REPORTS GEN. JOHN NEWTON, U.S.A., GEN. Q. A. GILLMORE, U. S. A., WM. E. WORTHEN, Esq., C. E., TO THE COMMISSIONERS OF DOCKS, THE BULKHEAD WALLS CANAL AND KING STS. North River. 1876. Ex ICtbrta SEYMOUR DURST When you leave, please leave this book Because it has been said "Ever thing comes t' him who waits Except a loaned book." Avery Architectural and Fine Arts Library Gift of Seymour B. Durst Old York Library REPORTS OF GEN. JOHN NEWTON, U. S. A, GEN. Q. A. GILLMORE, U. S. A., WM. E. WORTHEN, Esq, C. E, COMMISSIONERS OF DOCKS, THE BULKHEAD WALLS CANAL AND KING STS., North River. 1876. ERRATA. Page ii. Eleventh line from top, for " structure" read "structures." 17. Second " " " " " leveling, of " read " leveling-off." 17. Sixth " 11 " "being" " 11 was." 23. Seventeenth line from top ; omit the word u each." 33. Thirty-third " " " for " field " read " seam. " 44. Twenty-third " " " after "on the other" insert "hand." 44. Twenty-eighth line from top, for " met " read " me ;" and for " me " read 45. Tenth line from top, for " Plate " read " Plate I." 46. Tenth " " " " " ounding" read " sounding." 46. Twenty-eighth line from top ; omit the words " see sketch." 48. Fourth line from bottom, for " horizontal " read " horizontally." 53. Ninth line from top ; omit the words u see sketch." 53. Twelfth" " " " u " " see shaded part of sketch." 53. Third line from bottom ; omit the words, " see shaded area at X." 54. Second" u " for " Plate " read " Plate II." 59. Twenty-second line from top, for " enter " read " enters." Digitized by the Internet Archive in 2013 http://archive.org/details/reportsofgenjohnOOnewy DEPARTMENT OF DOCKS. COMMUNICATION TO THE MAYOR. Department of Docks, } New York, September 22, 1875. f Hon. W. H. Wickham, Mayor : Sir — The undersigned, Commissioners of the Department of Docks, have the honor to transmit herewith report of the Engineer-in-Chief of the Department, in which is detailed the result of examinations made of sections of the sea-wall now nearly completed at Canal Street and King Street, North River. We invite your careful attention to this report, and to the following brief narrative. The original plan for the construction of the sea-wall, devised by General McClellan, the then Engineer-in-Chief, is known as the beton block system, which consists of the formation of massive concrete blocks formed in molds, and manufactured in the open air, in such sizes as the nature of the work demanded. These blocks, when prop- erly hardened, were lowered by the aid of the large floating derrick to a foundation of piles firmly driven, and then sawed off so as to form an even bed. An example of this system of construction is found at the Christopher Street section. In the month of July, 1873, General Charles K. Graham was ap- pointed Engineer-in-Chief of the Department, in place of General McClellan, who had resigned. It appears from the records of the Department, that in the month of October, 1S74, with a view to more economy in the construction of the sea-wall, the Engineer-in-Chief recommended to the Board, as a sub- stitute for beton blocks, that concrete en masse should be formed upon a foundation of piles in a wet caisson, the concrete being lowered to its place within the caisson (by appropriate machinery), in tilting buckets, and then left to harden in a solid mass. The heads of the piles were not cut off after being driven. In the month of November following, our predecessors, by formal 4 resolution, adopted the recommendation of General Graham, and or- dered the work to proceed, which was done, and about 347 feet were constructed. For particulars concerning this system of bulkhead wall construc- tion, see report of General Graham herewith enclosed. The new Board of Commissioners was organized on the 2d day of May last, and, on the 2d of June following, General Graham resigned the office of Engineer-in-Chief, and, as soon as practicable, his succes- sor, George S. Greene, Jr., was appointed to fill the vacancy. The attention of Commissioners being called to possible defects in this method of construction, the subject was referred for investigation to the Executive Committee, who directed the Engineer-in-Chief to make a careful examination of the work, and report the result. The difficulties attending the examination in turbid water, and the results thereof, are explained in the Engineer-in-Chief's report. The examination has proceeded far enough to excite in our minds very grave apprehension as to the safety of that portion of the wall covered by the report. If our apprehension should be well founded, we desire to avail our- selves of such remedy as the combined wisdom of the highest authori- ties may be able to suggest. This is not only due to the great interests of the city, but it seems also just that individuals who may be consid- ered responsible for the work, should have the advantage of the fullest and fairest examination of it, by a body of men of such capacity and character that their decision shall be accepted by all. We have, there- fore, thought it desirable to have an examination of the wall covered by this report made by three engineers of the first eminence, and to invite their suggestions as to the remedy to be applied, if any is thought necessary by them. That we may secure the utmost impartiality in this investigation, we have deemed it proper to request your Honor, as the Chief Magistrate of the city, to name three suitable persons for this purpose. Very respectfully, S. H. WALES, H. F. DIMOCK, JACOB A. WESTERVELT, Commissioners of Docks. REPORT OF THE ENGINEER-IN-CHIEF. Department of Docks, j Office of Engineer-in-Chief, > New York, Sept, 1 6, 1875. ) To Hon. Henry F. Dimock, Chairman Executive Committee : Sir : — Immediately after my appointment to the position I now hold in this Department, I received a communication from the Executive Committee, calling my attention to certain reports received by said Committee in relation to the Canal Street section of the bulkhead-wall, and requesting " that you will make a most thorough investigation and examination as to the* character of the work performed, and the man- ner of constructing the section of wall referred to, and report to them in writing the result, and your opinion in regard to the construction of said wall." In accordance with the above I have made constant examination ot the Canal Street section, and have also examined the King Street sec- tion, which was built upon the same plan and principle, and have de- voted as much time as possible to this subject, consistent with my other duties. The examination of these walls has taken much time, because the greater part of them lies under water, and had to be examined by means of divers in armor ; and although I have not yet been able to make so complete an examination as I wish to, I have ascertained cer- tain facts in regard to them, which I deem it my duty to lay before you at the earliest possible moment. The Cinal Street section embraces 90 feet of wall, completed before my appointment, and in front of which New Pier No. 34 was also built before my arrival on the field, and about 90 feet more in progress ot construction at that time. Upon examining the method of the work I found it necessary to at once make several changes in the details, and although feeling a lack of confidence in the principle of construction, I decided to allow this portion of the wall under construction to be finished, taking care that the method of doing the work and the details should be such as to secure a good result if the principle admitted it. The general plan of construction was as follows : The mud was dredged out on the site of the wall to about twenty feet below mean low water. Round piles were then driven for the wall to rest upon, by means of a follower, to such depth that their heads, or tops, were about fourteen feet below mean low water. A box or wet caisson was then 6 constructed around the round piles, to give shape to the concrete and prevent the cement from being washed away before it had time to set. This caisson was built by driving square piles about eight feet apart and placing shutters^or panels of plank between them. It was not in- tended to shut out the water, but to prevent currents from washing the concrete, and to give the concrete shape and hold it in position until it had become hardened or " set." The spaces between the round piles were than filled in with small stone, to about sixteen feet below mean low water, the outside of the caisson being embanked at the same time and to the same height with rip-rap stone. The interior of the caisson was then filled with concrete, lowered through the water in a box, and deposited by opening the box near the bottom, and allowing the concrete to fall out upon the small stone lying between the piles, and upon and around the piles, to the height of about twelve feet, or two feet two inches below mean low water. At this point the top of the concrete was levelled to receive the first or bottom course of the granite facing, which was then laid, course by course, to the top of the wall, the concrete backing being also raised to correspond with the courses of granite as each was laid. Having taken care by instructions as to details, and by sending Diver McDonald down under water to place every box of concrete in its pro- per position as it was lowered under the water, I examined the wall already built under New Pier No. 34. Passing under the pier in a boat, I found that all the square piles of the caisson had been removed, but only three of the shutters or panels, or about twenty-three feet out of ninety. All the other shutters were jammed against the face ot the wall by a mass of rip-rap stone, piled against them to an average height of about seven feet below mean low water. They never have been removed, and the face of the wall has never been properly exam- ined, nor can it be until the stone and panels are removed. The stone lying against them are too large to be moved by the divers (they estimate some of them to weigh nearly a ton), and some device with steam power must be used to remove them. Upon questioning Diver McDonald as to the examinations made by divers of the face of the wall, he informed me that he had made all the examinations under water up to date, and they consisted of an examin- ation of only one panel (about eight feet) out of ninety feet of wall built and lying under the pier ; that on this one panel he had found the face of the concrete wall good, smooth, and hard, for about six feet down from the bottom of the granite, but below that the concrete had fallen away from the mass, and the face curved in, and back from where it should be, till it reached the piles, when it just covered the second row of piles from the front (a distance, of over two feet), and leaving the 7 front row of piles bare of concrete and useless, not supporting the wall in any way. By the falling off of this outer bottom face of the wall, its tendency to rotation, or rolling over, is vastly increased, and especially so when the earth filling or embankment is placed behind it. In this particular case, however, the pier being built against the face of the wall will probably prevent any such disaster. I directed Diver McDonald to go down and carefully examine as much of the face ot the wall as he possibly could. He did so and re- ported to me that the three panels near the southerly side of the pier were all that he could get at ; one of them he had examined before, and they were all, extending over a distance of 22 or 23 feet, in the same condition of the one previously examined and above described. This is all that has been examined of that part of the wall under New Pier No. 34. The removal of the rip-rap stone in front of the re- mainder of the wall will be a work of some time. Its condition may be better than that part examined, or may be worse. That part of the wall directly north of New Pier No. 34, being under construction, was completed to the level of the base of the coping. On the 25th August, a crack was discovered just north of New Pier No. 34, and upon applying the instruments, it was found that the wall had settled about ^ of an inch at a point 78 feet from north side of the pier, and prortionately between said point and the crack, and that it had moved out, or westwardly, at the same point about the same dis- tance. Two shutters or panels were taken up on the face of the wall, about 60 feet north of the pier, and the Diver McDonald sent down to exam- ine. He reported the face of the wall good, smooth, and hard, for 10 feet 8 inches down from base of granite ; from that point down, the small rip-rap stone, intended to be placed between the piles, and not higher than two feet below their tops, lay under the concrete, and ex- tended down to the tops of the piles, and below the tops of the piles between them. These stones were wedged between the overlying mass of concrete and the top of the piles, so that at this point the weight of the wall rests upon a pile of broken stones, lying on top of and around the piles. This condition of things is not due to the principle of con- struction, but is directly contrary to it, and is the result of carelessness in doing the work. A diver should have been sent down to remove the stone, and see that they were in proper position before the concrete was deposited. No more panels have been taken up as yet at this point. The tctal extreme settlement to date is, 12-100 of a foot, the move- ment outwards 9-100 of a foot. The Diver McDonald has also examined about 40 feet of the rear of the wall at Canal Street, and found it in pretty good order. From the rear, however, a piece of concrete about 3 feet long, 12 inches to 8 15 inches wide, and 6 inches thick, had fallen off, and was brought up by him. This piece is all that has been obtained as yet from below low water mark. It is a very poor specimen of what concrete should be ; there is very little cement to be seen in it, and it has so little cohesion that it broke into several pieces by being rolled over, and could be readily crumbled and broken to pieces by the hand. It is preserved in the Canal Street office. The King Street section, 180 feet long, was completed as it now stands before my accession to the office ; it was built on the same gen- eral principle as the Canal Street section, but much more care has evi- dently been taken in its construction and details than at Canal Street section. Diver McDonald was kept under water, and tripped every box of concrete, and saw that it was placed in its proper position ; its faults and failures are, therefore, in my opinion, due to its being con- structed on a wrong principle. This wall was first examined in three panels of its face by diver McDonald ; one panel near the southerly end, one at the northerly end, and one about the middle of the section. Mr. Kid, Assistant Engineer in charge of the work, also went down in armor and examined the same three panels. They reported the two southerly panels smooth and soft, but at the northerly panel the con- crete face of the wall had fallen away from top to bottom to a depth into the face of the wall of from nine inches to fifteen inches, and that the concrete was soft where the face of the wall had fallen away. This wall having been recently completed, I suspended the removal of the panels for several weeks, in order to give the cement time to set if it would do so. All the shutters or panels on the rear of the wall were then removed, and most of those on the front. Diver McDonald went down and examined the wall, panel by panel, coming up and reporting the condi- tion of each ore before going to another. He reported the whole of the concrete wall soft, so that he could pull out stones with his hands, and various imperfect places, but not of great depth except in one or two places, including the above-mentioned. I then sent for Diver Gil- lihan, employed at the