tem-- 
 porary substitute for a walled dock, the foregoing statements will sufli- 
 
32 
 
 Doc. Jfo. 27. 
 
 ciently point to the balance dock'^ of Mr. Gilbert as the one which your 
 commissioners decidedly prefer, on account of its simplicity, solidity, stable 
 position, and ample buoyant power — in short, for its nearer approxima- 
 tion than any other to the character of that for which it would be a sub- 
 stitute, namely, the walled dock. If built in a wrought-iron tank, as he 
 has proposed, and suitably galvanized to defend it from corrosion, the 
 chances of injury, either from accident or design, would doubtless be greatly 
 diminished. 
 
 Having thus given to the subject as full, minute, and particular exami- 
 nation as the case seemed to demand, we have only to submit the result 
 to your hands, with the assurances of our most respectful consideration. 
 
 BEVERLY KENNON, 
 
 Captain U. S. Navy. 
 SAMUEL HUMPHREYS, 
 WALTER R. JOHNSON. 
 
 Hon. a. p. Upshur, 
 
 Secretary of the Navy. 
 
 A. 
 
 New York, October, 1842. 
 
 Gentlemen : Herewith are transmitted proposals for building a floating 
 dry dock on my plan, called the " floating balance,'^ of sufficient strength, 
 and capacity to dock the ship of war Pennsylvania, weighing 5,200 tons. 
 For proposals in the proper form, I would respectfully refer to my propo- 
 sals sent in on the 1st of last September to the Navy Department, agreeably 
 to the advertisements of the Secretary of the Navy. 
 
 I would also refer the commission to the accompanying description for 
 explanation for the methods of constructing, upon which the prices are 
 based. 
 
 For a floating balance dock, coppered and copper fastened, 
 
 the sum of - ^250,000 
 
 For a floating balance dock, built inside of an iron scow, the 
 
 sum of ------ - 260,000 
 
 For a floating balance dock, charred, felted, and sheathed, 
 
 the sum of ----- - 215,000 
 
 For a floating balance dock, without either felting or sheath- 
 ing, the sum of - - - - - - 200,000 
 
 My understanding the commission to specify that 5,200 is the required 
 strength and lifting power of the dock, has caused me to shghtly vary my 
 price from my proposals now in the Navy Department. 
 
 JOHN S. GILBERT, 
 
 Capt. Kennon, 
 Co!. Humphreys, 
 Prof. W. R. Johnson, 
 
 Comrnission on Dry Docks, 
 
Doc. No. 27. 
 
 33 
 
 Length of dock, out to out - - 
 l^readth « . - . . 
 
 Depth c - . . . 
 
 Thickness of bottom - 
 Thickness of sides to load b'ne 
 Thickness of sides above 
 
 Truss beams, sufficient, by actual trial by hy- 
 drauUc press, to sustain 
 
 Thickness of bottom - - - 
 
 Truss beams - - - - - 
 
 Keel block - - 
 
 Cap pieces, to split out - - - - 
 
 240 feet inches. 
 90 " " 
 
 a 9 u 
 
 " 3 top sides. 
 
 33 
 3 
 1 
 6 
 
 5,200 tons. 
 
 3 feet 9 inches. 
 2 9 " 
 1 « " 
 « 6 " 
 
 
 
 Gentlemen : After two years' experience in docking vessels, I now re- 
 spectfully give my opinion on the subject of my balance dry dock. 
 
 I believe a floating dock on my plan, eighty-five feet wide, and two hun- 
 dred and forty feet long, loaded with sufficient ballast to sink it with all 
 gates open, would have sufficient stability throughout the entire operation 
 of docking and undocking the ship Pennsylvania in any weather, even if 
 the centre of gravity of the dock and vessel, considered as one body, should 
 be above the water line, because the distance from the keel of the vessel to 
 the end of the lever (or side of the dock) would be nearly as great as from 
 her keel to her spar-deck, and the draught of the dock would be fifteen 
 feet ; this would give an average pressure against the sides of four hun- 
 dred and eighty pounds to every square foot. 
 
 In case the wind should blow very hard, and the least danger was ap- 
 prehended, water may be let into the side camels, and the dock settled 
 down ; this would make the dock more stiff, and at the same time leave 
 the dock dry for the workmen. 
 
 I find that I can dock a vessel when the sea runs high, because the waves 
 cannot escape at the sides or at the solid end ; and before they can back 
 out, others heave in, and keep the vessel from striking upon the blocks. 
 
 It is generally believed that timber, well charred, may remain under 
 water many years without being touched by worms. I would therefore 
 respectfully suggest that the bottom of a floating dock may be burned, and 
 then covered with felt and sheathing, so as to be secure from worms as long 
 as the dock would last ; but, for the port of New York, no sheathing of 
 copper, iron, or wood, is at all necessary, because, if the dock is floated into 
 fresh water once in two or three years, the worms will be destroyed. This 
 may be done by a Government steamer in ten hours, by floating it up the 
 Hudson river ; or it maybe done for ^250 up, and the same amount down, 
 by a private steamer, and the same course may be taken where there is a 
 fresh water river near. 
 
 I would ask the attention of the commission to my mode of constructing 
 my balance dock as far up as the load line. In the first place, lay an entire 
 thickness of timber crossways, and caulk the upper side with wedges. I 
 then build up the sides and ends of thick timber, bolting one course or 
 streak on to another, and caulk these seams also with wedges. I then lay 
 
 3 
 
34 
 
 Doc. No. 27. 
 
 a thickness of limber on the bottom, fore and aft, and caulk it with wedges, 
 and then another thickness crossways,and caulk that also with wedges ; in- 
 side of this scow, 1 build my dock. It will be seen, therefore, that I build 
 from the inside, and, of course, all repairs must be made from the inside. 
 
 In regard to resheathing or recoppering the under side of the bottom, 
 my plan is, to remove all the ballast, and put across a few temporary deck 
 beams and stanchions under them to stiffen the dock, and then fill one 
 side of the dock with water. This would careen the dock so as to get at 
 least a part of the bottom ; but in any place where there is five feet rise 
 and fall of water, string pieces may be laid parallel to the shore, and the 
 copper or sheathing laid upon these string pieces ; they should incline in 
 the width of the dock five feet. Water is then let into one side of the 
 dock to cant it, and in this way it may be floated on to the ways, and cop- 
 pered, by tides, half way down, and then floated and turned the other side 
 to the shore. But the plan which has always seemed best to me is, to 
 build an iron scow, and then build the dock inside of it. I would here 
 state, that no danger need be apprehended from worms on the inside, as 
 salt water will stagnate in twelve hours when there is but a small quantity 
 in the dock, and in that state the worms immediately die. 
 
 Another method has been suggested to me, which is, to lay ways, with 
 a channel in them for common balls, and haul the dock entirely out of 
 water. 
 
 In my explanations before the commission, I believe I neglected to men- 
 lion that I do not pump the water from around a vessel in my dock when 
 she is less than one hundred and fifty tons ; for, when I dock a vessel of 
 that weight or less, I pump the water out of the side chambers, and, as the 
 dock rises, the water ebbs out at the wicket gates. And a frigate may be 
 raised nearly out of the water by the power of the chambers, when in a dock 
 large enough for a ship of the line : thus much time is saved. Although the 
 sides are thirty-three feet high, the openings are made to extend down to 
 near the load line of the dock, and these gates are made to shut over the 
 openings in bad weather. 
 
 JOHN S. GILBERT. 
 
 Capt. Kennon, 
 Col. Humphreys, 
 Prof. W. R. Johnson, 
 
 Commission on Dry Docks. 
 
 [Here follows a diagram, marked B, in the original ] 
 
 c. 
 
 Gentlemen : Having been assured, by the honorable the Secretary of 
 the Navy, that a full opportunity would be afl'orded me to lay all the in- 
 formation which I had collected and obtained, by experiments, before the 
 commission which would examine floating dry docks, I take this method 
 of presenting an outline of the n suits of actual experiments made by me 
 from about t)ie year 18i;!5 up to tl is time. 
 
 About the year 182'5, a floating dock was built in this city. I witnessed 
 the first attempt to dock a vessel in it, but it went lo pieces on its first trial. 
 
Doc. No. 27. 
 
 35 
 
 Jt was evident to me that the failure of that project was owing to the en- 
 tire ignorance of the inventor. The sciences involved in the constructioa 
 of a machine that has its centre of gravity so far removed by the intro- 
 duction of a weight into it in the form of a ship have a wide range; but 
 I am satisfied there are but two methods of applying the floating principle 
 to the purpose of raising ships out of water : by one method, the ship is 
 raised out of water on the tops of exhausted tanks, which is like loading 
 a* ship on deck and leaving her hold empty ; by the other method, the 
 ship is floated into an enclosure, and raised out of water by pumping the 
 water from around her. This is like putting the cargo into the ship's hold. 
 
 The following are the characteristics of the tank or sectional floating 
 docks; and my object is to draw your attention, in order that the positions 
 "may be examined at your leisure. 
 
 The philosophical objections to a sectional tank dock are as follows : 
 Firstly. The natural lifting power of water is exerted in an exact per- 
 pendicular direction. If the sides of a nearly exhausted tank, which is held 
 under water by a load on its top, cannot, in the slightest degree, form a 
 perpendicular line, the keel block at the lower end receives less support than 
 its due, and what is lost at that block is doubled at the block at the 
 opposite end. The tendency of the pressure is to the highest point ; therefore 
 there is no reliable support to the ship at any other point than the one keel 
 block at tlie highest point of the tank ; the consequence is, that a ship that 
 is crooked when taken on that dock always continues to crook, so that the 
 philosophy is borne out by practical results. The larger the tank the more 
 serious the result. 
 
 Secondly. In all harbors along the seaboard, there is a swelling of the 
 water called ^ ground swell ; the action of this swell is deep. A dock 
 formed of sections does undulate, and, even with the ordinary swell, raised 
 by the wind acting on the upper or end tanks, causes undulatioi>; for these 
 end tanks must have displacement enough to keep the dock from capsizing, 
 and, as they rise with the crown of the sea, and drop into the hollow, un- 
 dulation follows as a law of nature. Again philosophy is sustained by 
 practical experience. 
 
 Thirdly. The weight of the ship is borne on the top of the dock. The 
 centre of gravity, therefore, is higher, by about the entire draught of the 
 ship, than it would be if she rested on the bottom of the dock. 
 