Battery, and directed him to go down and exam- ine the whole face of the wall, front and rear, where he could get at it. His report agrees generally with that of McDonald. He describes the softness such that he could dig into the wall almost anywhere by pulling out the stones of the concrete with his fingers, and that he did so dig in about eight or nine inches. He differs about the details of roughness and holes in the concrete wall, and it must be remembered that the diver is unable to see any- thing while under water (on account of the foulness and muddiness of the water), and his examination can only be made by feeling with his hands under water and in total darkness. A complete agreement of 9 reports of examinations made under such circumstances is, therefore, not to be expected. In regard to the plan of driving piles to such depth that their heads should be fourteen feet under low water mark, by a follower, and plac- ing concrete upon them without cutting off or squaring their tops, I thought it impossible that any piles driven so hard as they must be, for such a purpose, could be in a fit condition to bear the weight of the wall. I therefore procured a pile-cutter and had the heads of the piles just driven at Clarkson Street section cut off, at a depth of about fifteen feet below low water. The result proved as I had anticipated. The pile heads, as they came up, when sawed off, were split into several pieces, broomed up, and damaged so as to be unfit for bearing any weight whatever. A record was kept of each pile head, showing the position of the pile from which it was cut, and its condition as to being split or broomed up. The proportions were — one-half in very bad condition indeed, one- sixth in bad condition, and the remaining one-third of the whole in pas- sable order. The pile heads were all saved, and can be seen at Clark- son Street, and also at Canal Street, south of New Pier No. 34, where they have just been cut off in similar manner, and with same result. There is no doubt whatever that the pile heads must be cut off in all cases, before placing any weight upon them, to a good and solid part of the pile, so that the wall may rest upon a firm and solid bear- ing. The facts ascertained in my examinations thus far as described above, and consisting principally of the softness and want of cohesion of the concrete in the King Street section, the falling off of whole panels to the depth, on the face of the wall, of from nine inches to fifteen inches from top to bottom, the falling off of the lower half of wall to the depth, on its face, of two feet at the Canal Street section, and the condition of the piece of concrete brought up from the rear of the Canal Street section, indicate clearly that the plan of building the wall of concrete placed under water " en masse," " in situ," cannot be relied upon to produce a permanent, stable and durable wall ; and I am under the necessity ot recommending at least the suspension, if not the entire abandonment, of such plan. No wall has been built upon this plan since my accession to office, except that part of the Canal Street section begun before I was appoint- ed, and since then completed. The work of building the bulkhead wall is now suspended by my orders, and I shall desire to have the approval the Board of my action. In consideration of the fact that this plan of building the wall is highly commended in the report of the late Engineer-in-Chief of this Department, dated 1st June, 1875, and that such report has been made 10 public, and extracts from it printed in the newspapers and in Van Nos- trand's Engineering Magazine, I beg leave to suggest to the Board of Commissioners, through your Committee, the propriety, for the justifi- cation of the Commissioners and of myself, of calling to our assistance the united wisdom and experience of disinterested engineers, to examine the condition of that portion of the wall referred to in this report, and advise what remedy, if any, should be applied to it. Very respectfully, Your obedient servant, G. S. GREENE, Jr., Engineer-in-Chief. 11 New York, Dec. 17th, 1875. To the Commissioners of Docks, New York City : Gentlemen ; — We have the honor to submit this preliminary report with respect to the condition of the Bulk-head Walls at the foot of Canal and King Streets, North River, upon which our opinion was solicited. The scope of inquiiy submitted to us is briefly set forth in a com- munication addressed to us by His Honor the Mayor, dated Oct. 12, 1875, and is comprised in the following extracts, viz : " You are requested to make an examination of the bulk-head walls, " now partially constructed at Canal and King Streets, North River, "and report to the Department of Docks, at the earliest day prac- " ticable, the facts as to the condition of such structure, together with " your opinion as to their safety and durability." " You are requested also to communicate your advice as to com- " pleting such structures, either with or without modification of the " plan of construction ; and to give your advice as to what, if anything, " should be done with those structures." We were further requested by your Department in a communication dated the 8th inst., to express definitely our opinion " in regard to the system employed in said constructions." On the receipt of the Mayor's communication, we immediately entered on our duties, and commenced an examination of the King Street and Canal Street bulkheads, the Department of Docks having previously sunk a shaft in the centre of the King Street bulk- head, and constructed and placed a three-sided caisson against its face. We have now, with the aid of divers made thorough examinations of all the exposed faces of both bulk-heads, the examinations of important points being by two divers at different times, thereby checking their reports. The water has been pumped out of the caisson and the shaft at King Street, and we have made a personal examination of the exterior face and centre of the wall. We have also had a shaft sunk in the centre of the Canal Street wall, and have had a caisson constructed there, in which we are making trial of concrete construction under as nearly as possible the same conditions as those under which the bulk- head was made ; in fact a model on a large scale of the wall itself. When the concrete shall have become sufficiently set, the caisson will be raised, and the condition of the concrete can be readily examined. 12 We are also having experiments made of the comparative set and strength of concrete of Portland and Rosendale cements, in the position and under the circumstances obtaining in the construction of the bulk- head. All these experiments require time for the setting of the cement, and are at present incomplete. We cannot therefore at present give a full answer to all the queries proposed, but in answer to your first interrogator)', "the facts as to the co7iditions of such structures, together with your opinion as to their safety, and durability," we would respectfully report that, from all our examinations, we find that the mode of construction adopted, in connection with the details, appliances and materials used, is uncertain in its results. We have found that the component parts of the concrete, have settled in layers, or strata with varying proportions of cement ; that the broken stone and sand are in excess at the bottom of layer, and the cement at the top ; that the cement has washed out and deposited itself as laitance, in combination with the soil in the water in layers by themselves, presenting the appearance of seams between the different layers of concrete, or of pockets in spaces in the concrete. Many portions of the wall we find strong, with a good set, but the faces almost invariably weak and the set imperfect ; but we do not find any but the slightest settlement or delignment of the wall, nor is it probable that either of these will increase to any injurious or unsightly extent, whilst the bulkheads remain under their present conditions, without back-filling. But, before the earth filling is put in behind the walls* we should propose some further protection against the thrust outwards of the embankment. Whatever of weakness there may be in the present structures we think it may be remedied without any removal of structure or any large expenditure. We would propose at any rate to leave it as it is for the present. We do not wish to be understood as condemning, as a system, the method of constructing submarine masonry by passing mixed concrete through and depositing it in the water. On the contrary, it is well known that excellent work can be executed in that manner, under suitable precautions in respect to the quality of the cement used, the proportions of the cement to the coarse ingredients, the kind of apparatus employed in laying it, and the care with which it is operated. Our criticisms will be more fully set forth in our final report, and will refer to the details of the method of construction adopted for the Canal and King Street sections. Our final report, which will give in full all the facts obtained in our examinations, with the results of our experiments, will be completed within the coming month. In it we will endeavor to give satisfactory answers to all the interrogations submitted to us, and we suggest that 13 nothing be done in the meantime towards completing those portions of the walls for which the pile foundation has been wholly or partially prepared. Very respectfully, Your obedient servants, JOHN NEWTON, Q. A. GILLMORE, WM. E. WORTHEN. 14 New York, Feb. 18, 1876. To ti*£ Commissioners of Docks, New York City: Ge7itle?7ien : — We have the honor to submit below our final report on the bulkhead or quay walls, now partially constructed on the water front of this city at the foot of Canal and King Streets, North River, embracing a statement of our views and opinions upon the various questions submitted to our consideration as set forth in the instructions received from His Honor the Mayor, in a communication dated Oct. 12, 1875, and from your President in a letter dated Dec. 8, 1875. In appendices to the joint report, but forming a necessary part thereof, there will be found separate reports or notes of the inspections made by us individually of different portions of these walls. Those notes of inspection are accompanied by such remarks, explanations and suggestions as the inspector thought proper to make, and for which he alone is responsible. DESCRIPTION OF THE WALLS. Quay Wall, Foot of King Street, N. R. In the monolithic concrete base of the river wall, at the foot of King Street, North River, there were used 1,546 barrels Portland cement — mostly "White's," but some of several other English brands, 9,963 cubic feet sand, 24,678 cubic feet of concrete stone (trap-rock.) Omitting small fractions, this gives the proportions by volumn of 1 cement to 1 6-10 of sand, and 4 of broken stone. To this there was added, while laying the concrete,' 2,403 cubic feet of rubble-stone of random sizes, varying from 6 to 12 inches in longest diameter, distribu- ted as uniformly as possible through the mass. The concrete was lowered through the water in a box of 2 cubic yards capacity, opened on one side when it reached bottom. The box was wedge-shaped, such as would be formed by cutting a cube into two equal parts, by passing a plane through diagonally opposite edges. It had no cover on the top, so that the top surface of the concrete was subjected to wash in its descent through the water. The height of the concrete base varied from 9 feet 9^ inches, to 14 feet 9^ inches, the average vertical thickness being 12 feet 4^ inches 15 This base is underlaid by a bed of rubble-stones, but it rests upon piles surrounded by the rubble, as hereinafter described. The piles are driven in eight longitudinal rows, those of the front and rear rows being placed as close together as possible, while in the other six rows they are 2}/ z feet apart between centres. Transversely the rows are 2.y 2 feet apart between the centres of piles, except the three rows in front, under the toe of the wall, which are 2 feet apart between centres. The piles were driven with a follower, and, with the exception of those in the front row, were not cut off after driving. The heads — many of them badly split and broomed up — were on different levels, their average depth below mean low water being 13X feet. The bed of rubble-stones which surround them has a vertical thickness of 8 feet. It was roughly leveled off when laid, at an average depth of 14 57-100 feet below mean low water. The pile-heads therefore project above the rubble an average distance of 1 34-100 feet, the greatest projection being 5 feet, while 13 per cent of them, inclusive of the front row, have their heads on a level with the rubble-stone around them. The con- crete base, which was laid in a wet caisson constructed after the foun- dation piles were driven, is 18 feet six inches thick at the bottom next the rubble-stones, and has a batter of 1 ]/ z inches to the foot on the face and y 2 inch to the foot on the back. The top surface is roughly leveled off at an average depth of 2 feet 2^ inches below mean low water. That portion of the wall above the concrete base, including the coping course not yet laid, is 12 feet high, has a cut granite face, laid in six courses, of which five, omitting the coping, are alternate headers and stretchers. The back is of built-up rubble-blocks, and the heart- ing is concrete from in situ. The granite face sets back 6 inches from the edge of the concrete base, and has a batter of 1 inch to 1 foot ; the rubble-blocks in rear are in two courses, each 4 feet 8 inches high, the lower course being set so as to leave a concrete berm 6 feet wide, thus giving a thickness of 9 teet to the base of this superstructure. The second course of rubble- blocks is set with an offset of 1 foot, its upper surface being at the level of the base of the coping course. The granite coping course is to have a rise of 2 feet 6 inches, and a thickness or width of 4 feet. A transverse section of the wall and foundation, taken where the bed of mud overlying the bearing stratum of clay is the deepest, is shown in Fig. 1, Plate I. Fig 2 shows a plan of the wall. At the foot of the wall, in front and in rear, a bed of rip-rap stones was formed, simultaneously with the bed of rubble-stones around the pile-heads, and intended, in conjunction therewith, to secure the piling 16 against lateral motion, and particularly against outward thrust from the earth rilling, in rear of the wall. Diary of Construction. The site of wall was dredged out between Nov. 16 and 23, 1874, inclusive. Took out 3,600 yards of soft mud. The foundation piles were all driven between December 1, 1874, and January 14, 1875, inclusive. The false work for the caisson, including inclined square piles and shutters, was constructed between March 16 and April 20, 1875, in readiness for the 4-inch stone around foundation pile-heads, and the rip-rap outside in front and rear. The piles were centred 8 feet apart longitudinally. The 4-inch stone around the foundation piles was all put in between April 17 and May 5, 1875. The total quantity was 788 cubic yards, spread over an area of 146^ by 17^ feet, giving a vertical depth of over 8 feet. The rip-rap outside in front and rear, was filled in and brought up simultaneously with the 4-inch rubble filling. Putting in the rip-rap began April 19, 1875. 