 The mechanical objections are — 
 
 Firstly. In order to equipoise the superincumbent weight of a ship, great 
 width is necessary ; it cannot be extended, with satisfactory results, without 
 at the same time increasing the depth of the framing, for the strength of 
 the truss framing depends much upon the angle of the braces, truss framing 
 depends entirely upon the bands, and they will decrease in strength about 
 ten per cent, per aimum. 
 
 Secondly. It is practically impossible to make two pumps that will ex- 
 haust the same quantity in a given time ; and, if it were, it would be impos- 
 sible to distribute the weight of the ship on a number of separate sections, 
 so that she would be supported according to model or sectional weight. 
 
 Thirdly. When a sectional tank dock is sunk for a reception of a ship of 
 the line, there will be near two thousand pounds pressure upon every square 
 foot of surface. As soon as the pumps are set to work, they do not rise at first 
 in the same proportion to tiie number of cubic feet of water discharged as at 
 last, inasmuch as the water leaving the vessel brings the greatest weight on 
 
36 
 
 Doc. No. 27 
 
 at first ; therefore, much of air or buoyant space will be filled with the ne- 
 cessary braces, to enable the tanks to sustain the pressure ; for, if the cavity 
 of the tank is not supported, the hydrostatic pressure upon them when they 
 are exhausted will cause them to contract, and again expand ; when they 
 are filled, this wiW cause them to leak, and, as they act separately, one may 
 settle down, and consequently strain the ship. 
 
 Fourthly. The lifting and balancing power are entirely separate in their 
 action; the end or balancing tanks are entirely dependent upon cog wheels; 
 therefore, the breaking of one cog would endanger both deck and ship. 
 
 Fifthly. The sectional tank dock must draw about twice as much water, 
 when in the operation of docking a ship, as the ship draws. 
 
 Sixthly. There are no rests for shoring a ship in the sectional tank dock ; 
 bilge chacks give but little support to the frame of a ship. 
 
 Seventhly. A tank dock cannot be coppered without using copper truss 
 bands ; for iron is soon eat out by copper, and it is questionable whether 
 sufficient strength could be obtained by using copper bands. 
 
 Eighthly. In a tank dock, the power that lifts the dock and vessel acts 
 first upon all sides of the tanks; they again act upon the framing. Thus the 
 strength of tanks does not in any way assist the frames on which the vessel 
 rests ; therefore, the strength of the whole dock does not act upon the vessel 
 iti a combined form. 
 
 The above are the results of actual experiments. 
 
 JOHN S. GILBERT. 
 
 Captain B. Kennon, United States Navy, 
 Colonel S. Humphreys, Naval Architect. 
 Mr. W. R. Johnson. 
 
 SECTIONAL FLOATING DRY DOCK. 
 
 Points of superiority claimed by the sectional floating dry dock over 
 
 every other kind of dry dock. 
 
 1st. It presents a pliant, flexible platform, capable of being made of any 
 required strength by trussing, which conforms, as soon as the vessel is 
 brought to its bearing, to the shape of the keel and bottom; and, as it is 
 upheld itself by the upward pressure of the water, it presses upon the bot- 
 tom of the vessel like the water itself, affording a definite, equable, hm- 
 ited, and entirely controllable strain upon the various parts of the keel 
 and sides at a great variety of points, and entirely preventing the injuries 
 so common, and indeed unavoidable, on other docks, in consequence of the 
 difficulty of laying the keel blocks (which must be laid by guess) upon a 
 rigid platform, so as to be in the exact line of the keel as it floats; thus 
 forcing it to conform to a false line, bringing the whole weight of the ves- 
 sel to one point, cutting through the keel blocks, and straining the timbers 
 and plank throughout the whole hull. 
 
 2d. It brings the vessel's bottom up fully into the light and air, instead 
 of plunging her down, as other docks do, into a narrow, dark, wet, and 
 unwholesome hole ; and thus enables the shipwright to do the work much 
 
Doc. No. 27. 
 
 37 
 
 cheaper, better, and more agreeably, and to save ail the old copper mate- 
 rials on its broad, clear, and well-lighted platform. 
 
 3d. It is capable of expansion and contraction, according to the length of 
 the vessel, and is divisible into two or more separate docks, each perfect 
 in itself; so that one on our plan, built for the smaller class of vessels, is 
 adapted by simply building additional sections on to it, to be extended so 
 as to raise the largest ship of the line — the small dock thus constituting a 
 part of the large one, and saving the necessity of distinct expenditures for 
 each ; and, also, when built to the extent requisite for a ship of the line, 
 the whole structure is not required, as in the stone dock and other floating 
 docks, to take up a single small vessel, but, by its sectional arrangement, 
 it is capable of being instantly divided into two or more separate docks or 
 berths, to raise two or more smaller vessels at the same time, as two frig- 
 ates, or one frigate and two or more vessels of an inferior class. A stone 
 dock or a floating camel dock can take out but one vessel at a time, how- 
 ever small. We can take out six schooners or brigs at a time on our 
 seven sections. 
 
 4th. Each section of our dock acts independently, yet all act in concert, 
 to accomplish the object in hand ; each section has a limited lifting power, 
 and yields in the water as soon as that power is exhausted, if pressed be- 
 yond it, without taking or giving any additional strain; and by the ar- 
 rangement of cutting up the structure into sections, and requiring each 
 section to bear only a limited amount of strain, to which it is adapted, and 
 making them all accomplish their work by a kind of division of labor, we 
 are enabled, not only to make a given amount of timber and iron exert 
 its strength in the most efficient and economical manner, but to secure it 
 against the contingency of an overwhelming strain bearing upon any one 
 point. Hence, we can construct our dock of great width and length with- 
 out impairing its strength. Hence, also, our dock is peculiarly fitted to re- 
 ceive the wide and long war steamers, which, in consequence of their 
 heavy machinery and delicate structure, it is particularly desirable to hold 
 nearly as they float. This we are enabled to do by exhausting from 
 the tanks of each section just as much water as the part of the steamer im- 
 mediately over the section displaces when afloat ; thus substituting for 
 the one pressure another precisely equivalent. But, as the floating camel 
 dock is an inflexible structure, it is not possible to endue it, if of large size, 
 with sufficient strength to sustain vessels of great weight, or to sustain the 
 strain at the ends of the upward pressure of water, if made long enough 
 for a steamer, when a short heavy ship lies on its central portion, even 
 with the most skilful trussing, and much less without. Neither is it possi- 
 ble to construct the gates of a sufficient strength to bear the pressure of a 
 wide deep column of water, such as must press against them if large enough 
 to admit a line-of-battle ship, as their abutments cannot be trussed, and, at 
 best, can aflEbrd but a frail support, which must be torn away under the 
 strain, and destroy the structure. 
 
 5th. It is easily moveable from place to place — an advantage of some 
 moment in case of an anticipated attack on the navy yard by the enemy, 
 inasmuch as, in such an event, the dock m^ight be sunk in deep water, out 
 of reach, and raised again when the danger was over, or it might be towed 
 by steamboats to a place of entire safety. This is an advantage which our 
 dock possesses over a stone dock, in common with other floating docks; 
 but our sectional floating dock possesses an advantage over the camel 
 
38 
 
 Doc. No. 27. 
 
 floating dock, by being moveable in sections. In case, for instance, one 
 should be built for the navy yard at Brooklyn, and afterwards a stone dock 
 should be deemed necessary, and the Government should desire to send 
 the former to Philadelphia, it could be towed in sections, through the Dela- 
 ware and Raritan canal, to that city. 
 
 6th. It saves a great amount of expense in taking out a ship for repairs, 
 the raising of the largest line-of-battle ship costing but a few dollars, and 
 the expense decreasing as the size of the vessel diminishes ; whereas, in a 
 stone dock and camel dock, not only is the expense for a large ship greater, 
 but it increases as the size of the vessel diminishes. 
 
 7th. It can be completed to the largest size in a few months, (not more 
 than eight or ten at most,) ready for use ; whereas it will take several 
 years, at a vastly greater expense, to finish a stone dock ; and it is believed 
 that the interest accruing on the money that would be expended on the 
 latter, before it could be used at all, would nearly, if not quite, pay for the 
 former, and in adcjlition furnish means to the Government for repairing 
 vessels in the mean time. The result would therefore be, speaking com- 
 paratively, and supposing the floating dock to supersede, as we believe it 
 will, the necessity of a stone dock, that the floating dock would virtually 
 cost nothing, or, in other words, would be built by the money that would 
 be lost in interest in building a stone dock, before the latter could be used 
 at all, and would, in addition, furnish means of repairing vessels, of which 
 the Government would otherwise, in the mean time, be destitute. 
 
 8th. It is easily taken out of the water in sections, to be repaired, one 
 section being raised on two others for that purpose ; but the camel dock, 
 though much more liable than the sectional dock to get out of repair, in 
 consequence of the immense strain on its inflexible platform, is absolutely 
 incapable of being repaired in any manner whatever. 
 
 9th. It is entirely independent of the tides, and a vessel is raised on it 
 equally well in high or low water. 
 
 10th. The camel dock is afifected very sensibly by the undulation of the 
 waves, though perhaps not very injuriously, being acted upon by them as 
 the vessel itself is when lying in the water ; but the sectional dock, when 
 occupied hy a vessel, is entirely unaffected by the agitation of the water, and 
 must necessarily be so by the very laws of nature. Let us suppose a vessel 
 raised on li, wholly above the surface of the w;a/er, with the lifting structure 
 beneath it, by displacing a quantity of water precisely equal to the weight » 
 of the vessel, it is apparent that the platform, with its tanks, liea in the 
 water precisely as if it was what is technically called waterlogged, its 
 whole buoya.nt power being exhausted by upholding the vessel ; the tim- 
 bers that connect the sections, being keyed as soon as the vessel is raised, 
 cannot move separately any longer, but become one firm structure ; and 
 the swell of the harbor, which never rufiles the water to half the depth oc- 
 cupied by these quasi waterlogged sections, washes harmlessly over them, 
 and instantly dies against them, for want of water to supply its action in 
 the space now occupied by the timbers and tanks ; and the end floats are 
 equally unaffected by the swell, because, though their buoyancy is only in 
 part exhausted, and they lie on the water only slightly pressed therein, yet 
 each acts like a lever at each end of each section, with the vessel's keel as 
 a fulcrum, counteracting each other, if acted on extraneously by the swell 
 or any other disturbing force, and each instantly resisting any disturbance 
 the other may be exposed to receive. It is a fact that, during the heaviest 
 
Doc. No. 27. 
 
 39 
 
 gales, vessels have uniformly lain on the sectional dock without the slight- 
 est motion, or the least variation of the masts from a vertical line, and con* 
 fessedly safer than at a solid pier. 
 
 11th. Our company have extended their structure to seven sections, of 
 300 tons each, making a lifting power of over 2.000 tons, and more than 
 double that of any other elevating dry dock in the country, and capable of 
 raising a frigate even now ; and in case the Government adopts our plan, 
 the Navy Department could be prepared, as soon as they have completed 
 two or three sections, by union with five or six of our sections, which could 
 be easily effected, to take out a 74-gun ship. 
 
 12th. Ours is the only floating dry dock that Ras ever been practically 
 extended to a capacity of raising vessels of the first class, and it is the only 
 one that has been absolutely known experimentally to have succeeded on 
 a large scale. 
 
 13th. In case of a leak springing in our dock, it is not probable that this 
 could happen to but one section at a time, (and it has never yet occurred 
 in our dock at all,) and there is always reserved power enough in the 
 others to dispense with one altogether; so the result would therefore be, 
 that, in case the leak could not be stopped or counteracted by pumping, 
 the sections being all keyed together, and the water remaining in the other 
 tanks being pumped out, the power lost is immediately supplied, and the 
 vessel is kept in position. In the camel dock, if a leak should occur be- 
 yond the capacity of the pumps to counteract, the whole structure must 
 inevitably sink. 
 
 It is to be remarked, that the platform which supports the vessel, and 
 which constitutes about seven-eighths of the cost of the whole structure, is 
 constantly under water, and is consequently almost imperishable ; and the 
 work is so framed that the timbers and fixtures above the water can be 
 supplied when decayed, and easily affixed to the platform. 
 
 It is to be remarked, that this sectional dock has been in constant and 
 successful operation for nearly two years, and the register of the dock ex- 
 hibits a list of several hundred sailing vessels and steamers which have 
 been repaired on it during that period without the slightest accident or in- 
 jury either to the dock or a vessel in a single instance — a fact which pre- 
 sents the best possible evidence of the safety of the dock. 
 
 It is also to be remarked, that the steamboats Albany and De Witt Clinton, 
 which are about 64 feet wide and about 300 feet long,were raised recently 
 on six sections of this dock, and their owners (Mr. Stevens and Mr. Dun- 
 lap, ^themselves skilful mechanics and sound practical men) most unhesi- 
 tatingly declare that, though they never before had those boats raised 
 without serious strain and injury, they were taken out by our dock without 
 the slightest strain or injury, even to the most delicate fixtures. 
 
 We can appeal most confidently to nine-tenths of the shipwrights in the 
 city, and to all who are not interested directly or indirectly in the old- 
 fashioned plans of dry docks, for confirmation of our claims to superiority 
 over other plans of dry docks, and to sustain us in every position above 
 taken on the subject. 
 
 L. D. DAKIN. 
 
40 
 
 Doc. No. 27 
 
 E. 
 
 John S. Dakiji^s letter relative to the cost of constructing a site for a 
 floating dock, Sfc, at Brooklyn, Long Island, 
 
 N Ew York, October 4, 1842. 
 
 Gentlemen: I am authorized by Messrs. Campbell & Moody, a very 
 respectable and responsible firm in this city, to say to you that they arc 
 ready to contract with the Government to excavate a berth or location for 
 a sectional floating dry dock, on our plan, at the navy yard at Brooklyn, 
 any where in the vicinity of the proposed location of the stone dock, to the 
 depth of 40 feet, in every respect adequate to work a dock of 5,500 tons 
 capacity, for the sum oi four thousand doW^x^ ; and also to build two piers, 
 one each side of the excavation, with a crib of stone abutment at the end 
 of each, and each thirty (30) feet wide, and 250 feet long, and similar in 
 construction to the piers on the East river in New York, for four thousand 
 five hundred dollars each, with a protecting boom in front, and with close 
 piles driven at the sides, to prevent the influx of the mud. 
 
 Under these circumstances, I am ready, in behalf of our company, to 
 contract for the said excavation and piers at the same rate, and to agree 
 that the whole cost of berth, piers, and location, in every respect adequate 
 for working the dock at Brooklyn, for the sum of thirteen thousand dol- 
 lars. 
 
 This proposition is made upon thorough examination of the proposed 
 location, and accurate calculations of the expenses; and we are fully pre- 
 pared to make this a part and parcel of our proposals to Government. 
 
 I would add, also, that should the Government purchase the small gore 
 of land between Jackson street and the navy yard, as has been contem- 
 plated by the Secretary of the Navy, it will afford a location for the dock, 
 with abundance of water, without any dredging ; and the current of water 
 at that point will always preserve the requisite depth. 
 
 Respectfully, yours, 
 
 S. D. DAKIN. 
 
 Messrs. Kennon, ^ 
 
 Humphreys, and > Commissioners, <5'C. 
 Johnson, ) 
 
 [Here follows diagram, marked F, in the original.] 
 
 G. 
 
 Description of a floating pneumatic dry dock, by Peter Vor^ 
 
 Schmidt. 
 
 The elevating power of this dock consists in a series of submerged air- 
 chambe rs of a square (or they may be cylindrical) shape, underlying the 
 whole frame work, and so connected with it as that each separate cham- 
 ber may be detached and withdrawn for repair, at pleasure, the cubical 
 contents of the whole exceeding the amount of the displacement of water 
 
Doc. No. 27. 
 
 4t 
 
 by the dock itself, and the vessel to be raised, by such an amount as will 
 ensure the dock and vessel against all ordinary contingencies. 
 
 These chambers are air-tight, excepting at the bottom, where are one or 
 more holes to each, for the admission and discharge of water, and of a size 
 sufficient for the easy entrance of a man. They are designed to be con- 
 structed of four-inch stuff on the top, three-inch stutfon the sides, and two- 
 inch stulf at the bottom, each side bolted together, through and through, 
 with iron rods of § inch diameter, (or |-inch copper rods, as may be ])re- 
 ferred;) both ends of the rods are countersunk, and covered with prepared 
 wooden pUigs, or other suitable material, for cutting off the access of the 
 water. The stuff of which the chambers are made is all charred, and im- 
 pregnated with a preparation that will effectually secure the wood against 
 the attack of the worms, and also its greater durability. The connecting 
 rods are placed at intervals of every four feet ; whilst at the intermediate 
 central distances the chambers rest against the timbers of the dock, so that 
 they are supported at intervals of every two feet. The lines of chambers 
 run transversely of the dock. In each line are six chambers, each of 33' 
 feet length, 10 feet width, and 5 feet depth, from out to out. 
 
 There are also on each side of the dock six upright elevating cylinders, 
 (or square chambers may be used instead,) the top of which is on a level 
 with the upper frame work, and the lower extremity of which is entirely 
 open — extends to the lower tier of the timbers. 
 
 They are of eight feet diameter in the clear, and serve as elevators, in the 
 same manner as the submerged air chambers. 
 
 There are also air-tight supporting cylinders (or square chambers may 
 be used instead) between the upright elevating cylinders, which always 
 lie on the surface of the water, and, when the dock is raised, are fastened 
 in their places by cross-timbers. They serve to prevent the dock from 
 rolling, by the action of the winds or waves. The ballast (which may 
 most conveniently be of large stone) is laid upon the outward part of the 
 frame work, or on the top of the air chambers. This plan is adopted in- 
 stead of ballast boxes, as originally designed, and as in the model exhibited 
 to the commissioners in New York, in order to save the space occupied by 
 the boxes for elevating purposes. 
 
 For raising the dock, air is pumped into the submerged air chambers 
 and the upright cylinders, through copper tubes of suitable dimensions, by- 
 means of a steam engine, working one or a dozen air pumps, as may be 
 desired. Each tube connects with a series of chambers, and is supplied 
 with two cocks, one for admitting and the other for discharging the air ; 
 and there are valves so arranged as to cut off the passage of air from one 
 series of chambers to another. The air pumps, the cocks, &c., are all in 
 the engineer's room on the top of the dock, subject to his sole use, always 
 secured against the action of the elements. 
 
 The dock is constructed principally of small timber, so framed, braced, 
 and fastened with bolts, (to be of copper under the water lines,) as to be 
 capable of resisting any strain to which it would be liable. That part of 
 the frame on which the vessel rests is put together so firmly that the dock 
 will not be liable to settle in the centre. The frame work all being open^ 
 neither high winds nor a heavy sea would cause it to rock, so as to endan- 
 ger a vessel on the ways. * 
 
 When a vessel is floated into the dock, she is adjusted so as to bring her 
 keel to the centre, by means of wires or cables stretched across the fram© 
 
42 
 
 Doc. No. 27. 
 
 work, and attached to it, with the centre marked upon them. She is then 
 secured in her position, by fastening these wires or cables suitably to her 
 when the dock is raised. 
 
 ' There are permanent keel blocks for the two extremities of the keel first 
 to rest upon. As soon as these are touched, the admission of air is shut 
 off, and sliding keel blocks, wedged-shaped, are then drawn from each side 
 by means of chains or ropes, and windlass, at intervals of every four feet ; 
 so that the ship rests upon her keel, maintaining her form as when afloat. 
 At the same time the shores, which also move in slides by means of chains 
 and windlass, fastened by ratchets, are drawn up to the vessel. The rais- 
 ing is then completed. 
 
 The shores are constructed of permanent frame work, and projecting 
 therefrom are scaflbld timbers. On these the necessary plank can be laid, 
 without loss of time, and work proceed on the whole bottom simultane- 
 ously. 
 
 In the engineer's room are spirit levels, which indicate the position in 
 which the dock is rising, and which will govern him in the admission of 
 air into any series of chambers. In like manner, they serve to regulate the 
 sinking of the dock. 
 
 The capacity of the dock, for which the accompanying estimates and 
 proposals are made, is given on the estimates. 
 
 In the event of war, a disabled vessel could be taken out of harm's way 
 by this dock, with little liability to injury itself. Twenty chambers might 
 be injured by shells or balls, without materially affecting its sustaining 
 power. 
 
 Three hands would be sufficient to attend a dock of the largest size, viz : 
 an engineer, an assistant to attend the cocks, and a hand to manage the 
 keel blocks and shores. 
 
 The dock can be built and ready for use in six months. 
 
 This dock,being one solid structure, will not subject a vessel to strain by 
 its own action. 
 
 An advantage claimed in the use of air pumps is, that they are not as 
 liable to derangement as water pumps, nor to freezing in the winter season. 
 