1,504 cubic yards of rip-rap were placed in front, and 1,138 cubic yards in rear. May 28th, commenced laying concrete, the instructions being not to allow the proportion of sand to exceed : cement, 1 ; sand, 2 ; and stone, 5. The first or lower course was filled to an average thickness of about 2 feet, just covering the pile-heads along the middle line, and about 3 feet higher at the sides against the shutters, thus presenting a concave surface on top. The first course was laid between May 28th and June 5th, inclusive, for the entire length of the section equal to 146^ feet at bottom, between the cross bulkheads at each end. This lower course rests directly on the pile-heads, and on the 4-inch rubble-stones between them. The second course, about 5 feet high, was begun June 7th, and as soon as the laying cf the lower course was finished. About June 15th, third course, about 5 feet, was begun, and on that day, for a length of three panels at north end, was carried up to within a few inches of the level required for lower course of granite. By June 1 8th, a length of eleven panels, or 88 feet, was carried up to same level. On June 23d, begun the 4th, or top, course of concrete by lowering 17 the concrete in an ordinary water-bucket. This top layer was simply a leveling, of course, and was only a few inches thick. June 24th, commenced to set granite and rubble-block backing, and the concrete hearting at north end. July 3d, the concrete monolith was finished. The laying of the granite commenced June 24th, being in progress elsewhere. On July 7th, finished the wall to present condition, in readiness for the coping, the rubble-block backing and the concrete hearting having been carried up simultaneously with the face of the wall. The rip-rap apron, front and rear, was widened after this date, but is not completed to present date. On July 21st, commenced taking up the shutters, and between that date and September 15th, twelve shutters were taken up in front and seventeen in rear, in which condition it now remains. While laying the concrete, a diver was down nearly all the time every day, and actually adjusted the position and tripped the box for about one-half the work. At the time when the examination was made in October, 1875, tnat portion of the concrete foundation first laid had been in place nearly five months, while the different parts of the top course had been down from three and a-half to four months. Quay Wall Foot of Canal Street, N. R. The description hereinbefore given of the traverse form, dimensions and method of construction of the wall at the foot of King Street, applies also to the wall at the foot of Canal Street, with the following exceptions : 1st. The concrete base is 18 feet thick at bottom at the level of the rubble-stones. 2d. The superstructure is 10 feet thick at the base when it rests on the concrete. 3d. The box used at Canal Street for laying the concrete under water, although of the same form and arrangement for tripping as that employed at King Street, was only half as large. It held one cubic yard, and like the other had no cover on top. 4th. The proportions adopted for the concrete were for the lower 2-foot layer, 1 barrel Portland cement, 2 of sand, and 4 of broken stone. For a portion of the second layer (4 feet) the proportions were 1 l /z Portland cement, 2 sand, and 4 broken stone ; but this was soon changed, and for the rest of the entire work the proportions for the 18 front were \ x / z cement, 2 sand, and 5 broken stone and for the rear 1% cement, 2 sand, and 5 broken stone. Fig. 1, Plate II., shows a transverse section of the Canal Street wall and pile foundation, taken at a point where the bed of mud is the deepest, through which the piles have to pass before they reach a holding stratum. Figs. 2 and 3 show, respectively, a plan and eleva- tion of the wall. Diary of Construction. September 11, 1874, commenced dredging the site. October 6, 1874, finished dredging. During this interval, there were removed 1,400 cubic yards of stone (old crib from Pier 42^), and 9,050 cubic yards of mud, giving an average low water depth of 20 feet. October 20, 1874, commenced driving foundation piles, spaced exactly like those of the King Street wall. The .front row was cut off by November 16th at the level of 14 feet inches below mean low water, all the piles in the eight rows being driven with a punch to different levels, as at King Street. By December 4, 1874, all the square piles for false work were driven for 193 lineal feet of wall, and 239 cubic yards of rip-rap stone placed in front under and a little to the south of Pier 34, and 466 cubic yards of 4-inch stone, and 98 cubic yards of smaller stone placed between the piles, to an average depth of 4 feet. It was rammed by a long- handled rammer, worked by three or four men above. December 24, 1874, commenced concreting 55 feet south of south line of Pier 34, and worked up to north line of Pier 34, with the lower 2-foot layer. January n, 1875, finished this first layer. March 17, 1875, commenced second layer 4 feet thick, and followed it with another 4-foot layer, and on April 5th, commenced with the top or trimming layer of 2 feet. May 4th, commenced laying first course of stone ; and on May 22d, finished 100 lineal feet of wall, except the coping course. This portion extends from north side of Pier 34 100 feet south, rack- ing off in offsets at each end for future construction. The coping course has not yet been set, and will not be required under Pier 34, which covers 90 feet in length of the wall. North of Pier 34. By July 9, 1875, the portion of the Canal Street wall, north of Pier 19 34. was got ready for laying the lower 2-foot course of concrete around the pile-heads. Between July 9 and 26, 1875, placed concrete base for 50 lineal feet of wall in extension, north of Pier 34, ready for stone. July 27th, commenced laying stone on this 50 lineal feet. By August 20, 1875, the wall was finished to its present condition, the coping being omitted ; the portion north of Pier 34, being 112 feet long on the bottom, and 87 feet long on the top of fifth (E) course. For that portion of the concrete base south of the north side of Pier 34, only Knight, Bevan & Sturges's cement was used. For the 50 feet north of the norch side of Pier 34, the greater por- tion was White's, with Knight, Bevan & Sturges's on the face of wall. For the additional 62 feet north end, Burham & Gillingham's cement was used, with probably some of White's. At the time of inspection, the age of the concrete in that portion of the base under and south of Pier 34, ranged from six and a-half to ten months, while the part last laid on the north end of the section was from two and a-half to three months old, before the inspection was com- pleted. In order to test the qualities of Rosendale and Portland cement under the same circumstances of exposure, mixed with different proportions of sand and broken stone, eight varieties of concrete were deposited in casks under water January 3d, and taken out and examined January 2f, 1 S76. The casks were of forty-five gallon capacity, and were pierced with i-inch auger holes on all sides, the holes being 3 inches apart between centres horizontally, and from 3 to 5 inches apart vertically. The bot- toms were pierced in a similar manner, the holes being 3 inches apart between centres both ways. Four-inch rubble-stones, of the kind used around the pile-heads under the Canal and King Streets walls, were then put in the bottom of each cask to the depth of 9 to 10 inches, and they were then set in the water alongside of the wall at the foot of Canal Street, so as to be entirely submerged, the tops of the casks being about 6 inches below the surface of the water. The concrete, as soon as mixed, was taken up with shovels and deposited in the several casks until they were filled, one after the other. The shovelful of concrete was in each case passed through the water until it reached the place of deposit, when it it was tipped so as to allow the concrete to slide off. In this condition they were left for eighteen days, constantly sub- merged, with the exception of two or three occasions, when they were partly out of water for a short time. On January 13th, at 3 P. M., when the temperature was several degrees below the freezing point, the tide fell about 18 inches below the tops of the casks. Subsequently, their tops were again exposed, for about 6 inches. 20 On the eighteenth day after immersion, they were all raised, opened on the sides by removing several staves, and carefully inspected by cutting into the body of the concrete. The kinds and proportions of materials used in each cask, and the condition of the concrete at the time of ex- amination are given below. The Portland cement was the kind used in the foundations of the Canal and King Streets walls, and of good quality. The Rosendale cement was manufactured by F. O. Norton. It was selected from his stock on hand, some of it being rather quicker set- ting than the rest, though not conspicuously so. Number One. Portland cement, measured dry 3 volumes. Sand, measured damp 5 Broken stone 10 " This concrete was in all respects like the best quality used in the foundations of the Canal Street and King Street walls. On examination, the cement and sand were found to be badly washed out from the broken stone on all sides next the barrel, and in the lower portions next the rubble-stones, leaving numerous voids in the mass. Considerable sand and cement were found among the rubble at the bottom of cask, and some had evidently washed out through the auger holes. Where not washed out, the set of the concrete was pretty good. Near the top of the cask the concrete was free from voids, and of much better quality than below. The set was quite hard on top. Number Two. Portland cement, measured dry 2 volumes. Common lime, slaked to powder 1]^, '* Sand, measured damp 5 " Broken stone 10 " The cement and sand were badly washed out all around next the cask, and also, to some extent, but not so badly, through the mass. Poor set next the cask, but good set in middle, away from the wash. Very little mortar left among the stone next the cask, for about 3 inches all around. Set somewhat better than in Number One, and sand re- tained better in the heart of the mass. Number Three. Rosendale cement, dry iy 2 volumes. Damp sand 5 Broken stone 10 Cement and sand washed out around outside, next the cask, but not 21 badly. Also, washed out for so.ne distance above the large rubble- stones. Very little set, except in the upper portions. Too much sand was used in the mortar. Number Four. Rosendale cement, dry 4 volumes. Common lime, slaked to powder 1%. Damp sand 5 " Broken stone 10 Main bulk of concrete good, and no washing out of the cement and sand except a very little at bottom next the rubble-stones. The mor- tar retained its constituents throughout the mass, and there were no voids, except at bottom as above noted. Good adhesion of mortar to stone, and a very good set. Concrete satisfactory. Number Five. Rosendale cement, quick-setting 5 volumes. Damp sand 5 - Broken stone 10 " The same remarks apply to this concrete as to Number Four, except that it had set a little harder, and on that account might be pronounced a little better. Number Six. Slow-setting Rosendale cement, dry . 5 volumes. Damp sand 5 " Broken stone 10 " Very little sifting or washing out of cement and sand, and very good concrete. The set was satisfactory, and the mass well held together. Number Seven. Slow-setting Rosendale cement, dry 4 volumes. Common lime slaked to powder 1% " Damp sand 5 " Broken stone 10 " Very little cement and sand washed out, and that only close to sides of cask, and directly next the rubble-stones. No voids in concrete elsewhere. Good adhesion of mortar to stones, and very good concrete as a 22 whole. Set not quite so good as in Number Five. Cask well filled out all around. Number Eight. Slow-setting Rosendale cement, dry 4 volumes. Quicklime (not slaked) - 1 " Damp sand 5 " Broken stone 10 The cement, sand and lime remained well mixed, and there was little, if any, washing out from among the stones. Some traces of lime, but no sand, among the rubble-stones below. There was very little set in the concrete. The best out of these eight kinds of concrete are Numbers Four, Five, Six, and Seven. There being very little difference in the hydraulic activity of the Rosendale cement used, Number Four should give the same result as Number Seven, and Number Five the same as Number Six. So little difference was exhibited among these four specimens, that the propriety of cheapening the concrete by replac- ing a portion of the cement with common lime cannot be doubted. DESCRIPTION OF CAISSON. [See Plate III.] It was judged expedient by committee that a large box or caisson should be constructed, and sunk beneath the water, in which should be deposited the same materials as those used in the construction of the wall — in the same proportions, and under, as nearly as possible, the same conditions — making a fac simile of the lower part of the wall, which could afterwards be raised out ot the water and examined. The size of the box was limited by the capacity of the largest derrick, and the total weight of box and contents was estimated at from 80 to 85 tons. The interior area of the box was about 10 feet square, but the platform on which it was supported was 16 feet square. This platform was composed of timber, 12' x 12', placed about 2 and 3 inches apart, extending lengthways of the wall. On these timbers there was a 2-inch tight plank platform. And on the outer edges of the timbers there were timber sides also 12' x 12', 3 timbers high on all sides, making a complete box, about 3 feet high ; there were small interstices between the timbers, crossing the lower timbers. On the other sides, where the timber sides were parallel with the bottom timbers, the central timbers were cut to about 7 feet in length, and 23 placed in the centre of the sides, so as to leave apertures of 3 feet by 1 foot at each end. These sides corresponded, when in position, with the river and rear faces of the wall, where there should be more circu- lation through the broken stone base, than at the other sides, which represented lines of cross sections of the wall. Within the timber sides, furring blocks were spiked of about 1 foot in width, to which were nailed 3 2-inch planks,with about 1 inch inter- stices between them. These planks formed a box about 10 feet square and 3 feet high, and enclosed the space which was fo be filled with broken stone. Inside this box were set piles of 12 to 15 inches diame- ter, and from 3 feet 6 inches to 4 feet 6 inches in length ; the front row — that is, those which were to be on the front line of wall or river-side, were 8 in number and placed almost close together, and were sawed off to an uniform height of 4 feet above platform. Between this row and the next 2 in the rear, the spaces between the piles were about 18 inches, and between the 3d and 4th or last row, the space was about 2 feet 6 inches. The 2d, 3d and 4th rows consisted of 4 piles, each of various heights, some with sawn tops, others as they had been cut off from piles already driven and left broomed at the top. These piles were placed laterally about 2 feet 6 inches between centres, and all were strongly spiked to the platform with little short braces, about 6 inches long at the bottom. There was no connection between the piles ; the spaces were left entirely free for the reception of the broken stone. In front of the front row of piles, there was a space of about 2 inches between the piles and the planking, at the rear and sides about 6 inches. Above the 3-foot box, a tight plank box was made about 6 feet high, with a sloping face in front corresponding to that of the wall. At the sides and rear the faces were vertical. The lower timbers were securely bolted to the side timbers, and 4 strong eye-bolts extended down through the side and bottom timbers. The frame was rigid ; and by chains attached to the eye-bolts, the caisson could be readily raised and deposited in place. The position chosen for sinking the caisson was on the line of the Canal Street dock, nearly opposite the mouth of the Canal Street sewer. The limits of our investigations were the King Street and Canal Street docks, to determine whether these structures