 No time is lost by this dock in the erection of scaffolds. 
 
 Abundant open space is afforded around the ship for the employment of 
 a large number of hands, where great speed is required, and also for man- 
 aging bulky timber, where repairs requiring it are needed. This will be 
 distinctly perceived on reference to the drawing. 
 
 The width of the dock is such that the centre of gravity of the whole 
 mass is brought so near to the surface of the water that there can be no 
 danger of capsizing. In addition to this, the supporting cylinders at the 
 sides, which are only brought into action by a side inclination of the dock, 
 serve to increase the improbability of such an occurrence. 
 
 With regard to the material use for impregnating the submerged timber 
 and planks, satisfactory evidence will be given to the commissioners of its 
 efficacy to the end proposed, on their application. 
 
 It is not perhaps necessary, at this time, to divulge the information. It 
 is proper, also, to say that, in charring the surface of the timber and plank, 
 the process employed is such as to accomplish this object without the least 
 possibility of damage to the mass. 
 
 PETER VON SCHMIDT. 
 
 New York, October 6, 1842. 
 
Doc. No. 27. 
 
 43 
 
 H. 
 
 Mr. Von Schmidt's description and estimates for his dry dock. 
 
 Wrought Irok, at 12^ cents p^r pound, work in- 
 cluded. 
 
 132 hoops for 12 cylinders ; each cylinder to be 40 
 feet long, 8 feet diameter in the clear ; every 4 
 feet a hoop, or 11 hoops to a cylinder; the iron 
 to be 2 inches wide, and ^ inch thick ; each hoop 
 in three parts, connected by wedges. 
 
 Formula: 324''x2''X <>-5"x 1 1 X 12-^1,728x480 
 lbs. X 12.5 lbs. . - - . 
 
 12 iron head bars. 
 
 Formula: 114"X 2"x0.5"x 12-4- 1,728 X 480 X 
 12.5 cents - - _ _ - 
 
 160 hoops to 16 support cylinders, 10 hoops each; 
 dimensions as above. 
 
 Formula : 324" X 2" X 0- 5" X 1 X 1 6-4- 1 , 728 X 480 
 X 12.5 cents - - - - - 
 
 32 head bars. 
 
 Formula: 114''x 2"xO-5''X 32-4-1,728 x480x 
 12.5 cents - - - . . 
 
 40 ratish bars to keep the scaffolds ; shores, station- 
 ary, 15 feet each. 
 
 Formula: 180"x3"x l"X40-^l,728x480x 12.5 
 cents ---__> 
 
 40 ketsher to the ratshes. 
 
 Formula : 1 2" X 3" X 3" X 40-4- 1 , 728 x 480 X 1 2. 5 
 cents 
 
 1,000 screw bolts |, to scaffold shores.' 
 
 Formula : 6" x 0. 3068' X 1 , 000-;- 1, 728 X 1 4 cents 
 
 1,404 screw bolts f , to the upper part of boxes. 
 
 Formula: 120"x0.3068"x 1,404_4-I,728x4ti0x 
 14 cents - _ _ . _ 
 
 2,808 screw bolts to the sides of same boxes. 
 
 Formula : 66'' x 0.3068" X 2,808-4- 1 ,728 x 480 X 14 
 cents 
 
 Total wrought iron - - - _ 
 
 Copper, at 30 cents^er pound. 
 2,862 screw bolts f , to connect framing. 
 Formula : 6"x0.3068"x2,862-4-l,728x544x30 
 cents 
 
 1,762 screw bolts on main timber, 1 inch dist. 
 Formula: 9"x0-'7853"x 1,762-4-1,728x544x30 
 cents 
 
 €21 screw bolts, to connect upper and lower sleep- 
 er, 1st. 
 
 Formula : 84" x 0. 7853" X 621-4-1,728 X 544 x 30 
 cents 
 
 648 bands on main timber. 
 
 Formula : 72"(average) x2"x0.5"x648-4-l,728 
 X 544x30 cents - - - * - 
 
 540 screw bolts |, to fasten the box sleepers to the 
 joists. 
 
 Formula : 1 8" X 0. 3068" X 540-7- 1 , 728 X 544 x 30 
 cents 
 
 Total copper - - - - . 
 
 Pounds. 
 
 11,856 
 360 
 
 14,400 
 1,008 
 
 6,000 
 
 1,200 
 508.8 
 
 14,352 
 
 15,888 
 
 65,572.8 
 
 1,632 
 3,916.8 
 
 12,892 
 14,688 
 
 941.1 
 34,069.1 
 
 Cubic 
 feet. 
 
 24.7 
 0.78 
 
 30 
 2.1 
 
 12.5 
 
 2.5 
 1.06 
 
 29.9 
 
 33.1 
 
 Tons. 
 
 136.61 
 
 7.2 
 
 23.7 
 
 27 
 
 1.75 
 
 62.63 
 
 5.9 
 
 0.18 
 
 7.2 
 
 0.5 
 
 0.6 
 0.25 
 
 7.9 
 
 32.53 
 
 0.8 
 
 1.9 
 
 6.4 
 
 7.3 
 
 0.47 
 
 16.87 
 
 Dollars. 
 
 1,482 00 
 45 00 
 
 1,800 00 
 126 00 
 
 750 00 
 
 150 00 
 70 23 
 
 2,009 28 
 
 2,224 32 
 
 8,656 88 
 
 489 60 
 
 1,175 OO 
 
 3,867 84 
 
 4,406 40 
 
 282 33 
 
 10,221 18 
 
44 
 
 Doc. No. 27. 
 
 H — Continued. 
 
 TIMBER. 
 
 Cubic feet. 
 
 Square feet. 
 
 Dollars. 
 
 156 boxes, each 33 feet long, 10 feet wide, and 5 feet deep; 
 
 
 
 
 
 the upper plank 4". 
 Formula : 33' X 1 0' X 4^'' X ^ 50 X 'I t'ents - - - 
 
 
 
 
 
 16,500 
 
 198,000 
 
 7,920 
 
 00 
 
 Formula: lO'x l98X3''X26x4 cents, 3'' thick, (side 
 
 
 
 plank) -.___> 
 
 9,646 
 
 154,440 
 
 6,177 OO 
 
 Formula: lO'x ^98x2''x26x4 cents, bottom of boxes 
 
 8,586 
 
 102,960 
 
 4,118 
 
 40 
 
 312 heads of said boxes. 
 
 
 
 
 Formula: 10'X5'X3"X 12x26x4 cents 
 
 3,900 
 
 46,800 
 
 192 
 
 00 
 
 12 upright c^'linders, open below, 40' long, 8 feet diame- 
 
 
 
 ter in the clear, 3 inch staff. 
 
 
 
 
 
 Formula: 26. 7x3" X 40x12 X 4 cents - 
 
 3,204 
 
 38,448 
 
 1,537 
 
 92 
 
 12 cylinder heads. 
 
 
 
 Formula: 26.7x2.125x3"x ^2x4 cents " 
 
 160 
 
 2,042.5 
 
 81 
 
 70 
 
 16 sup. cylinders, 25' long, dimensions as before. 
 
 
 
 
 Formula: 26.7x25 X 3" X 16x4 cents - 
 
 267 
 
 3,204 
 
 1,281 
 
 64 
 
 32 cylinder heads. 
 
 
 
 
 Formula: 26. 7x2. 125x3"x32x4 cents 
 
 453.8 
 
 5,446.7 
 
 217 
 
 84 
 
 Main timber, 2.5 (average width) by 6". 
 
 
 
 
 Formula: 1 98' X 2. 5 x 6" X 27x4 cents 
 
 6,682 
 
 80,190 
 
 3,207 60 
 
 Upper sill?, 12 to be 198' long, and 15, 182 feet. 
 
 
 
 Istformula: 198' xl'X 6^X12x4 cents 
 
 1,187 
 
 14,256 
 
 570 
 
 24 
 
 2d formula: 182'xl'x6"x 15x4 cents 
 
 1,365 
 
 16,380 
 
 655 
 
 20 
 
 Lower sills, 1 98' X 0. 5 x 6" X 27 X 4 cents 
 
 1,336 
 
 16,038 
 
 641 
 
 00 
 
 Timber in upper frame work. 
 
 
 
 
 Formula: 314'x6'^X3"xl2x4 cents - 
 
 471 
 
 5,652 
 
 226 
 
 08 
 
 Formula : 264x6" X 3" X 15x4 cents - - - 
 
 495 
 
 5,940 
 
 237 
 
 60 
 
 Formula: Posts, I,903'x0.5'x3"x 27x4 cents 
 
 6.422 
 
 77,071 
 
 3,082 
 
 86 
 
 Formula: Bracing, 1, 200' X 4" x 3" X 27x4 cents 
 
 2,700 
 
 32,400 
 
 1,296 
 
 OO 
 
 Formula: Keel beam, 260'x2'Xl'x4 cents 
 
 520 
 
 6,240 
 
 249 
 
 60 
 
 Formula : Upper sleepers, 260 X 9" X 4" X 48 X 4 cents - 
 
 3,120 
 
 37,440 
 
 1,497 
 
 60 
 
 Formula: Lower sleepers, 260x0.5x4x23x4 cents - 
 
 996 
 
 11,960 
 
 478 
 
 40 
 
 Connecting timber. 
 
 
 
 
 
 Formula: 260x0. 5x3" X 42x4 cents - 
 
 1,365 
 
 16,380 
 
 655 
 
 20 
 
 Formula: Lengthwise bracing, 698x0.5x3"x 12x4cts. 
 
 1,047 
 
 12,564 
 
 502 
 
 56 
 
 Trnn Vipfwnpn fmmp wArlr 
 
 
 
 
 
 Formula: 6, 240x0. 5x3" X 4 cents - - - 
 
 780 
 
 9,360 
 
 374 40 
 
 Keel shores, every 4 feet. 
 
 
 
 
 r urmuia . lox^^X" X X* cenis - - - 
 
 909 
 
 >if 'toy/ 
 
 97 
 
 20 
 
 Formula: Shore frames, 90 xO. 5 x 3" X 12x4 cents 
 
 135 
 
 1,620 
 
 64 
 
 80 
 
 Formula: 1st scaffold shores, 421 x 0.5x3" x 44x4 cents 
 
 2,315 
 
 27,786 
 
 1,111 
 
 44 
 
 r ormula : 2d scaffold shores, 195 x 0. 5 x 3" X 44 x 4 cents 
 
 107 
 
 12,870 
 
 514 
 
 80 
 
 Formula: — sleides frames, 90 X 0.5 x 3" X 50x4 cents 
 
 56 
 
 6,750 
 
 270 
 
 00 
 
 
 74,017.8 
 
 993,489.2 
 
 37,258 
 
 42 
 
 Add 75 per cent, for work - 
 
 
 
 27,943 
 
 81 
 
 Total timber and work - - - - - 
 
 
 
 65,202 
 
 23 
 
 1 
 
Doc. No. 2T. 
 