were reliable, and if not, what should be the form of the extension of these structures, on the foundations already prepared. At Canal Street, the pile foundation was already in and cut off nearly level, affording a secure base for the support of the caisson. No so convenient a site could be secured at King Street, and accordingly the caisson was loaded with broken stone and sunk at Canal Street, with its sloping face toward the river, and on the line of the wall. The broken stone was placed in under the direction of Mr. Radenhurst, the Engineer, who had had charge of the 24 construction of the Canal Street dock, and levelled off to the height of about 3 feet above the platform. Word was then sent to the Com- mittee of the readiness for the deposit of the concrete. The Committee attended November 12, 1S75, and there were present a portion of the time, Gen. Graham, the former Engineer, and Mr. G. S. Greene, Jr., present Engineer of the Department of Docks. Mr. Radenhurst took charge of the work, assisted by the same fore- man and many of the workmen, who had previously been employed in the construction of the Canal Street dock. The Committee themselves gave no directions as to the detail of the preparation of the material, or the manner of the deposit, but took full notes of the work as it was done. Their directions to Mr. Radenhurst were to make as nearly a fac simile of the concrete wall of the dock as possible, using the same proportions of cement, sand and broken stone, the same trip-bucket, and discharging the same, with the usual fall through the water. On the I2:h, 14 batches ot concrete were deposited, consisting of one barrel of Portland cement, two barrels of sand, four barrels of broken stone, each. This corresponded with proportions in the first layer of con- crete in the wall, which rilled in around and above the head of the piles. Soundings were made by Mr. Radenhurst of this layer after it was deposited, and the accompanying sections furnished to the Com- mittee. This layer was left to set till December 13th, when a second layer of six batches, consisting of 1 % barrel of Portland cement, 2^ barrels of sand and 5 barrels of broken stone, each ; and on December 14th, eight batches of the same proportions, as on the 13th, were deposited. On November 12th, the temperature of the water in the caisson was 51 Fahrenheit, and of the fresh water with which the concrete was made, 48 . December 13th, the water in caisson was 38 , and the fresh water was heated to 73 Fahrenheit ; on the 14th, nearly the same temperatures were obtained. The caisson was left undisturbed till January 17, 1876, when the 100-ton derrick was brought from the Battery, and the caisson was safely raised and deposited on the timber dock adjacent. The committee commenced the stripping off the plank and timber sides on the after- noon of the same day, exposing the rear face, which was photographed on the 18th (1) ; the loose stones at the bottom were then removed, and photograph (2) taken ; subsequently the planking and the timbers of the other sides were removed and photographs taken on the 20th, sufficient to show the condition of the concrete as it appeared on the removal of the sides of the box, and of the interior after it was broken into. The photographs (1 to 6 inclusive) are herewith submitted, with explanatory references. The faces of concrete, as marked on the photographs, designate their 26 ity. There were layers of concrete made up of varying proportions of sand and cement, but sand always in excess ; some with so little cement as hardly to be considered concrete, and others, where the set had become very good, and could only be detached in masses. The first layer around the head of the piles in the interior of the caisson had a very fair set, but the layer directly above it, deposited December 13th, and from 6 to 9 inches thick, was by far the best concrete in the mass. As a whole, although there is in the mass some extremely fair and well-set concrete, it is not sufficiently homogenous to be considered a monolith ; and the exterior faces — where, in construction, they would be most exposed — are weakest and worst. When cement like this is used, and the concrete deposited in water, there seems to be a tendency in the cement to separate from the mass, and the smaller the mass in which it is deposited and the deeper the water in which it is discharged from the bucket, the greater the likelihood of separation. The deposit of each day is marked by a layer or seam, which probably might be removed by washing, but has not been in the construction of which we have made an examination. It was our instruction to make the caisson, as near as possible, a sample of the wall as built, and, on its face, it exhibits the same denud- ing of the outer row of piles, the same seams, and sometimes larger deposits of washed cement, dry and loose stones, and sand in excess. In the interior, the caisson exhibits seams greater in width than those in the Canal Street dock shaft, with deposit of sewerage ; but the concrete around the head of the piles, and directly above the first seam, is of the same general character in both Replies to Official Communications. Our original instructions, as contained in a letter from His Honor the Mayor, bearing date Oct. 12, 1875, are as follows : " You are requested to make an examination of the bulkhead wall now partially constructed at Canal and King Streets, North River, and to report, to the Depart- ment of Docks at the earliest day practicable, the facts as to the condition of such structures, together with your opinion as to their safety and durability. " You are requested also to communicate your advice as to completing such structures, either with or without modifications of the plan of con- struction ; and to give your advice as to what, if anything, should be done with those structures. " For general details of plans, and for the proper facilities to enable Mm ZD o < u. z w I- u 5 3 UJ O Q 5 _| cO O < UJ o: O X u. p o Q Ct ? UJ uj > > O uj 2 i UJ |- z UJ — it l— UJ 00 (J cr UJ > 27 you to prosecute your examination, you are referred to the Department of Docks, and are requested to communicate with the President and Commissioners of that Department, and to act under their directions." Agreeably to this request, we waited on the President and Commis- sioners of the Department of Docks, and all the records of the De- partment, with reference to the construction of the bulkheads, were submitted to us, and the Chief Engineer, Mr. George S. Greene, Jr., was directed to furnish us every facility in our investigations. The former Engineer-in-Chief, Gen. Charles K. Graham, sent us copies of his report on these structures, and from time to time has cor- dially met us, and explained the design of the work and the directions given for its prosecution. The Assistant-Engineers, Messrs. Raden- hurst and Kid, having had immediate charge of these constructions, have assisted at our examination and experiments, and given us the details of construction. We preface our report with a brief sketch of these structures, drawn from the records of the Department and from reports and excerpts from the diaries of the engineers in charge of construction. We append the facts obtained from our own examinations. The examinations of the exterior faces of the wall could only be done by divers ; two were employed, neither in the service of the Department, and the reports of one were checked by those of the other. Every panel in the front and rear of the King and Canal Street walls, which was exposed, was examined, holes were drilled, and speci- mens of material brought up for our inspection. We have had a caisson constructed and submerged, in which con- crete has been deposited, of the same proportions of cement, sand and ' broken stone as that of the bulkhead at Canal Street. This, after an allowance for the setting of the material, has been raised and deposited on the dock, as a probable specimen of what the bulkhead wall might be. We have had shafts sunk in the King Street and Canal Street walls, for a personal inspection of their interior condition ; and a three-sided caisson has been fitted to one of the panels of the King Street dock, and freed from water, to give us the same partial inspection of its face. We have made experiments on different kinds of cement, in different proportions of cement, sand and broken stone, deposited in submerged barrels, with reference to the material to be recommended in future construction. All the above are given fully in detail. It remains for us to make our deductions from facts thus obtained and reply to the request of His Honor the Mayor. ist. " As to the safety and durability of these structures." In our opinion, as structures we cannot consider them as safe and durable in •is their present condition, nor with the further precautions intended by their designer ; and for the following reasons, viz. : The foundation is composed of 8 rows of piles driven vertically, the front and rear rows being set as close together as possible, with a layer of broken stone — intermediate — between the piles, and aprons of sim- ilar stone in front and rear, as already described. The length of the piles under the King Street bulkhead averages about 50 feet, measured from the " formation level," at the bottom of the concrete base. The upper stratum is represented as "dock mud," the lower 20 feet as "tenacious mud," and the base on which the pile rests as " clay and sand." The length of the piles beneath the Canal Street bulkhead is 30 feet, measured from the same level as above, resting on the same base of clay and sand, with a depth of " tenacious mud " overlying of from 6 to 19 feet, and an upper stratum of" dock mud." We are obliged to assume, for the sake of safety, that the base of these walls is virtually somewhere within the stratum of " tenacious mud " and near the " clay and sand " base. We do not concede that the aprons of broken stone or rip-rap, placed at the level of the pile-heads, have the effect to transfer the base of the structure from the lower to the upper ends of the piles. A constant pressure from behind may move out the entire mass of stone by sliding it forward in the layer of " dock mud " on which it rests ; under this assumption, it would not be safe to rill behind these walls with earth to the level of the top of the coping. Your late Engineer-in-Chief, Gen. Graham, in order to relieve this thrust from the back-filling, drove seven rows of piles, spaced feet between centres in the rear of the wall, and we understand it was his intention to stay the tops of these piles by ledger plank, strongly spiked, just above low water level. Although this system of piles might answer a temporary purpose, we do not consider this method sufficient to relieve the thrust and insure the safety and durability of the wall. Of the imperfections of the mass concrete around and above the piles, the details are given in the divers' reports and examinations, it is only necessary to state its condition in a general way. The river face of the King Street bulkhead has fallen off badly and caved under at the toe in many places, denuding the top of the first row of piles, virtually reducing the base of the wall to 16 y 2 feet ; still there is a fair breadth of wall remaining, ample to resist all crushing strains, were there no other weaknesses of construction. At Canal Street, the river face is not as much exposed as at King Street. Many of the "shutters " are still in, and rip-rap and broken dockage cover much of the lower surfaces. When exposed, the face was found to be generally of an imperfect set, with well-developed soft 29 seams, some of considerable width, and extending deeply into the body of the work. But the concrete of the interior, as tested by a single shaft at both places, is better at Canal than at King Street. The back of the wall at both places, considering its position without exposure to wash, is fair. Besides the elements of uncertainty in both bulkhead constructions, arising from imperfect set, and separation of the component parts of the material, soft seams and abrasion of face, there is another in the condi- tion of some of the pile-heads in the mass of concrete. Whilst admit- ting the value of the extension of the piles up into the mass, and the binding and uniting qualities of the concrete among the piles, still, where a pile has been driven by a follower, and the top of the pile left broomed and broken, the obvious inference must be, that the head of the pile is injured for an insistent weight, and from the overhang of the head, the concrete may fail to enclose the bod} of the pile below\ As an apparent evidence of this, when, in the shaft at Canal Street, the top of a pile was reached, the water flowed in so freely around the pile that the work was suspended. Above the lower mass concrete, the granite river face and beton- block backing with concrete mass hearting are well massed, strong and permanent. Whilst thus giving the general imperfections of the mass concrete, its falling off from what was intended to be its composition, and the uncertainty of the elements on which calculations for stability may be based, it is proper to state that there is now no disturbance of alignment in the visible structure, no cracks that show dangerous settlement. Having decided against the stability and durability of these structures, we now proceed to comply with the second request of His Honor the Mayor—" to communicate our advice as to completing such structures, " with modifications of the plan of construction, and to give advice as to " what should be done with those structures." Where the granite wall is complete, with the exception of coping, we advise that the coping be laid both at Canal and King Streets. Where only the piles have been driven for the foundation, we advise that the first three row r s of piles, front and rear, and intermediate piles, sufficient for the support of headers, hereafter described, should be cut off at an uniform level from a permanent stage. We recommend the exterior faces, both front and rear, and headers of the foundation courses, to be made of rubble-blocks as prepared by Gen. Graham, or Beton-blocks. of width sufficient to bear on the the three rows of piles, front and rear for the stretchers ; and two transverse rows for the headers, to have suf- ficient rise or height to complete the foundation to the level of the A course in two courses. Both courses to be alternately headers and stretchers ; stretchers in such lengths as may be best adapted to the 30 derricks, say from 9 to 12 feet long ; headers to extend through both walls. The lower face of upper headers between the walls to be cham- fered at angles of 45 on each side to an edge at the centre, so that there may be no surface sheltered from the mass concrete hearting as deposited. The first layer of hearting on top of the piles to be of bags tilled with concrete in courses, which will adjust themselves around and enclose the heads of the piles, and make a strong and secure base. Above the bags, the space to be rilled in with mass concrete. As each course of upper headers makes a sort of box, the concrete is to be pre- pared in mass sufficient to fill this space, and deposited at once by a trimie. Of the material and proportions of which the blocks should be made, we see no reason to alter the proportions and material already adopted ; but for the hearting, we recommend the use of Rosendale cement, quick-setting, instead of Portland, with the addition of a little slaked lime in proportions 4 volumes cement, \% common lime slaked to pow- der, 5 sand, 10 broken stone. With regard to the wall above the concrete base as above, we recom- mend no change of the present construction. To resist the thrust of the back-filling we recommend that 1 1 rows of vertical piles, spaced to 3-feet centres, be driven in the rear of the wall at Canal Street, and 13 rows at King Street, with rows of interme- diate inclined piles ; the inclined piles to be driven at an inclination of 3" horizontal to 12 vertical, each row to be 3 in number; the first, or nearest the wall, to be so driven that the foot will rest near to and in the rear of the foot of the rear row of piles beneath the wall ; the 3d pile-head to be on a line with the last row of vertical piles — that is, the nth and 13th from the wall, as above. That a string-piece be securely bedded on the rear projection of the concrete mass, or beton-blocks. That the piles be cut off at a suitable level, so that their caps, notched to receive the head of the piles, may rest on this string-piece, the caps to be trunailed to the string-pieces and to the piles ; the planking to be 3" thick and secured to the caps by trunails. When the platforms are completed, the earth back-filling to be commenced at the wall or river side, and embankment face to be always preserved towards the shore or old bulkhead line. With a platform in the rear of the wall, of the extent proposed, thus supported, bonded, and back-filled, we should feel confident of the security of the whole structure ; and should there at any time be a show of weakness on the river face of the concrete, by further abrasions, they will be gradual, giving ample notice of the necessity of repair, without endangering general stability. On the 8th of December last, we received a communication from the President of the Department of Docks, enclosing a memorandum pre- 31 pared by Mr. G. S. Greene, Jr., Engineer-in-Chief of the Department, suggestive of a request for fuller expression of our opinion as to the " system employed in said constructions ; " which suggestion was approved by the Commissioners. Memorandum for President Wales. " Understanding that it is no part of the duty of the Board of Engi- " neers at present examining the bulkhead wall to express their " opinion as to the system or principle employed in its construction, 1 " beg leave to suggest that it would be well to request said Board to " report and express definitely their opinion in regard to the system " employed ; because, though from their report in regard to present " condition and advice as to what shall be done in the future, their " opinion as to the system may be inferred, it would be much better for " this Department to have a decided and definite expression of their " opinion. " In case they report the wall faulty, this expression of opinion would " decide whether it is so by reason of the system, or of bad work under " a good system, and it would also prevent different persons making different inferences from their report in regard to this point. " Respectfully submitted, (Signed) " G. S. GREENE, Jr. ' ' Engineer- in-Ch ief. [Jn Answer.] Throughout our report will be found full details of the defects of the structures under examination, and remarks on what we con- sider the causes of such defects, and how they might probably be obviated. But we suppose Mr. Greene intended his request for our opinion as to the system of constructing concrete mass in situ beneath the surface of water. We cannot condemn a system of which many successful examples are reported, with which we are conversant, nor, under certain circumstances and necessities, should we hesitate to adopt it ; but these do not obtain in the construction of these bulk- heads ; and we should recommend that all exterior faces here should be constructed in blocks and deposited on the pile foundations as hereto- fore described in our modification of the present structures. (Signed) JOHN NEWTON, Q. A. GILLMORE, WM. E. WORTHEN. 32 EXAMINATIONS OF THE CONCRETE EN MASSE OF THE CANAL STREET SECTION. AS MADE BY DIVER T. W. CON KLIN. UNDER DIRECTION OF JOHN NEWTON. Panel No. 19. Partly under and partly north of pier. Shutter removed to depth of 4 feet 6 inches only below offset. Seam, 2 feet below offset, running straight across panel, iy 2 inches wide, too soft to furnish samples. Probed with steel rod }( inch square, gave depths of 12 inches, 9 inches, and 19 inches at the extreme and middle points. By tapping the rod with a hammer, a depth of 25 inches in the seam was reached. A hard blow with hammer could not be made on account of the bending and springing of the rod. Drove in a steel chisel everywhere its whole length of 8 inches with great ease and quickness by tapping with hammer. Samples from top edge of seam. No. 1 from face of wall, top of drowned cement and soft bottom, more sand and better set. No. 2, face of wall, soft with little sand. No. 3, soft and harder set in equal proportions. Samples from bottom edge of seam. No. 4, separate layers of cement and sand without set. No. 5, mostly cement, little sand, sott. No. 6, separate layers of cement and sand without set. Sample No. 7, one foot below seam, hard. Panel No. 12. South of preceding with 6 panels between; under pier. Wall exposed, by removal of shutters, only to a depth of 3 feet below offset. Seam, 18 inches and 24 inches below offset, 4 inches wide. Penetrated by steel rod 6 inches, 13^ inches, and 13 inches at extreme and middle points. Penetration, by tapping with hammer. 17 inches. Seam was soft. Two samples from face well set. Surface of wall hard, and could not get the steel rod in. Would have to drill it with the chisel. Panel No. 11. South of. and contiguous to. preceding ; under pier. Six feet of this panel measured below offset, exposed to inspection. Seam, 2 feet below offset and 4 inches wide. Penetrations, with steel rod, qy 2 , $ l A< anc l 4 inches at extreme and middle points. Hole in north side of panel, 6 inches in diameter and 16 inches deep. Pene- tration of rod by hammer. 21 inches. Sample from seam : cement and sand in separate layers : setting poor. Sample from bottom of hole, very soft cement. From face of wall. Sample : stone with soft cement around it. 33 Sample : cake from around hole ; hard on outside, soft on inside. Sample : thin cake from surface, cement tolerably set. Sample : al- most pure cement and soft. Rod went in 12 inches. Sample : cement, little sand, hard on surface. Sample : stones with soft cement around them. On this panel, whenever the hard, thin, outer crust was removed, the stones could be taken out by hand. Panel No. 10. South of, and contiguous to, preceding ; under pier. Exposed to depth of 9 feet below offset. Seam, 2 feet below offset. Penetrations were made with steel rod along two vertical lines, near the north and south sides, respectively, of the panel. North. South. 10 inches at seam. 1 1 inches at seam. 17 " 4 ft. 6 in. below offset. 39 " 4 ft. 6 in. below offset. 39 " near bottom. 34 " near bottom. Sample from seam : small, of drowned cement. Samples from wall, 21 inches above bottom. Sample : cement, very- dark, tolerably hard, softer on inside. Sample : very dark, muddy, not well set. This panel without hard outside skin, and the face of wall can be removed by hand. The wall is rather harder above the seam. Panel No. 9. South of. and contiguous to, the preceding ; under pier. Panel exposed to depth of 10 feet below offset. Seam, 2 feet below offset. Penetrations of steel rod along two vertical lines at the north and south sides of the panel. North. South. 13 inches at seam. 13 inches at seam. 19^ " half-way down. 24^ " half-way down. 45 " near bottom. 61 " near bottom. Surface of wall soft, and can be removed anywhere by hand. Panel No. 8. South of, and contiguous to, preceding ; under pier. Seam, 2 feet below offset at north, and 20 inches below at south end of panel. At south end the field enlarges into a hole, filled with stones without mortar, 2 feet in diameter and 14 inches deep, but not fully explored. Penetration of steel rod along vertical lines at north and south sides of panel. North. South. \o l /z inches at seam. 14 inches at seam, in hole. 15 " half-way down. 38 " half-way down. 71 " near bottom. 62 " near bottom. Sample, from seam : stones with little mortar, without consistence. Sample, half-way down : stones with soft mortar, having excess of cement. Sample, near bottom : large sample of drowned out, soft cement and muddy. These three samples taken along north vertical line. From south vertical line. Sample, from hole : stones without mortar. Sample, half-way down : stone with mere skin of drowned cement. Sample, from near bottom : of cement and sand, unequally distributed, easily crushed in fingers ; mud on bottom of sample. The outer surface of this panel is soft, and can be easily removed by hand everywhere. Pa?iel No. j. South of, and contiguous to, the preceding. Exposed to depth of 10 feet below offset. Penetrations of steel rod along north and south vertical lines. Seam, 20 inches below offset. Samples along north vertical line. Sample,, from seam : one stone, on the back, soft drowned cement. Sample, half-way down : cement with little or no sand, soft, except a thin skin on outside 1-20 inch thick, which was harder. Sample, from a small section of smooth surface, 2 feet above bottom : outside hard, inside soft. At the bottom, the diver reported concrete soft as in preceding panel. Samples from south vertical line. Sample, from just below seam : a little soft mortar brought up on the chisel, surface is harder ; when penetrated, the diver reports all soft. Sample, about midway down, from a hole : thin, hard film on outside, the rest nearly all cement, easily crushed in fingers. Another sample from hole, tolerably well set for one-and-a-half inches from surface ; the interior soft. This hole was just long enough to get in the hand, but expanded on the interior; it was 17 inches deep. Sample, from bottom : nearly pure cement and soft. This panel is like the preceding, except that the hard, thin, exterior crust has not been so much scaled off. Panel No. 3. South of, and with an interval of. three panels between it and the preceding. This panel south of pier. Exposed to depth of 11 feet below offset. Penetrations of steel rod along vertical line near middle of panel. North. South . 8 inches at seam. 29 •' half-way down. 39 " near bottom. 9 inches at seam. 24 " half-way down. 26^ " near bottom. 33 1 2 6 inches, one foot from top. 2 " four feet from top. ,3 " eight feet from top. Sample, one foot from top : very soft, drowned cement. Sample, 35 four feet from top : stone, with soft cement on back, and piece of mortar, soft on back, all easily crunched in fingers. Sample, about 2 feet above bottom : stone without mortar ; also a separate piece of mortar, nearly all cement, and very soft indeed. Wherever the thin, outer scale was removed, the interior proved to be soft ; if anything - , more so than in the preceding cases. Two Panels, Nos. 27 and 28. North of wharf, and separated from Panel No. 19 by seven panels. Exposed to depth of 6 feet below offset. Next to north pile, surface much broken and can be easily removed. Near north pile and 18 inches below offset the steel rod went in 9 inches ; could not penetrate on account of stones, except at this point, along that vertical line. Sample, stones from face of wall, taken by hand : mortar almost pure sand. Sample : stone with slight trace of drowned cement on back. Along the middle vertical line the rod penetrated 9 inches, about one foot below offset, and nowhere else along this line, on account ol stones. Along south vertical line the rod penetrated 8 inches, about 3 feet below offset, and nowhere else, on account of stones, along this line. Sample : stones with slight traces of drowned soft cement. Sample : four stones with slight trace of mortar. Sample : cement tolerably set on outside, soft on inside. This sample was got out by a chisel, which made a hole 10 inches deep, the concrete being softer as it progressed. The diver reported that he could pick the face all to pieces with his hands. Nearly all the specimens obtained from the panels examined on the 26th and 27th of November were small, because, according to the diver's report, the mortar was so soft or badly set that it was impos- sible to get out larger pieces. [End of first examination of face of wall, Canal Street section.] End of Wall. At west side of cross section, 9 feet to the top of pile. Steel rod, along vertical line, about 4 feet from face of the wall, would not go in over 3 inches because of stones ; no seam found ; surface rough. No shutters had been placed, this end having been supported by piles driven close together. Samples from surface, on vertical line, about 4 feet east of face of wall, and one foot below level of offset : many stones, without adhering mortar ; one with mortar having large excess of sand and tolerably set. Sample, along same line, and about half-way down : many stones 3C> without mortar, also two clusters cemented with mortar having large excess of sand and tolerably set. Sample, along same line, and near bottom : one cluster cemented, excess of sand. Near top of wall, and on same vertical line, a hole was dug with chisel, aided by hammer, to a depth of 14 inches. Sample : two clusters cemented together, from outside of hole, large excess of sand. Sample, from bottom of hole : large number of stones, great deficiency of mortar, large excess of sand generally ; but one specimen showed any cohesive strength. Some specimens also had traces ot soft drowned-out cement. In this sample there was no cementing matter shown upon the large proportion of surfaces. Samples from middle hole on same vertical line, worked 16 inches deep by chisel and occasional use of hammer : mortar on most of the stones, but only in two or three instances all around the stones. In other cases one or more of the surfaces of the stones showed no adhering mortar. The mortar, when it adhered, was generally set, showing excess of sand, but in most instances there was a deposit on the surface of the mortar of a soft material, like drowned cement. Sample, on the whole, one of the best obtained. Bottom hole, in same vertical line, dug 24 inches deep. Two stones, nearly enveloped in mortar, weak from excess of sand. Portion of the sample from the interior of the hole showed stones imperfectly imbedded in mortar containing a large excess of sand, with seams of soft, drowned cement interspersed. The bottom hole caved in, forming an opening, up and down, of 3 feet by 1 foot wide ; a large mass of material fell in. In all these holes the stones were easily removed, and there were no signs of having to stop, as far as they were dug. On eastern half of cross section, a large caving in was found, extending horizontally for the half-width of cross section, vertically about \Yz feet, and was 19 inches deep. This caving was caused, as I am informed, by the shocks of the pile- driver in extending the piling southward, after the piles sustaining the end of the wall had been removed. Pafiel No. 7. Just south of south line of pier prolonged. On south half of panel, 4 feet from top, a seam 4 feet long, 2 inches wide, and 18 inches deep. Sample from surface, 6 feet from top : stones with mortar adhering in two-thirds of the instances ; mortar with large excess of sand. Sample, from bottom of a hole, 19 inches deep : stones showing adhesion of mortar, some of it good, in others excess of sand ; relatively a fair sample of concrete ; a little soft drowned cement. On north half of panel, for 3 feet down, surface of wall was smooth, and could not enter the rod. Surface can be easily removed by using 37 the rod. Below this the surface is gone in many places. Sample of stones from surface showed clearer indications of being imbedded in mortar, and of well set, adhering mortar, than usual. Panel No. ri. Under pier, re-examined. Could not obtain samples from top and middle seams, because too soft. Seams very narrow, about i inch in width. Panel No. 10. Under pier. South of, and contiguous to, pre- ceding. . Re-examined. Sample, from bottom seam : cement soft, in layers with mud or