 45 
 
 RECAPITULATION. 
 
 Timber for work, 993,489 square feet - - - - - 65,202 23 
 
 Iron and work, 32.53 tons - - - - - - ' - $8,65f? 88 
 
 Copper and work, 16.87 tons - . - - ^ - - 10,221 17 
 
 84,080 28 
 
 Copper pumps, cocks, and valves, &c. ------ 2,000 00 
 
 Steam engine - - - - - - - - - 5,000 00 
 
 91,080 28 
 
 Add 10 per cent, for contingencies ------ 9,108 02 
 
 Total ---------- 100.188 30 
 
 The total weight of the dry dock in air : 
 
 Timber ---------- 1,263.6 ton?. 
 
 Copper 16.87 " 
 
 Iron 32.53 « 
 
 Steam engine and supose - - - - - - -10 
 
 Total dry dock - - - - - - - - - 1,323 tons. 
 
 Weight of a ship of the line - - 5,500 
 
 6,823 tons. 
 
 Loss in weight of such parts of the dry dock whieh are constantly immersed - 1,210 
 
 5,613 tons,. 
 
 Rapacity of dry dock - - - - ' - - - 7,117 " 
 
 Surplus power 1,504 tons. 
 
 PETER VON SCHMIDT 
 
 New York, October 6, 1842. 
 
 I. 
 
 Letter from Mr. TV, A. Cox, engineer, relative to the construction and 
 
 use of Schull 6c Martin's dock. 
 
 New York, October 5, 1842, 
 
 Gentlemen : At the interview afforded me this morning to explain, 
 the floating dry dock of Messrs. Schull & Martin, you were pleased to say 
 that any communication which we might desire to make would be received 
 by you, and laid before the Department. I beg leave, therefore, to offer 
 the following brief statement of the dimensions, properties, &c. of a dock 
 upon this plan, suitable for the use of Government, and divested of the 
 railway, cradle, and other parts connected with it, for the purpose of taking 
 the vessel on land : 
 
 1. A dock capacious enough to take up a Government steam ship will 
 be— 
 
 Length 226 feet 6 inches, or 13 floats each, (with its truss framing,) being 
 17 feet 3 inches, and one additional truss at end ; say 17 feet 3 inches X 
 -|- 2 feet 3 inches z= 226 feet 6 inches. Width in the clear, 68 feet. 
 
 Depth from bottom of truss frame to top of keel blocks, 19 feet 6 inches,. 
 
 2. The external dimensions of the dock will be — 
 
46 
 
 Doc. No. 27. 
 
 Whole length required for shafting and machinery, 231 feet 6 inches; 
 whole width occupied by floats and framing, 93 feet ; say 68 feet for width 
 in the clear +12 feet 6 inches on either side for upright posts and ma- 
 chinery, = 93 feet. 
 
 Whole depth, 48 feet; say depth of tanks, &c., as before, 19 feet 6 inches, 
 -|- draught of water of the North Carolina, 25 feet, -|- 2 feet for rise of 
 dock above water, + 1 foot 6 inches additional height of piers for spring 
 tides, zz: 48 feet. 
 
 Noie. — Any extent of solid piers beyond the dimensions here given will 
 be needed only for strength, and may be occupied for any other purposes 
 than those of the dock. 
 
 3. The lifting power will be 5,200 tons; say 13 floats or tanks, each 
 lifting 400 tons, z= 5,200 tons. Subsidiary to this, the dock possesses an 
 almost unlimited lifting power, by means of the racks and pinions against 
 the upright posts — a power which we can render available and safe by 
 proper transverse trussing, and pauls and racks, upon the upright framing. 
 
 4. The number of hands required to work the dock will be — 
 
 1 engineer, 
 
 1 fireman, 
 
 2 extra hands, — 4 in all. 
 
 5. The quantity of air in each tank, and consequently its buoyant power, 
 is indicated in every stage of lifting a vessel by a rod rising from the tank, 
 with an index upon it, and a graduated scale upon the frame work of the 
 dock. The line of the ship's keel is ascertained by a system of levers with 
 indices and graduated scales, before any attempt is made to lift her. The 
 ship is centred by the keel, instead of shores above the water line. 
 
 The keel blocks are so constructed that they can be made to conform to 
 the line of the keel, in the event of its having received any injury, or if 
 the vessel is hogged or broken-backed. The upward pressure of the tanks 
 does not therefore tend to strain the vessel in any part. The machinery 
 which works the pumps is arranged with a view to produce the least pos- 
 sible strain upon the frame work of the dock. 
 
 In conclusion, 1 would add, that every accident which experience has 
 shown floating dry docks to be liable to has been provided against in this 
 one, as far as our knowledge of materials and the best mode of employing 
 them has permitted. The advantage of placing a dock possessing the 
 least possible mobility in such an exposed situation as the navy yard at 
 Brooklyn does not need to be expatiated upon. 
 
 A specification of the particular mode of building the dock, the mate- 
 rials to be employed, and an estimate of its cost, will be forwarded to the 
 Department at the earliest possible moment. Lest any erroneous impres- 
 sion with regard to the cost of the dock should be created b}'- the estimate I 
 named this morning, I would remark that that estimate related to a dock 
 (not coppered) sufficient only to raise a merchantman of 1,000 tons burden. 
 I am, gentlemen, very respectfully, yours, &c. 
 
 W, A. COX, Engineer. 
 
Doc. No. 27, 
 
 47 
 
 Mr. John Thomases letter, relative to the draus;ht of water required on 
 his plan, in order to take up a ship of the line, and on the effect of 
 docking the Pennsylvania. 
 
 City of New York, October 1, 1842. 
 
 Sir : The following are a few remarks, relative lo floating and stone wall 
 docks, which I shall feel greatly obliged if you will lay before the board 
 of commissioners having this subject under consideration. 
 
 I would first remark that, if the Pennsylvania was taken on my floating 
 dock, with all her guns, men, and stores, for six months, her weight, 4,000 
 tons, and her draught of water, 25 feet, to give my dock sufficient capacity, 
 I should have to increase my depth from six to nine feet ; this would give 
 me eight feet of lifting power. I should then have, on seven sections, 
 4,375 tons, added to that 300 tons, the lifting power of my floating wharf, 
 which would make, in all, 4,675 tons ; I should require 34 feet of water^ 
 At slack water, by the aid of a steamer, my dock could be placed and an- 
 chored where 34 feet of water is to be found. I could then take the 
 Pennsylvania on. I would place three wale shores on each section, and 
 back the main 'cleats over the heads of said shores with two smaller 
 cleats. 1 would secure the floor heads with ten bulge blocks on each side. 
 From this it may be seen that she would be supported by 34 keel blocks^ 
 20 bulge blocks, and 42 wale shores, making in all 97 points of bearing. 
 Thus the ship would be completely cradled, as soon as the water had left 
 her load-water line one inch. At the slack water the next tide, with the 
 aid of said steamer, I would take her alongside of the yard in eight feet of 
 water, and the ship secured beyond ihe possibility of straining. 
 
 I will now show what can be done in the stone wall dock at Gosport,. 
 Virginia. There are 26 feet of water on the gate sill of this dry dock ; 
 if it should be found that 22 feet of water is the depth ou the sill of the 
 gate, then my dock at 6 feet will be the same capacity as the Gosport dock, 
 because each will require to have three feet added to its depth. Sup- 
 posing the dock to have 25 feet of water, let us see what is to be done 
 with her when placed in the dock. I suppose the Pennsylvania to be as 
 strong a ship as any ui the world, and that her keel has an upward curve, 
 or aged, not more than four or five inches; this is less than any long ship 
 I have ever known. I suppose the ship placed on straight blocks against 
 her wales, w hich is all that is usual, until the water is drawn from the 
 dock ; then bulge shores are placed at the shore heads, and at various other 
 parts, as the superintendent may think proper. It is impossible to place 
 bulge shores, or vertical wale shores, until the ship's keel is firmly fixed 
 on the blocks, so that the whole weight of the ship, and all that is in her, 
 must rest on the keel. The weight of the projecting sides would rest 
 on the floor timbers, and, their only bearing being on the keel, must strain 
 them exceedingly. The Pennsylvania is yet perfectly sound, and might 
 bear the strain ; but, if attempted in ten years' time, it is not improbable 
 but that her floors would break in the middle, and her bottom fall out in 
 the dock. If my opinion was asked what I thought should be done with 
 said ship if she should return into port in a very leaky state, I would 
 lecommend that the ship be run on the mud, then dismantled, and every 
 thing taken out of her, and then put in the dry dock. 
 
48 
 
 Doc. No. 27. 
 
 From the remarks I have made, I think it may be seen that, if ever the 
 experiment is made, the ship will not be strained on the floating dock, and 
 niuch strained on the stone dock. 
 
 I remain, sir, with srreat respect, your most obedient servant, 
 
 JOHN THOMAS. 
 
 Captain Kennon, U. S. Navy. 
 
 L. 
 
 Notes by Captain M. C. Perry, relative to the depth of water at the 
 
 Brooklyn navy yard. 
 
 Width of channel, which may embrace a depth of 26 feet when exca- 
 vated, say 200 feet ; 80 feet of this width has been excavated ; the remain- 
 ing space may vary in depth at half tides, say from 17 to 22 feet. 
 
 The natural channel, before the excavations commenced this spring, 
 varied in depth from 17 to 26 feet. There was not width to wind a Une-of- 
 battle ship. 
 
 M. 
 
 Statement presented by Mr. Dakin of interest lost in building an exca- 
 vated stone dry dock before it can be finished ready for use. 
 