dirt. Sample, from middle seam : cement, most of it soft mush. Sample, from top seam : cement soft, not quite as much so as sample from middle seam. Top seam, 3 inches wide. Sample of mortar, from top edge of this seam : cement with some sand, very tough. Panel No. 9. Under pier. South of, and contiguous to, preceding. Re-examined. Penetration of steel rod, in seams, about the middle of the panel : Bottom seam, about 9 inches wide ; penetration, 42 inches. Middle " " 4 . " 26 Top " " " " " 14 " Top " second trial, " 8 Between bottom and middle seams, in middle of panel, could not enter the rod. Surface full of stones. A hard, firm place. Between middle and top seam, near middle of panel could not get in the rod. Sample from bottom seam ; cement soft, in layers with mud and dirt. Face of bottom seam in places has fallen out to depth of 5 or 6 inches. Place where sample was taken from, 12 inches square. In places as much as 14 or 15 inches wide without stone. Middle seam too soft to get sample from. Sample of stones from upper and lower edges of seam, show little good mortar — generally sand or drowned cement. Sample from top seam, taken from a place 1 foot high : soft cement ; behind the cement were stones easily removed by hand ; most of this sample very soft. Panel No. 8. South of, and contiguous to, preceding. Under pier. Re-examined. Penetrations of steel rod in the seams, about the middle of the panel : Bottom seam, 12 in. wide ; penetration, 23 in. and 38 in. Middle seam, 4 to 6 in. " " 35 in. and 38 in. Top seam, " " 10 in. In middle of panel, rod would not enter between top and middle 38 seams, on account of stones. Stone with cement adhering to it rather hard. In middle of panel, rod would not enter between middle and bottom seams, on account of stones. Sample stones tolerably imbedded in mortar ; excess of cement, and tolerably set. Stones were easily removed by hand. Sample from bottom seam from a place 12 inches square and 10 inches deep : cement in layers, no stone ; dirty, finer portions escaped in bringing up, not set or but slightly. Sample from middle seam, from a space 6 in. wide, 12 in. high, and 6 in. deep : Two stones ; cement in layers ; not as dirty as in bottom seam ; not set, or but slightly. Pa?tel No. 7. South of and contiguous to the preceding — about on a line with south side of pier. Re-examined. Bottom seam, 12 inches wide. Iron rod penetrated 35 inches, all the way across. Middle seam about 6 inches wide ; maximum penetration, 38 inches, minimum, 32 inches. Top seam, penetrations \o]/ 2 inches, 15 inches, and 16 inches. Thin crust from space between top and middle seams. Cement and sand in layers, rather hard. Iron rod went in 1 1 inches. Between middle and bottom seams, rod would not penetrate on account of stones. Sample stones with mortar adhering, having excess of sand, with thin seams of drowned cement interspersed. The samples obtained from the seams, during the re-examination on the 6th and 7th of December, were transferred to a warm room, and kept wrapped in paper to prevent drying. After remaining thus for 8 and 9 days, the papers were opened, the cement was found moist ; but in every case without the least appearance of set. The samples resembled so much mud. The samples were then allowed to dry, and except when dirt had mingled, they were generally very light colored, almost white ; sepa- rating in thin layers which marked successive depositions ; of low specific gravity apparently, the cakes being so light as to float until they absorbed water, which was quickly accomplished. The important facts to be gathered from the foregoing notes of examination, are : 1. Deficiency in hardness and set of the concrete to the extent to which the examinations progressed. The surface of the concrete, in nearly every case, was easily removed by hand. Holes were easily and expeditiously excavated into the mass, to depths varying from 14 to 24 inches, and the concrete did not become harder as the penetration progressed. 2. The inferior condition of the mortar, which, in the large majority of instances, was classed as drowned cement, soft; cement with sand 39 in separate layers, with little or no set ; sand with a trace of cement, easily crumbled in the fingers, etc. ; terms which indicate that the concrete had been subjected effectually to the water-sifting process, by which the constituent parts of the mortar had become separated from each other, to the injury or destruction of cohesive strength. 3. The presence of extensive seams along the face of the concrete mass, principally encountered under the pier of the Pacific Mail Steam- ship Company. Wherever the shutters had been removed to depths of 3, 6 and 10 feet respectively from the offset, one, two, and three seams were found, which indicates that the three seams existed for the whole length of the wall under the pier. The seams undoubtedly correspond to the upper surfaces of successive layers of concrete, and although probed from the outside with a steel rod, as effectually as would be done by a diver, it is by no means certain that the full depths have been obtained, because of the probable presence of stones here and there, and of the irregular and waving form of the beds upon which the seams lie. The lowest seam, corresponding to the top of the first layer of con- crete was, measured on the outside, of a thickness from 9 to about 18 inches. The average penetration was 44 inches, the least being 27,- and the greatest 71 inches. The middle seam, corresponding to the second layer, measured from 1 to 9 inches in depth on the surface of the wall. The average pene- tration was 28 inches ; the least being 1 5. and the greatest 39 inches. The upper seam, corresponding to the third layer, measured on the surface from 1 to 4 inches in depth. The average penetration was 12 inches ; the least being 4, and the greatest 25 inches. Samples of these seams, from excavations made into the wall, to a depth of 12 inches, were tested under favorable conditions for a period of nine days, without the slightest appearance of set. From the middle and top seams much of the material was a mush ; while from the lowest seam, the material, in its wet state, presented the appearance of having been compressed. On drying them, however, all the lump samples turned out the same — that is, very light and porous. When the concrete was green, its weight undoubtedly compressed the seams ; but as the layers began to consolidate and become self- supporting, the materials of the seams relieved in part of pressure, yielded more readily to the dissolving and washing power of the water, and have become very porous or mushy. For a certain distance in from the face, the seams, therefore, give no support to the layers of concrete. I have been informed that the intention of the constructor was to have had the deposits upon the top of each layer cleaned off before 40 the next layer should he placed. His instructions were but partially executed, it is true, but sufficiently so to prevent the seams being found continuous through the width of the wall. For there is no reason, other than that, to account for the non-appearance of a feature which, in the general case, should have been uniform for the same layer of concrete. This consideration opens to view the large extent of these seamy deposits, of which only a fraction have been Left for our inspection, but sufficient to prove that the waste of cement by the water-sifting process was great, and the injury done to the concrete in proportion. 4- Another fact, worthy of record, was the formation of a very thin, hard scale, more or less extensive, upon the outer surface of the mass concrete. This indicates a conservative, rather than destructive, influence of the dock water. However, as the Commissioners have it in their power to discharge the sewer water into the current at the end of the piers, the question ol its effect upon the bulkhead wall loses much, if not all, of its prac- tical importance. Experiments in the Department have been instituted upon the effects of the sewer water upon Portland cement concrete, already with definite results ; and it would seem best to leave the matter there. Mr. B. Latham (Exc. minutes of the Proceedings of the Institution of Civil Engineers, Vol. XXXII. Session 1870-71, Part II.) states: " During the last two years he had found that sewers which had been " constructed for about seventeen or eighteen years, the brickwork of " which was set in various kinds of lime and cement, and in some " cases in a mixture of both, were failing, and many yards of such " sewers had fallen in." This was due to the disappearance from the joints of every particle of cement or lime. He also states that Portland cement was the best material for resisting the chemical action of sewage. It will be observed above that it required seventeen or eighteen years to produce the effect, under exposure to the concentrated effect of the chemical action, in the sewer itself. The Portland cement used was of good quality, slow setting, and weighed about 112 lbs. to the struck bushel. The constituents of this cement are of very different specific gravities, and the particles, which are of several degrees of fineness, vary considerably in weight. The paste of such cement is not unctuous, like that of Rosendale cement and hydraulic limes, and is consequently destitute of the power, possessed by these in a green state, to hold the mortar well together when exposed to the wash consequent, generally, upon lowering in water and depositing. This, which was indeed a prior conclusion, has been proved experimentally. In experiments made with the same bucket that was used for the +1 actual construction of the mass concrete, and under precisely the same conditions, it was noticed repeatedly that, before complete immersion, the water had penetrated through the load of concrete from the bottom to the top, and was flowing through in a continuous stream. At the moment of immersion the surface water tumbled into the bucket with a considerable force — for the bucket was not full and had no top — and added to the wash. The bucket is of wedge shape, lowered into the water with the edge downwards, and has its discharging gate on the side. The consequence is that, instead of depositing its load in mass by one operation, the concrete is compelled to slide out in successive portions through the water and undergo the sifting process. The formation level is a layer of 4-inch rubble, packed or placed between the heads of the foundation piles, which last projects variously, sometimes several feet, above the rubble. The bucket, stopped in its descent by the heads of the piles, must discharge through several additional feet of fall before its contents can reach their bed. Under such circumstances the sand and heavier portions of the cement fall to the bottom and penetrate into the rubble below, while the lighter portions float and form, by subsequent deposit, the lowest seam, which was uniformly found to be the thickest of the three. The concrete between the pile-heads, deprived thus of mortar, is generally a mere mass of rubble, not cemented at all, or but imperfectly. The pile-heads have not been sawed off, except, perhaps, those of the front and back rows. In addition to sticking up irregularly, a number are broomed, or split, and, therefore, incapable of sustaining a full load. It appears to have been the idea that the concrete packed between them would grasp and bind the heads, as by a ring, and so compensate for their weakness. But when the rubble settles, as it must, the crumbling concrete between the pile-heads will fall too, and leave these without the expected support. The lower, or foundation, layer of concrete is the worst of the three or four layers, because the concrete has to fall through a greater depth after discharge from the bucket, and the heavier parts of the mortar are lost in the interstices of the rubble. It is also clear that the pile- heads should have been cut to a level, and an impervious bed or plat- form provided to receive the first layer. From the mode of depositing the concrete, as likewise from the peculiarities of this slow-setting cement, a considerable wash has also taken place in the layers above, although not as much as in the lowest one. Owing to the want of unctuosity of the cement and its slow setting, the disintegration of the mortar continues some time after deposit, and those portions, as the sides of the wall exposed to the water, show this 42 action more than the interior mass, which has been better protected. It is also evident that the mode adopted of depositing the concrete in long successive layers was injurious, because of the large surfaces unnecessarily exposed to the action of the water. It would have given better results had the full height of the mass concrete been deposited in sections of limited length, such as to have insured their completion by a continuous operation. It is not intended to assert that there is no concrete of fair quality contained in this wall ; but, from the causes mentioned, the results are so uncertain that serious defects have appeared in places where the wall was required to be of unimpaired strength. As a monolith it is imperfect, if not essentially a failure ; and besides the defects already cited, attention should be called to the fact that the front row of piles intended to have good bearing, particularly against the thrust of the earth backing, can give no support to the wall, because the angle or toe of the wall, against which the piles abut, has fallen away, or is too weak to answer the purpose. At one period Portland cement was used with much misgiving, because of the ignorance and selfishness of manufacturers, and the want of systematic experiments calculated to explore the subject fully or to classify the properties of the several varieties. The lengthened course of experiments of Mr. fohn Grant were conclusive in their effects to remove prejudice and to demonstrate the excellence of the heavier and slow-setting brands. Mr. Henrv Reid states, in his work on the manufacture of Portland cement, that " much of the clamor against heavy cement is caused " by its slowness in setting, and doubtless great waste and loss is " occasioned by many using this quality of cement for purposes to " which it is unsuited." (Edition of 1868). But since that period the thorough endorsement of this quality by experiments and actual con- struction, has rather changed the risk to the other side, and induced waste and loss by its application to purpose for which it is not suited. The instances given of the application of Portland cement in hydraulic constructions are often vague and inconsequent in the details. One instance is taken from the work just referred to of the con- struction of the foundations, inside of cylinders, of a bridge across the Thames, at Windsor. The cylinders were sunk through the gravel without pumping, and, of course, were full of water. Through that water the concrete was passed, and it set well and hard in eight or ten days. The proportions were one of cement to nine of ballast, increased afterwards to one to six. On pumping out they tested the concrete by drilling nearly three feet, and no amount of drilling, consistent with reason, could make any further impression. They were so encouraged 43 by this essay that they applied the same process in cylinders, through depths of water from 50 to 70 feet. At first sight all this sounds well, but when the question comes how, by penetrating three feet into the top surface of the concrete, it is possible to certify concerning the quality of the concrete at greater depths, the fallacy of the reasoning becomes apparent. Had such mode of investigation been relied upon, we should probably have found no defect worth mentioning in the Canal or King Streets sections. If the foundation upon which the cylinders rested was gravel, an inves- tigation there would show that the bottom courses had lost their cementing portions, which had fallen into the gravel. It made very little difference, in fact, to the security of the pier, whether the con- crete was good or bad at all depths, because it was confined in cylin- ders ; but the inference, that the concrete was good because the piers stand, is too gratuitous to need refuting. The effect of such loose modes of presenting a subject, is simply to mislead engineers, who are not experts in concretes, by the sanction of high authorities, into the commission of grave errors. Mr. Kinipple, on the other hand, quoting from the same book, states that he had ascertained that in only one inch of quiet water, concrete of Portland cement, made in the propor- tions of one to three, was endangered by the working out of the silicate, or the best of the cement, from the ballast ; and he furnishes an instance in point from his own experience. He says further, that, to avoid this for the future, he had resolved that all Portland cement concrete should be mixed on the surface and allowed to set for several hours, the length of time for setting to be in proportion to the quantity of the cement used ; and, when set, to be used in a crumbled condition. By experiments he found that he was able to retain nearly the whole of the cement without any loss as to strength. The two examples cited show conspicuously the differences of state- ment between an engineer who knew something of the subject and was possessed of a logical mind, and another who did not enjoy such advantages. The practice of the Imperial Austrian engineers and of the Italians, in the use of concrete made with puzzolana and fat lime, is worthy of mention, as it proceeds on the principle laid down by Mr. Kinipple. The mixture is made two or three days before being deposited in the water, for fear, if used in a green state, the lime would be separated by the water from the other ingredients. After the interval cited, the mass is shoveled or dumped into the water without further precaution, and makes excellent concrete because there is no separation of the con- stituents of the mortar. We have seen that Rosendale cement and hydraulic limes which possess unctuous properties, can be relied upon to hold together in 44 water until setting takes place, and Mr. Kinipple recommends for Port- land cement of the heavier varieties, which do not possess that property, to allow a partial setting before deposit in water. This would be worthy of trial by the Commissioners in a series of experiments calcu- lated to test it severely. The misfortune of the mass concrete, deposited at Canal and King Streets, has been, that it was open to rigid investigation and test ; while the concrete locked up in cylinders at a depth of 70 feet, of which such a vague and flourishing statement has been published, is, fortunately for the eminent engineers concerned, put away beyond the reach of an investigating committee. For the rest, if the walls at King and Canal Streets be regarded as simple experiments, their value in saving future loss by forcing builders back to the true principles of using concrete, will more than compensate, even to the Department, for the loss and delay incurred. The defect of weakness found in the toe of the wall, by which the front row of piles have lost their bearing, and transferred that bearing to the second row, has in reality diminished the stability of the wall one quarter. An error, in my opinion, was committed in driving close together the front and back row of piles. By this means the wall is really prolonged to the bottom of the piles, without increasing its weight or resistance to overthrow' one particle ; while, on the other, the rows of piles and the walls supported on them, have to endure the preponderance of the thrust of the filling behind communicated through the mud now in place. This thrust is as easily calculated as any other against a dock wall, and by the same rules ; and, it seems to met, should be me by as definite a contrivance to resist the pressure, as would be done in ordinary cases. The system of throwing in rip-rap stone in front of the wall and of driving piles behind the wall, to resist and break up the thrusts, seems to me very uncertain and unreliable ; since these cannot be based upon definite calculation, and it is impossible to tell whether sufficient has been done or not. The yielding of the wall, which it should have been the purpose to prevent, would seem to be the only monitor in such cases. These matters will be made the subject of remark in joint report, and nothing more need be said in this place. Respectfully submitted, JOHN NEWTON. 45 King Street Quay Wall. Notes of an inspection made by Q. A. Gilbnore, with Marine Diver John Burt, between October 13th and October 26, 1875. The spaces between the square caisson piles, which stood 8 feet apart between centres, are termed panels in the following notes. They are numbered from north to south, in both front and rear. Where the shutters, or plank-panels, between the piles had not been removed, a note to that effect is inserted, as no inspection could be made in such cases. A plan, cross section, and elevation of the wall and foundation is shown on Plate accompanying the joint report. In the first, second and third panels (front), (the shutters are still in ). Not examined. Fourth panel (front), concrete offset at base of wall mostly gone, and can be easily picked off with the hand where it remains. Some of the 4-inch rubble-stones were brought up from under the concrete about 1 foot inside the face of same. They were easily taken out by hand. Rubble at this point sustains none of the weight of the wall. A pile under the wall was felt where the rubble had settled away from concrete. It is not certain whether this pile belonged to first or second row from face of wall, probably the first. Nearly half a bucketful of concrete stone was picked off and brought up from face of wall, 5 to 6 feet above the bottom. Face of concrete, over entire panel, rough and uneven, only a very small portion of it being the original face. Depressions in face, 5 inches, 6 inches, 7 inches and more in depth, and easily enlarged with the fingers. Offset measurements, horizontally from the north panel pile, showed that at the bottom the concrete had fallen away from face to a depth of 19 inches, and half-way (or 6 feet) up, to a depth of 13 inches. (See Fig. 1, Plate I.) Fifth panel (front), concrete offset mostly gone as in fourth panel, but not quite so badly. Of the original face of concrete, only about 4 or 5 superficial feet remain, the rest having crumbled off, but apparently the loss is not so great in depth as in fourth panel. Along the toe of the wall, the con- crete stone from the face above is piled a foot high. Horizontal offsets show that, at the north panel pile, the concrete has 46 fallen off the face of wall to a depth of 1 1 inches, making a cavity about 5 inches deep under lower granite block, 6*4 inches deep at \]4. feet below granite, and iyv 2 inches deep near bottom of concrete. These measurements are in the deepest holes, but in no place opposite pile is there any of the original face of concrete left. These measurements all assume the concrete berm to be 6 inches wide; but in aligning the lowercourse of granite, the berm varied in width from 5 to 7 inches. A corresponding variation ensues in the offset measurements. In ounding from the top of wall with a heavy boat-hook, the soft upper part of offset could be distinctly felt, and the hook could be hooked under the lower stone for nearly the entire width of panel. After press- ing the iron point down through the soft concrete on the berm, it struck firm concrete below (6 inches. 7 inches, 9 inches, 10 inches, or 12 below). (See Fig. 2, Plate I.) Sixth panel (front), offset not so much gone as in fourth and fifth panels, but only one patch about 3 feet by 2 feet of the entire panel face shows original surface of concrete. Pile of concrete stone and sand at toe of wall 1 foot to 2 feet deep above rip-rap. Concrete face not so uneven as fourth and fifth panels. Measure- ments at north panel pile show hole in concrete about 6 feet below offset, 16 to 17 inches deep, and another, near bottom, Z l / Z inches deep. At offset, no holes exist under the stone ; offset averages about 3 inches to 4 inches in width, and is soft on top for some inches down, as determined by boat-hook point from above. The offset would not show a 6-inch berm below at any point, the edge of it being replaced by a batten for a straight-edge, used for leveling the top of concrete mass before laying the stone. (See sketch.) Seventh panel (front ), offset very good and quite firm, after getting through a few inches of soft material. Face of concrete fallen off 1% inches deep, 2 feet below offset. Not off at all, 4 feet below offset. Off \.y z inches deep, 6 feet below offset. Not off at all, 8 feet below offset. Not off at all. 10 feet below offset. « Face of concrete very good, all over the panel but some holes in wall, not large or deep, and none deeper than 4 , 4 inches. Debris, at bottom of wall, about 1 foot 8 inches deep above rip-rap. This could not have come from the crumbling on face of the wall, but is probably mud. Eighth panel (frontj.face of concrete better than any preceding panels. Diver selected a smooth surface (original surface), and dug a hole in with a steel drill. Hole about 6 inches deep by 6 inches broad. Took him about four minutes. Brought up a handful of the concrete 47 stone from hole. The drill was of 8-inch octagon steel, 21 inches long, edge H inches wide, and very dull. At the north panel pile, there is a hole in face of wall about 2 feet wide and 3 feet high, by 6 inches deep horizontally. Top of hole, 1 foot below offset. Other holes on this face are small, but along the bottom of concrete the face at toe of wall has crumbled off to a depth (in face of wall) of 4 inches and height above toe of wall of io inches to 12 inches. (See Fig. 3, plate I.) Ninth panel (front), offset in tolerably fair state. At 2 feet below, offset hole 5 inches long. " 4 " " " face not off at all. " 6 " " " " '« " " " 8 " " " hole 8 inches deep. " 10 " " " face not off at all. Face of concrete generally rather smooth and not broken off, but apparently not so hard as previous panels. In digging into it with a drill, however, it was found to be quite as hard. About 4 feet above bottom of wall a pile-head is exposed on face of concrete. Diver dug a hole in original face of concrete with a steel drill, 5 feet below offset, in 9 minutes. Hole 5 inches deep and 5 inches broad. Firmest place selected for this purpose. A bucketful of concrete stone was picked from face of concrete by the fingers, about 1 }4 feet above bottom. (See Fig. 4, Plate I.) Tenth panel (front,) offset not so bad, but some of the edge knocked off. Two-thirds of face of panel smooth. Rubbish at foot of wall 2 feet high. Dug down through rubbish to foot of wall, and then dug into wall with a hoe about 4 inches. Sound concrete here, better than in any previous panel. At 18 inches below offset, concrete at north pile off to depth of inches, and to a width of 3 feet, and a vertical height of 1 foot. From that point down to toe of wall, no concrete off. At middle of panel little or no concrete off. straight-edge fitting pretty close up and down. (See Fig 5, Plate I.) Eleventh panel (shutter still in place). Twelfth panel (front), face of concrete over entire panel, in better condition than any previously examined. Offset pretty good. At north panel pile, concrete off to a depth of 4 inches about \]/ 2 feet below offset, extending across to south panel pile. This is probably the soft concrete formed under the batten at top of concrete to receive straight-edge. At 9 feet below offset, concrete soft and off a little ; dug a hole 8 feet below offset, 5 inches deep and 5 inches broad with drill in 48 seven-and-a-half minutes ; concrete harder than in holes previously dug. Could not pick out concrete stone with fingers. Concrete stone, sand and mud, about 2 feet deep, over rip-rap, at toe of wall. Dug through this debris and got at toe of wall at south panel pile, and dug into face of wall with the hoe about 9 inches, for a height above bottom of 2 feet, and a width of about 1% feet. Found concrete very poor, and could crumble off concrete stone easily with fingers. Went down to broken stone foundation, and could put hand under the wall. Thirteenth panel (shutter still in place). Offset sounded with pick from above, felt quite firm, after penetrating a few inches of soft material. Fourteenth pa?iel (shutter still in place). Fifteenth panel (front), about half ot original surface of concrete remains ; other half off. Offset 1 1 inches wide : 2 feet, be 4 " 6 " ow offset, lyi, in. concrete off. " o 14 " 3/2 As determined by straight- edge. Dug a hole at toe of wall, 12 inches deep in face of wall, 18 inches high, and 20 inches wide. Found a pile about two inches in from face of wall. Concrete in hole quite soft ; could pick off concrete stone easily with fingers. Concrete around head of pile pretty firm. Dug hole with steel drill at south panel pile 6 feet below offset, 9 inches deep, and 7 inches broad, in n minutes. Concrete not so soft as some heretofore examined. The hole was located on a smooth con- crete surface. (See Fig. 6, Plate I.) Sixteenth panel (front), covered by temporary coffer-dam, and not examined. Seventeenth panel (front), offset very good, and face of concrete same. Good face on about two-thirds of panel — in bad order at the bottom ; 3 piles of outer row exposed ; could reach nearly around one of them. Near north side of panel, measured in horizontal from straight-edge. Offset 10 inches wide. 2 feet down, 3 inches concrete off. 4 " " o " 49 6 feet down, o inches concrete off. 8 " •« X " io " " 6j4 " Below this the toe of wall is broken under badly. Put in a rod twenty-three inches horizontally into wall where concrete was off. Near the south panel pile the offset is 1 1 inches wide. 2 feet down, 1 1 inches concrete off. 4 «« « 9 y 2 « 6 " " 2 " 8 <« « 2^ " io " " 9^ " Below this the diver dug out a hole in toe of wall, and could easily pick off concrete stone with fingers. (See Figs. 7 and 8, Plate I.) At south side of this panel could run a thin stick under lower course of granite 4^ inches. Eighteenth panel (front), offset very good, but the cavity found under the lower course of granite at north panel pile extended south- wardly to south panel pile. At south pile it is 2 inches deep, 2 feet north 4 inches deep, 4 feet north 9^ inches deep, 6 feet north 19 inches deep, and at the north panel pile stick went in under stone 22^ inches. Cavity 1% inches wide vertically at north panel pile ; not so wide else- where. About half the face of the concrete is smooth ; the rest pretty rough. Concrete at bottom of panel badly broken off, and easily broken off with fingers. At bottom found one pile-head exposed for half its thick- ness. Wherever concrete is found on top of pile-head, it appears to be harder than elsewhere, having been more compressed. Horizontal measurements were taken at north pile where offset is 12 inches wide. 2 feet down, 6 inches concrete gone, 4 " o 6 o 8 " "4 " 10 " " 3 At south panel pile or near it, the offset is 12 inches wide. 2 feet down, 11 inches concrete off. 4 " 6 50 At toe of wall at south panel pile, hole in wall 22 inches deep, hori- zontally. Dug hole 6 feet below offset in middle of panel in 7 minutes, 6 inches deep and seven inches wide. (See Figs. 9 and 10, Plate I.) Nineteenth panel (shutter yet in). It will be observed that no bad seams were reported by the diver during the examination above described. Another examination ot the front of the wall was made about seven weeks later, on the 9th and 10th of December, with the assistance of Diver Conklin. who had been