 Suppose the cost to be only $1,200,000, though Mr. Rhodes is of opinion 
 that at Brooklyn the cost will be considerably more. The shortest time 
 within which any one supposes it could be tinished is 6 years, which makes 
 an expenditure of $200,000 a year. The Government now pays 7 per cent, 
 for money, and must probably do so for some years. 
 At the end of the first year after the expenditure of $200,000, say 
 one-half of it expended the first 6 months, the interest at 7 per 
 cent., 1 year, on $200,000, and six months on $100,000, is - $17,500 
 At the end of second year interest on $400,000 one year, and 
 
 $100,000 6 months, is - - - - - - 31,500 
 
 Third year $600,000, and $100,000 6 months, is - - - 45,500 
 
 Fourth year $800,000, and $1 00,000 6 months, is - - - 59,500 
 
 Fifth year $1,000,000, and $1 00,000 6 months, is - - - 73,500 
 
 Sixth year ^ 1 ,200,000, and $ 1 00,000 6 months, is - - - 87,500 
 
 Total - 315,000 
 
 Add to this the extra expenses the Government would be exposed to in 
 various ways, in consequence of having no means of raising vessels at 
 Brooklyn during this six years, and it will probably be sufficient to con- 
 struct a floating dock for the Pennsylvania, with full armament, leaving 
 the convenience of having the dry dock within six or eight months, instead 
 of waiting six or eight years — a clear saving over and above all the rest 
 of the gain of building the floating dock out of the losses attending on build- 
 
Doc. No. 2T* 
 
 49 
 
 mg the stone dock, exclusive of its gross expense. It is also to be observed 
 that the interest on the cost of a stone dock, which is say ^70,000 per 
 annum, will build a floating dock of the largest size every six years or 
 thereabouts. 
 
 The above estimates do not take into consideration the superior facilities 
 afforded to the workmen an the floating dock, which enable them to do 
 the work 15 to 20 per cent, cheaper than on the stone dock, nor the great 
 saving of old copper materials lost on other docks, nor the great advan- 
 tage, afl*orded only by the sectional dock, of being enabled to raise two or 
 more vessels at a time, and. doing simultaneously twice, or more, the actual 
 work that can be done by any other dock. 
 
 - It is worthy of consideration, also, that it is very doubtful whether the 
 two vessels now laid up at the Brooklyn yard can wait for the completion 
 of a stone dock, and would not, in fact, be ruined before that time. 
 
 N. 
 
 Mr. John S. GilberV,^ notes on t/ie weight and. displacement of his dock 
 
 when afloat. 
 
 Weight of materials, 
 . Cubic foot. 
 
 Round stone . - - - , lbs. 160 
 
 Sea water - 64 
 
 Oak timber - - - - , - 60 
 
 Price ' - - - - - 30 
 
 Iron 486 
 Displacement of the dock, 615 tons to a perpendicular foot. 
 
 120,000 cubic feet of timber to build the dock. This timber is ma^e as 
 
 heavy as water by adding ballast; each cubic foot of timber is made to 
 weigh 64 pounds ; weight of dock, 3,840 tons when ballasted. 
 
 Washington, October 27, 1842, 
 
 Sir : The undersigned have, agreeably to your request of yesterday, exam- 
 ined the model of a floating dry dock, presented to the consideration of the 
 Department by Messrs. Starkweather & Tallmadge, accompanied by Mr. Cox, 
 the gentleman with whom we had some communication on the same subject 
 in rsew York. For our remarks on the principles of Messrs. Schull & Martin's 
 dock, which is in fact the one now under consideration, we beg leave to 
 refer you to the statement contained in the sixth article of our report, under 
 date of the Sth instant. The objections to this form of dock, on account of the 
 great depth of water required, the necessity of deeply founded and per- 
 manent stone piefs, to be laid in cement, and consequently the probable 
 demand of coff"er dams to secure their foundations, and of the gates or 
 aprons to exclude the influx of mud, must be regarded by us as still exist- 
 ing in full force, especially since the estimate, mentioned by the gentlemen 
 tfiemselves (^500,000*) as the cost of a dock to receive ships of the line. 
 
 * A subsequent offer, in writing, was made at $450,000. — S. H. 
 4 
 
50 
 
 Doc. No. 27. 
 
 is, if we are not misinformed, more than half, if not more than two-thirds, 
 the cost of the permanent waJled dock at Charlestown navy yard. One ob- 
 jection mentioned by ns in the report before referred to, namely, that 
 arising from the employment of machinery to elevate and depress the 
 dock, and the inconvenience and derangement likely to arise from the 
 great strain to which the rise and fall of the tides would subject such ma- 
 chinery, has been sought to be obviated by the engineer, by allowing the 
 machinery to play in obedience to the. rise and fall of water. If this 
 principle be applied, it will require additional parts of machinery to adapt 
 it to this purpose ; it will require more buoyant power in the tanks to set 
 the machinery in motion on a rising tide, and to lift the ship, than would 
 be necessary for the latter purpose only, and on a falling tide a part of the 
 weight of the vessel would be employed in overcoming the friction of the 
 train of wheels, pinions, &c., and consequently she would not sink so low 
 as the tide fell, nor rise as high as the tide rose, by the difference due to 
 the friction in both cases. The water must consequently be nearer the 
 keel in one case than the other ; and whether this would occasion serious 
 inconvenience or not must depend on the accuracy with which the machi- 
 nery worked. That a train of shafts, wheels, pinions, and racks six hun- 
 dred and thirty feet in length, may be made to act in unison, is unques- 
 tionably true, but that it Would have the simplicity, ease of repair, and 
 general permanency of the machinery in an excavated and walled dock, 
 or even of some forms of floating dock, we are by no means prepared to 
 admit. The arguments which were used in the interview which we had 
 with the proprietors of this dock, to convince us of the want of title to the 
 plans used by some of the parties in New York, we do not conceive it 
 necessary for us to dwell upon, as the question of ownership obviously 
 belongs to other tribunals. 
 
 With the above views, we do not feel authorized to recommend this 
 plan for the adoption of the Department. 
 All which is respectfully submitted by 
 
 Your obedient servants, 
 
 BEVERLY KENNON, 
 
 Captain U. S. Navy. 
 SAMUEL HUMPHREYS, 
 WALTER R. JOHNSON. 
 
 Hon. A. P. Upshur. 
 
 New Xork, October 28, 1842. 
 
 Dear Sir : I wish the following additions and modifications to be made 
 to the proposals heretofore submitted by me for building a sectional float- 
 ing dry dock for the United States navy, viz : 
 
 1st. I propose to build each section according to thfe plan and-drawings 
 submitted a few days since to the Department, both as to the general di- 
 mensions and as to the size of the particular timbers, and all the details of 
 the structure to be satisfactory in every respect. 
 
 2d. I propose to cover all parts of the timbers, tanks, and floats, exposed 
 to the action of salt water, with zinc of satisfactory thickness. 
 
 3d. In my proposition already submitted, I did not contemplate an ex- 
 tension of the structure beyond 4,500 tons ; but, having learned that the 
 
Doc. No. 27. 
 
 51 
 
 Pennsylvania, fully armed and loaded, weighs 5,200 tons, and that it may 
 be deemed expedient to enlarge the dock to that capacity, which could be 
 done without much additional expense, as it is not so great an extension 
 as to require an additional section, I propose to furnish the dock complete, 
 including zinc sheathing, with a dear lifting power of 5,300 tons, applica- 
 ble to raising vessels, for the sum of ^400,000 ; or to furnish the same, 
 complete as aforesaid, with a clear lifting power of 2,650 tons, sufficient 
 to raise an eighty-gun ship, unloaded and unarmed, for ^200,000. 
 
 4th. I propose to keep the structure perpetually in repair, if desired, 
 for the use of it, when not actually wanted for Government vessels, hold- 
 ing it at all times ready to be surrendered to the Government on a few 
 hours' notice. 
 
 5th. I propose, with the money already put at your disposal by Cor;- 
 gress for this purpose, to provide means^ within six months, by building 
 three sections, to act in conjunction with our establishment, to raise the 
 two ships of the line, Franklin and Washington, now lying in the water 
 at. Brooklyn, which, if neglected a year or two more, and long before a 
 stone dock could be built, will be utterly ruined and beyond the reach of 
 repair, but, if raised and taken care of, now are worth to the Government 
 at least four hundred thousand dollars. 
 
 Very respectfully, yours, 
 
 S. D. DAKIN, President, fyc, 
 
 Hon. A. P. Upshur, 
 
 Secretary of the Navy. 
 
 Washington City, October 29, 1842. 
 
 Gentlemen: The undersigned, in behalf of themselves and associates, 
 propose to construct a floating dry dock for the Government, agreeably to 
 the annexed specifications and drawings, herewith delivered, for four hun- 
 dred and fifty thousand dollars. 
 
 In point of durability, this dock is not essentially, if at all, inferior to the 
 wall dock, is as easily repaired, can be worked more expeditiously and at 
 much less expense, and, having full confidence in its stability, we are willing 
 to guarantee it to the Government, in this particular, by the most satisfac- 
 tory security. 
 
 Shall the Government wish a dock of smaller dimensions for sloops of 
 war, and we will construct the same at a price corresponding with its ca- 
 pacity ; and, in the event of our undertaking a dock, we shall be pleased 
 to prosecute the same under the supervision of a competent officer, to be 
 assigned by the Government. 
 
 Respectfully, yours, &c. 
 
 HENRY F. TALLMADGE, 
 S. STARKWEATHER, 
 WM. A. COX. 
 
 Messrs, Kennon, J 
 
 Humphreys, and > Commusioners^ Spc. 
 Johnson, 3 
 
52 
 
 Doc. No. 27 
 
 Philadelphia, October 11, 1842. 
 
 Sir : In drawing up the report of the commissioners on the subject of 
 floating docks in New York, there was felt the want of an opportunity to 
 consult certain reports on the same subject, made as long ago as 1S26. 
 
 Having, since my return to this city, referred to the proper publications, 
 1 have made the accompanying copy of an able report to the Franklin In- 
 stitute, which, as it sustains many of the views of the commissioners, and 
 as it emanated from gentlemen amply qualified to understand and explain 
 the subject, seems to me entitled to a place among the documents now in 
 the Department on the subject of floating docks. 
 
 I have subjoined references to other published reports relative to floating 
 docks and marine railways. 
 
 I remain, very respectfully, your obedient servant, 
 
 WALTER R, JOHNSON. 
 
 Hon. A. P, Upshur, 
 
 Secretary of the Navy. 
 
 [From the Franklin Journal, vol. page 3, January, 1827.1 
 
 Beport of a select committee^ appointed by the Franklin Institute, on a 
 dry dock projected by Commodore James Barron^ and also one by 
 Captain Thomas Caldwell. 
 
 The committee appointed by the Frankhn Institute, of the State of Penn- 
 sylvania, to examine the plan of a dry dock submitted for examination by 
 Commodore James Barron, of the United States navy, and of another dry 
 dock submitted by Captain Thomas Caldwell, report ; 
 
 That the immense importance of dry docks to the people of this great 
 commercial nation has induced the committee to delay the presentation of 
 their report, in order that a thorough investigation of the merits "and de- 
 fects of the various plans now in operation, and those now proposed to 
 the Institute, might be effected. 
 
 The United States present the only instance existing of a great com- 
 mercial people destitute of dry docks for building, coppering, examining, 
 cleaning, and repairing their national and commercial marine. 
 
 The large ships of war of the nation are at present suffered to decay 
 when serious repairs are requisite, which might easily be performed if dry 
 docks were in existence in the Union. 
 
 The danger and expense from this neglect require immediate attention, 
 and the national welfare demands the establishment of docks without fur- 
 ther delay. The system adopted by our merchants, in heaving down ves- 
 sels of large dimensions, when repairs are required, is at once expensive, 
 dangerous, and. incomplete ; expensive, for it requires the removal of their 
 cargoes, and of many articles from the ships, to qualify them to sustain 
 this severe and straining operation, whilst much time is lost and much la- 
 bor expended in the processes subsequent to the heaving down, as well as 
 in the preliminary operation ; dangerous, as the violent and unavoidable 
 straining of the timbers, bolts, copper, &c., must weaken and injure the 
 vessel ; incomplete, as thorough repairs cannot, in many cases, be per- 
 formed, and as the injury done cannot always be completely ascertained 
 
Doc. No. 27. 53 
 
 perhaps not until danger in a storm at sea reveals the extent of (he evil, 
 when discovery is almost unavailing, from the impossibility of then repair- 
 ing the damage. For all these reasons, your committee most strongly con- 
 demn this process. 
 
 Our merchants, aware of these facts, are sometimes compelled to send 
 their vessels to the dry docks of Europe, when coppering or serious re- 
 pairs are requisite. The necessity of employing the ship builders of for- 
 eign and sometimes hostile nations, (with whom intercourse may be in- 
 terrupted by national disputes,) and particularly our thus depriving of em- 
 ployment our own ingenious and skilful ship builders and mechanics, who 
 are now frequently unemployed for a portion of every season, and whose 
 labor is therefore lost to the nation, all dictate the necessity of a change ; 
 for it cannot be doubted that, if dry docks existed in the ports of our coun= 
 try, all the operations of building and repairing vessels could be performed 
 here with moi^e economy and with greater despatch, with equal excel- 
 lence and with far greater convenience, than at present. 
 
 Many of these advantages will, in a comparative degree, be experienced 
 by such ports in our country as may adopt docks over such as are destitute 
 of these highly important structures. 
 
 The committee consider it foreign to the object of their appointment to 
 express any opinion in relation to the railway docks which have been re- 
 cently constructed in the United States. 
 
 Previously to commencing our examination of the comparati\^e advan- 
 tages of the plans now submitted to us, we will describe those which have 
 been heretofore in use. 
 
 The dry docks employed in Europe resemble, in their structure, the 
 larger class of locks which are used on canals; but they are usually far 
 more expensive to construct, in proportion to their relative magnitude. 
 Necessity frequently requires their location in a marshy or loose soil ; the 
 dock pit must be excavated to a great depth, frequently much below the 
 surface of the adjoining harbor ; much caution and labor are requisite to 
 exclude or remove the water from the excavation. To prevent accidents 
 from the adjacent earth slipping in, and thereby injuring or retarding the 
 works, it is frequently necessary to allow a considerable slope to the sides 
 of the dock pits ; consequently, much labor is expended in the excavation. 
 Many piles, driven to a considerable depth, are required, the masonry de- 
 mands much labor to ensure durability, and hydraulic cement is indispen- 
 sable. Stone dry docks are consequently very expensive structures; 
 §75,000 or ^80,000 being the least estimate which can be relied on for the 
 cost of a dock,* including the appurtenances, calculated for vessels of 300 
 or 400 tons, and a larger sum for ships of greater magnitude. 
 
 A dock of this description could not be completed in less than one, and 
 would, probably, require two years. The interest of the capital employed 
 in constructing the work (which is unproductive during this period) will 
 of course add to the above expense, a;nd, should no delay take place in 
 commencing the docks, our shipping must inevitably suffer during the 
 above period of time. 
 
 . When stone docks are well constructed, few repairs are required ; if, on 
 the contrary, the plan or the structure be defective, much time, much de- 
 
 * The above estimate is calculated for the vicinity of Philadelphia ; land, workshops, sheds, 
 and other bi^ildings. are not included in it. 
 
54 
 
 Doc. No. 27 
 
 lay, and great expenditure of money, may be required to maintain them 
 in repair or to remedy their defects. 
 
 When the height of the rise and fall of the tides is greater than the 
 draught of the shipping, for which the docks are constructed, steam or 
 other engines, applicable to pumps, are not required to remove the water ; 
 but, with the exception of the extreme northeastern coast of the United 
 States, the maritime districts of our country will require docks in which 
 pumps will be indispensable. The engine employed must be sufficiently 
 powerful to perform this operation with expedition. 
 
 In the plan submitted by Captain Thomas Caldwell, which is accompa- 
 nied by a neady constructed model, it is proposed to dispense with the use 
 of pumps, whenever a supply of water of sufficient elevation can be ob- 
 tained. He proposes to construct a dock of about twice the usual length, 
 to be divided into two compartments by gates situated near the centre of 
 the structure ; an additional pair of gates are placed at the extremity y 
 opening a communication with the harbor. The vessel enters this first 
 compartment; the external gates are then closed, and the internal opened. 
 The bottom of the second compartment is above the level of water in 
 the first or outer compartment, and is, consequently, at this period dry. 
 The water is now permitted to flow from the elevated reservoir, through a 
 pipe, into the docks ; when, by this means, the surface is sufficiently eleva- 
 ted, the vessel is hauled into the second cpmpartment, which is constructed 
 in all respects similar to a dry dock ; the central gates are then closed and 
 secured, and the water is discharged into the adjacent harbor. This plan 
 may be adopted in any situation, and is entirely independent of the tide, 
 although this may occasionally be of some assistance. 
 
 All that is proposed in this place is to save the difference in the expense 
 of erecting steam engines, or other powers applicable to pumps, together 
 with the cost of maintaining them in operation, compared with the 
 cost of pipes and of obtaining a supply of water. In the cost of these 
 items some saving may, perhaps, be effected ; .but all plans of this descrip- 
 tion, however simple they may appear, must be far more expensive than 
 any which are now in use. The money which would be required to con- 
 struct the external dock, or rather lock, of which it is an exact resemblance, 
 would be sufficient to construct one and perhaps two dry docks on the 
 common plan ; whilst the interior dock will require the expenditure of the 
 sum usually required in addition to the former: Steam engines or other 
 power could be maintained for a far less sum than the interest of the 
 extra capital which we have mentioned above. The committee, therefore, 
 cannot recommend this plan for adoption. 
 
 This method is by no means novel ; it has been frequently described, but 
 we believe never adopted. 
 
 In all docks from which it is necessary to remove the water, either by 
 means of pumps or the action of the tide, some delay always occurs. It is 
 sometimes important that ships should be enabled to proceed to sea with 
 all possible expedition. This remark is applicable to our mercantile, but 
 more especially to our national marine. The success of a naval expedition 
 may depend on the promptness with which it can be equipped for sea. A 
 single defective vessel may detain a whole squadron until the defect can be 
 remedied. 
 
 The time lost in waiting for a single tide may be of consequence ; hence 
 docks from which the water is removed by powerful engines may, in some 
 
Doe. Mo. 27 
 
 55 
 
 few cases, have advantages over those which depend on the tide for this 
 purpose ; the latter, however, are certainly more economical, both in their 
 use and construction. The application of these remarks will be considered 
 when we describe the plan of Commodore Barron. 
 
 The walls of dry docks necessarily exclude a considerable portion of the 
 light; consequently the workmen are unable to perform their task early in 
 the morning or late in the evening. Artificial illumination has sometimes 
 been partially resorted to for the purpose of lessening the inconvenience. 
 From the cause above mentioned, some inconvenience is experienced from 
 the want of ventilation ; hence the vessels in the dock cannot, when requi- 
 site, be expeditiously dried, unless by the aid of fire, the employment of 
 which for this purpose has been productive of numerous accidents. An 
 addition^ evil resulting from this dampness and want of ventilation may 
 be observed in the diseases contracted by the workmen employed in such 
 docks. - 
 
 The hulks of old ships are sometimes employed in Europe as substitutes 
 for stone dry docks ; they are drawn ashore between high and low water 
 mark, and carefully secured ; the stern is cut off and replaced by a pair 
 of gales ; the hold is partly filled with ballast, to reduce the buoyancy of 
 the ship ; the vessels enter at high tide, and are knmediatfely secured by 
 shores, &c. The water is permitted to escape during the subsiding of the 
 tide, and afterwards kept excluded from the interior of the dock during the 
 time of repairing the vessel. 
 
 This plan may be sometimes successfully resorted to for small vessels, in 
 cases of emergency, but it is inapplicable to ships of great magnitude. 
 In addition to this objection, an enormous quantity of ballast is required ; 
 and, notwithstanding all the precautions which may be taken, accidents will 
 sometimes occur from the employment of this insecure apparatus. 
 
 In the State of Maine, a plan similar to this has been attempted, but a 
 vessel, in the form of a camel or rectangular trunk, has been substituted for 
 the hulk previously mentioned. The least inequality on the surface of the 
 soil on which it rests will endanger its stabihty by causing it to warp, and 
 of course jeopardizing the safety of the vessel contained in it. 
 
 In addition to this, it can only be employed where the tide rises and falls 
 many feet, unless pumps be used. 
 
 We now proceed to describe the ingenious plan submitted to us by Com- 
 modore James Barron, of the United States navy. It presents the appear- 
 ance of a large scow, constructed in the strongest manner. The great sim- 
 plicity of the features of this plan will render it perfectly intelligible by a 
 mere inspection of the subjoined drawing, which represents a section of the 
 dry dock : 
 
 [Here follows a diagram.] 
 
 D D D D, the dock k k, knees at the angle, bolted firmly to the horizontal 
 and upright timbers DDDD;ccccc, horizontal or inclined slips of ceil- 
 ing, running fore and aft, into which the timbers D D D D are inserted ; 
 the external planking of the dock is to be well caulked ; T T T T are air- 
 tight trunks, to preserve the buoyancy of the dock when filled with water; 
 V, the vessel in the dry dock ; S S, two of the wale shores supporting the 
 ship ; p p., horizontal shores ; B B, blocks under the keel. 
 
 Port holes, which may be rendered water-tight, similar to those in ships 
 of war, are placed at suitable intervals in the sides of the dock ; these will 
 
56 Doc, No, 27, 
 
 permit the access of light and air — a great advantage, which is not possess- 
 ed by the docks now in use. These port holes also offer facihties for the in- 
 troduction of timber, &c. 
 
 At the extremity of the dock, facing the harbor, the gate is placed ; this 
 may be of the usual form, or in detached parts, or the floating gate may 
 be employed. The latter has been for a long time in successful operation 
 in Europe. 
 
 If this dock be employed in salt water, where the worms are destructive 
 to timber, it will be necessary to protect it with copper, &c. This will be 
 requisite only on the bottom and sides ; the latter will require coppering 
 only as high as the floating line of the dock containing the vessel when the 
 former contains no water. The same remark is applicable to the copper 
 bolts. As the dock is exposed to little friction, the thinnest sheets of copper 
 may be employed.* 
 
 We now proceed to describe the method of using this structure. When 
 the gates are open the dock is full of water, and sinks to a depth to allow 
 vessels to enter therein, and of course to displace their weight of water 
 from the dock when the gates are closed and secured. The vessel is then 
 shored, &c., in the usual manner employed in dry docks. The water must 
 be removed either by common pumps, by Archimedes screws, or by a 
 pump which forces out the water through an aperture in the bottom. This 
 latter method is decidedly the best, for by means of it the water can be re- 
 moved in one-fourth of the time which would be required by the first plan= 
 
 For the purpose of explaining this subject, we will describe the process 
 of pumping out the water from a common dry dock, and the power which 
 is requisite for this purpose, compared with the floating dock of Comrno- 
 doiH3 Barron. 
 
 [Here follows diagram.] 
 
 In figure 2, D represents a dry dock of the usual form, S the ship, H A 
 the level of the water in the harbor and dock, the line A B the depth of 
 the dock — for instance, 20 feet. 
 
 At the commencement of the operation of pumping, as the level of the 
 water in the dock and harbor is the same, no power is requisite to remove 
 the water from the dock, (if the friction of the pumps be not considered ;) 
 as the pumping proceeds, the surface of the water in the dock sinks below 
 the level H A of the water in the harbor ; of course power is now required 
 to elevate the water. The difference between the heights of these two sur= 
 faces continually increases until the last portion of the water in the bottom 
 of the dock is to be removed, when the elevation to which the water must 
 be raised is the greatest, viz : from B to A, (20 feet ;) of course the great- 
 est power is required at this period of the operation. Therefore, if every 
 foot in depth of the dry dock contain equal quantities of wafer,t the aver- 
 age power required during the whole of the operation must be sufficient 
 to elevate a quantity of water equal to the cubic contents of the dry dock, 
 to a height equal to one-half of the depth A B of the dock D, viz : to the 
 
 * If the experiments of Sir Humphrey Davy be conclusive, the copper may be perfiectly pro- 
 tected from corrosion in salt wrater by employing iron guards. The adhesion of barnacles, &c., 
 which may be the result of preventing the oxidation of the copper, will be no impediment what- 
 evej to the operations of the floating dry dock. 
 
 -j- In practice, the lower portion of the dock will, from the form of the ship, contain more water 
 lhan the upper portion, and of course require more power and more pumping to retnove it. 
 
Doc. No. 27. 
 
 57 
 
 half of 20 feet, equal 10 feet, equal x A. This supposes that the level H A 
 of the water in the harbor remains constant. In the floating dock of Com- 
 modore Barron, much less power is required to remove the water. 
 
 [Here follows a diagram.] 
 
 Let D D D D, figure 3, represent the floating dock, containing the ship 
 S ; H A the surface of the water in the harbor, which would coincide with 
 the surface in the dock, supposing it to be sunk to the dotted line, which is 
 its situation when full of water ; this depth we suppose to be 20 feet, or 
 equal to A B, figure 2. At the commencement of the operation of pumping 
 the water from the floating dock, it resembles the common dock in not re- 
 quiring any power to exhaust it ; but, as the pumping proceeds, the dock 
 becomes lighter, and of course the bottom does not remain in the same 
 relative position to the surface of the water in the harbor, but rises in pro- 
 portion to its buoyancy. 
 
 The above figure 3 represents this dock as having risen in consequence 
 of the removal of the water H A, being the surface of that in the harbor j 
 it is now immersed to the depth of A B only, which, in a dock of the mag- 
 nitude hereafter to be mentioned, will be about 5 feet ;* consequently, as 
 the water is forced out through an aperture in the bottom, the greatest 
 resistance to be overcome is equal only to the pressure of a column of wa- 
 ter equal in height to the line A B, (5 feet ;) half of this, or A a7=2i feet, 
 will be the average resistance during the whole operation. Therefore, the 
 power required to remove the water from the floating dock, by a forcing 
 pump, will be to the power required to remove the water from a common 
 dry dock, on the usual plan, as 2\ to 10, or as 1 to 4, viz : as A a:, figure 3= 
 2^ feet, is to A a:, figure 2=10 feet. If, however, lifting or forcing pumps 
 be employed to pump the water up, and discharge it over the sides, the 
 same power would be required both for the fixed and for the floating 
 dock ; of course the forcing pump previously mentioned will be adopted 
 for the floating dock. 
 
 The dock of Commodore Barron is to be moored in a slip between two 
 wharves or breakwaters, which will flank and protect it from injury ; a 
 raft or floating breakwater moored in the harbor in front of the dock gate 
 will preserve it from damage by storms, &c. 
 
 The repairs of this dock can be effected with despatch and economy j if 
 the bottom requires inspection, the dock can be hauled up on a common 
 building slip, and examined. 
 
 No danger can be apprehended from the bottom or other parts of the 
 dock warping ; for this can be prevented by proper care in the construction. 
 
 Your committee have now fully and decidedly stated their opinion of 
 the ingenuity, economy, the safety, and the perfect practicability of the 
 valuable plan invented by Commodore Barron ; but they would fail in 
 gratifying their own feelings, as well as in the performance of the duty 
 which they owe to the public, if they concluded this report without ear- 
 nestly recommending this scheme to our mercantile community, for their 
 immediate adoption. 
 
 The most prudent and cautious may be informed that the correctness of 
 
 * As it will not be necessary to remove the water from the space occupied by the ballast, (repre- 
 sented by the shaded compartment in the lower part of the figure,) the additional depth to which 
 the dock will sink will not affect the result of the calculation we have given. 
 5 
 
58 
 
 Doe. 27. 
 
 the principles on which this dry dock is founded are so completely demon- 
 strable, that success cannot fail to crown the efforts of those whose enter- 
 prise may induce them to attempt the estabUshment of a dock on this plan 
 An able and faithful superintendent or engineer must be employed, as, 
 without such supervisiori, every similar scheme will prove abortive. 
 
 The experiment may be tried on a small scale, by those whose caution 
 mduces them to dread the failure which may, by possibility, result from 
 any plan which has not been frequently and successfully reduced to prac- 
 tice. In the event of a trial, only ^4,400 need be expended on a floating 
 dry dock calculated for the reception of vessels of 300 tons. Wharves and 
 floating rafts, which will form a suflicient temporary protection, can be 
 easily procured. Common pumps, worked by men or horses, will be suf- 
 ficient to remove the water.* 
 
 If the experiment be successful, the most ample remuneration must m- 
 evitably be the reward of the proprietors ; if the plan proposed be unsuc- 
 cessful, the materials of which the dock will be constructed can be sold for 
 1,400, and a loss of ^3,000 only can possibly occur. The lock can be 
 finished in the short space of two months. 
 
 If the experiment on this scale be successful, (and of this the committee 
 do not entertain the smallest doubt,) the most timid will not hesitate to try 
 the plan on a larger scale, and with the additions thereto which conven- 
 ience may require. 
 
 All which is respectlxiUv submitted. 
 
 S. HUMPHREYS, b\ 6'. Naval Constructor. 
 CHARLES STEWART, U. S, Navy. 
 A. J. DALLAS, V, S, Navy. 
 HARTMAN BACHE, Top. Engineer. 
 JOHN RANDEL, Jun., Civil Engineer. 
 GEO. W\ SMITPL 
 t JOHN WILSON, Civil Eng.. of SouthCarolinn. 
 
 In the same volume of the Franklin Journal which contains the report 
 on Barron's and Caldwell's docks (viz : vol. 3, p. 73, Feb. 1827) is a des- 
 cription of the American marine railway^ as constructed at New York 
 by Mr. John Thomas, naval architect, with explanations of its principles^ 
 and manifestations df its safety, for ships of war^ by John L, Sullivan^ 
 civil engineer.^' This report embraces 12 pages of the journal, and is ac- 
 com.panied by two copperplate engravings. The marine railway referred 
 to in the report of the commissioners is believed to be the same as that des = 
 cribed by Mr. Sullivan. 
 
 In the same volume (p. 424) is a report of the Committee of In- 
 
 * The tota\, expense of these items for a permanent establishment will not exceed $6,000, or 
 the total expense for such an establishment will be only $10,400. 
 
 t It may be proper to state, that Mr. Wilson was present at several meetings of the committee, 
 and approved of the notes then taken by the committee. As these required some alteration in 
 their arrangement to render them fit for publication, and as Mr. Wikon was compelled to leave 
 Philadelphia in the interval, it was impossible for him to attach his signature in time ; and it hat 
 therefore been done during his absence. This explanation is due to him and to the public, 
 
Doc. Xo. 27. 53 
 
 veniions of the Franklin Institute on thf^. plan of a floating dry dock, in- 
 vejited by Edtvard Clark, civil engineer. This is accompanied by a 
 copperplate engraving, which shows that INJr. Clark^s is one of the class of 
 tank docks which left the vessel's keel qiiile above the water. It is built 
 between two piers, which have guide timbers up and down to steady the 
 dock as it rises and falls, and to prevent its oversetting in consequence of 
 carrying a heavy weight upon t he top of boxes filled only with air. 
 
 In the same volume, (p. 99,) under the head Committee of Invej'tions, is a 
 *^ report on the radiating railways for the repair of vessels, invented, 
 by Edward Clark, civil engineer. New York," [with a plate.] 
 
Avery Architectural and Fine Arts Library 
 Gift of Seymour B. Durst Old York Library 
 
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