em- ployed in finishing the inspection of the Canal Street wall. The object of this second examination was to check the previous one, as well as to ascertain whether any extensive seams of laitance and river filth, such as characterized the Canal Street wall, were to be found in the King Street structure. The notes of this second inspection are given below. Second Examination of the front of the King Street Wall, by Q. A. Gillmore, assisted by Diver T. W. Conklin. Fourth panel (front), examined the wall up to down the middle of panel, with a steel probe, and could find no seams. Face gone all over the panel. Two foundation piles exposed near the north panel pile. Could not push the probe in anywhere in this panel. Fifth panel (front), could .find no seams with the steel probe. Nearly the whole face of this panel is rough and crumbled off, and con- crete could be crumbled off by rubbing it with the hand. No meas- urements of depth were taken. Sixth panel (front), same record as the fifth. Seventh panel (front), same record as the fifth. Eighth panel (front), no seams. The face is smooth down 8 feet from top. Below that the toe of wall is caved under several inches, all the way across panel. There is no hard scale on the face of the con- crete, like that found on the Canal Street wall. Ninth panel (front), found no seams with the steel probe. Four feet down fr^.m top, soft but smooth. Below that scaled off considerably in places, but no measurements of depth taken. Tenth panel (front), on north side, 3 feet down, found a place 4 to 6 inches wide, and 2 ]/ 2 feet long, where the probe went in from 6 to 9 inches. Rest of panel scaled off some, but no measurements taken. Twelfth panel (front), at 18 inches below offset, in the middle of the panel, the probe was pushed in by hand 9 inches into the original face of the concrete. Face of entire panel pretty good generally. There is a 51 seam, about 4 feet clown from the top, about the middle of the panel, r inch wide and 2 feet long, into which the probe went 17 inches. Fifteenth panel (front), upper half pretty good and very little of face off. Lower half very soft. Can run probe in 6, 9 and 12 inches in many places in lower half. No seams were found. Could easily pick off concrete stone with the fingers. Seventeenth panel (front), face pretty good on the upper half, but badly broken under at the bottom, near the north side of panel. Run the probe into cavity 4 feet in one place. The height of break reaches to about 6 inches above the heads of outer row of piles. Could rub off concrete stones with hand easily. Could not run the probe into con- crete anywhere ; it was always stopped by the stones. No seams were found. Eighteenth panel (front), could pick off the concrete stones easily. It falls off the face of wall by rubbing the hand over it. Probe cannot be pushed in on account of concrete stones. Bottom of panel badly- caved under, all across the panel ; in one place can reach under the full length of the arm. Rear of King Street Wall. Examined by Q. A. Gil hn ore with Diver John Burt, October 13th to 26th, 1875. Nineteenth panel (shutter not yet up). Eighteenth panel (rear), face of concrete only 9 feet high above rip- rap, owing to sloping offset at top. For 7 feet down from top concrete is smooth, and shows original face. Below that broke down and under badly for entire width of panel. Four piles of outer row exposed, and can be touched with the hands. Can reach under heel of wall 18 to 20 inches for entire width of panel. This cavity is about 2 feet high. (See Fig. 19, Plate I.) Seventeenth panel (rear), upper part of panel, for 7 feet down, pretty good and smooth. The lower two feet of face caved off, for entire width of panel, 10 inches deep at north side, and 6 inches at south, horizontally. Felt 2 piles at north side. Made hole in concrete with drill, about 5 feet down, on north side of panel, hole 9 inches deep and 6 inches broad, in four minutes ; concrete very soft and easily dug out. (See Fig. 18, Plate I.) Sixteenth panel (rear), face of concrete very soft and not quite as smooth as the two previously examined. Smoothest part reaches from 52 the top down 7 feet, or 2 feet above bottom. The lower 2 feet of face caved off. At north side of panel cavity 8 inches deep, horizontally, growing deeper toward south side, where it is 18 inches deep. At one point, at south side, run a stick 2 feet 1 1 inches under wall. Diver broke a fragment from top edge of concrete face 6 inches to 8 inches, by 3 inches to 6 inches, by 5 inches to 6 inches, composed entirely of sand, cement and laitance. Probable subsided washings of concrete. Concrete quite as soft as in seventeenth panel. (See Fig. 17, Plate I.) Fifteenth panel (rear), October 25th. Good face down to 7 feet from top. At that point a long cavity occurs, 1 foot wide vertically, reach- ing entirely across the panel, from 6 inches to 10 inches deep. Bottom of wall better than previously found on rear face. Dug a hole near north side of panel, 4^ feet down from offset, in 3 minutes with drill, 7>£ inches deep (conical), 8 inches diameter. (See Fig. 16, Plate I.) Fourteenth panel (rear). October 25th. Face good for 7%. to 8 feet down from offset. There a break occurs clear across heel of panel, 8 inches deep, horizontally, at north side of panel, and 1 foot deep at south side, from 1 foot to \y 2 feet in width, vertically. Found 3 piles exposed ; of 2 of them could feel around one-third of their face, and of 1, two-thirds around. At the break, named above, concrete soft. About 4 feet down at north side, dug conical hole in face of concrete with drill, 5 inches deep and 5 inches in diameter, in 9 minutes. Concrete much harder than at any other place yet examined in rear. (See Fig. 15, Plate I.) Thirteenth panel (rear), October 25th. Face pretty good down 73^ feet from offset. There a break occurs ; at south end merely rough ; at north end, 15 inches deep horizontally, and 1 foot high. In the middle of panel, about 4 feet down, dug a hole with a drill, 13 inches deep and 10 inches in diameter, in 6 minutes. Twelfth panel (rear), October 25th. Face generally good. At south pile, t 8 inches below^ top, 8 inches depth ot concrete gone, 18 inches wide, and running off to nothing at a distance of 2 feet. At north pile, concrete gone all the way down 3 inches or 4 inches deep, and 2^ feet wide, horizontally. At heel of wall there is a pile of mud about 2 feet high. Dug into the mud, and at a depth of 8 feet down, found a break in base of wall, 5 inches deep at south side. Dug hole in face about 4 feet from top, with drill near north side, 12 inches deep, 12 inches diameter in 5 minutes. Concrete quite soft. Eleventh panel (rear), October 25th. Face generally rough, the only 53 smooth part being above a line drawn from the top at south pile, to a point 4 feet down at north pile ; about 2j4 feet depth of mud at base. (Continued October 26th.) Dug conical hole in face with drill, 3 y 2 feet down, near the north side. 5 inches deep, 6 inches diameter, in 9 minutes. Concrete pretty hard, relatively. Tenth panel (rear), October 26th. Face good above a line drawn from a point 4 feet down at south pile, to a point 8 feet down at north pile, the line being crooked. (See sketch.) Below this smooth face a break is found at south pile, where the con- crete is off to a depth of 12 inches, extending from smooth face to bot- tom, and in breadth extending over to north pile. (See shaded part of sketch.) Dug hole with drill near north side, 4 feet down, 5 inches deep, 5 inches diameter, in 5 minutes; concrete soft. (See Fig. 14, Plate I.) Ninth panel (rear), October 26th. Face good down to 8 feet from offset, where there is a break extending entirely across panel, 8 inches deep at south side, merely rough in middle, and 4 inches deep at north side, and 1 foot high all along from pile to pile. At north pile, 4 feet from top, a piece is out, making a hole 6 inches deep, 1 foot wide and iX ^ ett high . Dug conical hole in face, about 4 feet down, near north side, 6 inches deep, and 7 inches diameter, in 7 minutes. (See Fig. 13, Plate I.) Eighth panel (rear), October 26th. Face of concrete pretty good all the way down. The hole, mentioned on the north side of ninth panel, extends through into the eighth, and is about 4 inches deep horizon- tally, and 1 foot high and 1 loot broad. Could find no break at foot of wall ; but the concrete is soft, and con- crete stone easily pulled out with the fingers. About 2 feet depth of mud at base of wall ; could easily thrust the arm through it to base of wall. Dug a hole, 3 feet down at north side 6^ inches deep, about 7 inches broad, in 6 minutes , hole nearly round on the face. Could easily pick out concrete stone with the fingers. Seventh panel (rear), October 26th. Face pretty gcod down to 7 feet ; there it is rough at the south pile. In middle 4 inches in depth gone ; north side smooth. About 8 feet down in middle of panel (for one- third its width) gone to depth horizontally of 8 inches ; 18 inches depth of mud at base. At south pile on top at offset, a piece gone 2 l / z feet long, lengthwise of wall, 18 inches wide and 10 inches thick, of wedge shape. (See shaded area at x.) Probably a piece broken off as a sample, or accidentally in removing shutters. 54 Dug a hole y/ 2 feet down, near north side, inches deep, 6 inches diameter, in 8 minutes. (See Fig. 12, Plate I.) Sixth panel (rear), October 26th. Face pretty good all over. About 3 feet down, at south pile, concrete gone 6 inches deep, 10 inches wide and 18 inches in length. From 12 to 18 inches depth of mud at base of wall. Felt well along the heel of wall, and found it in good order. Dug hole in face 2> l A f eet down, near north side, 10 inches deep, and 10 inches in diameter, in 6 minutes. Quite soft. Fifth panel (rear), October 26th. Face generally smooth. Small pieces chipped off upper edge at offset. At a point y/ 2 feet down, con- crete gone at south side, 6 inches deep, 18 inches in lergth, and 12 inches in width. Remainder of panel good to bottom ; the best that had been examined in the rear. About 10 inches depth of mud at heel of wall. Dug hole 4 feet down, on north side of panel, 7 inches deep and 7 inches in diameter, in 5 minutes. (See Fig. 11, Plate I.) Fourth panel (rear), October 26th. Face good. About 8 feet down, found an opening or horizontal crack 18 inches long, about middle of panel. Could just pass the hand in. Found the concrete soft. Opened a place 1 foot square and 4 or 5 inches deep with his hand. Dug hole 4 feet down, near north side, 6 inches deep, 9 inches diameter, in 7 minutes. Not so soft as in some other places. Third panel (rear), October 26th. Good face for two-thirds of sur- face. Roughened at each pile. Corners gone where bottom was on pile. About 7 '4 feet down in middle, found horizontal crack, 3 feet long. Could pass hand in 5 inches and pull out stone. Dug a hole in face 4 feet down, near north side, 7 inches deep, 7 inches diameter, in 3 minutes. Dug a hole 8 feet down near south side, 6 inches deep, 7 inches across, in 3 minutes. Concrete about same hardness in both places. Second panel (rear), October 26th. Face rough on upper part down to 7 feet. Roughness apparently not over 4 inches or 5 inches deep. Bottom apparently smooth, as felt through about 2 feet of mud. Dug hole 3 feet down near north side, 1 1 inches deep and 8 inches across, in 3 minutes. About 8 feet down, near south side, dug a hole, 5 inches deep and 7 inches across, in 4 minutes. Apparently harder than in the hole above. First panel (rear). (Shutter yet in.) Quay Wall Foot of Canal Street, North River. Inspected by Q. A. Gillmore, with Diver John Burt. The panels are numbered from south to north in front and rear. (See Plate of the joint report.) Rear Panel No. 20. New work laid in early part of July, 1875. 55 White's cement in rear, Knight, Bevans & Sturges' cement and White's in centre and front. Upper 6 feet rough and loose. General face pretty good. 3 feet down a seam about 1 inch to \ V Z inches wide, run- ning across face horizontally. In some places a -}^-inch rod goes in 2 feet 6 inches on north end ; south end not so deep. Good then to 8 feet down. Another seam then 1% inches to 2 inches wide ; ^-inch rod can be run in 3 feet in some places. 1 foot further down (at bot- tom) hole produced by board, good, nicely rounded off, solid ; good undeineath. In north side of same panel, 4 feet down, dug a hole 5 inches deep, about 6 inches broad, in 5 minutes. Concrete pretty soft. Pulled out some stone with fingers as soon as hole was started. More like King Street Wall, except the face, which is harder and smoother. (See Fig. 1, Plate II.) Rear Panel No. 24. About 6 inches down from the top a piece of scantling lying on wall, leaving the top rough and broken. About 1 foot below the top, there is a seam running underneath the scantling horizontally, 2 to 3 inches in width ; rod goes in whole length of 3 feet. 3 feet down another horizontal seam 1 \/ 2 inches wide ; bar went in 5 inches. 7 feet down from top a small seam scant 1 inch in width ; rod went in about 3 inches. General face pretty good. l\ 1 / 2 feet down on north side drilled hole, 5 inches deep and 7 inches in diameter, in 6 minutes. Not so soft as in previous panel. Picked stone out with fingers. Concrete pretty good at bottom. Whole height examined, %)/ z feet. (Fig. 2, Plate II.) Rear Panel No. 13. Partially examined by Mr. Worthen. Begun where his work stopped the day before. Upper edge slightly broken. About 2 feet down a horizontal seam across face of panel, 2 inches wide and 4 inches deep. 5 feet down, good. Then a break takes place, about 5 inches deep, for 2V 2 feet down. Remainder rough, but full. Nothing lost at heel. Drilled hole about 3 feet down in smooth part, 4^ inches deep and 4 inch diameter, in 6 minutes. This was on north side of panel. Soft- est concrete yet tried as shown by drilling. (Fig. 3, Plate II.) Rear Panel No. 14. Upper edge good. \)/ 2 feet down a horizon- tal seam across the face, width 1 inch, depth 4 inches. 5 feet down from top on south side, a break occurs extending horizontally over % of panel, and vertically 2 feet. Deepest part of break, 4 inches. On north side, 5 feet down, a seam occurs 1 y 2 inches wide and 8 inches deep. Remainder of panel not smooth but good for 8 feet down ; cannot get down the other foot owing to rip-rap. (See Fig. 4, Plate II.) Rear Panel No. 1 5. First one foot down, pretty good, then a seam, ^ inch wide ; rod went in 3 to 4 inches. Then good to 4^ feet from 50 top, where another seam occurs, almost horizontal, I ]/ z inches wide and 6 inches deep. feet down there is a break, depth of break about 4 inches, extending about 9 inches along face of panel. Rough, but pretty good below this. General character of face good. Got down y i / 2 feet on this panel. Drilled hole 24 feet down, 2}4 inches deep, about 3 inches diameter, in 6 minutes. Very hard. (See Fig. 5, Plate II.) Rear Pa7iel No. 16. Diver down 20 minutes. 2 feet down there is a small horizontal seam 1 inch wide, about 5 inches deep. Down to 7 feet from top, good ; then another seam goes across the face \]4 inches wide and finches deep. Underneath this seam, the north side of panel is broken down, and 4 piles exposed, the north pile being 18 inches from face of wall, and the others gradually coming nearer to face. General character of the face good. (Fig. 6, Plate II.) Rear Panel No. 17. Upper part not very good for 1 foot down, then a seam, running across horizontally, 1 inch wide and 4 inches deep. 3 feet from top for 2 feet down, wall rough but pretty good. From that to 7 feet down good, then broken away 1 foot deep at north end and 6 inches at south end. Felt one pile at south end, part of it in concrete. Smooth head, can put hand partly round. Drilled hole in rough part of wall at north end of panel, about y/ 2 feet from top, in 5 minutes, 9 inches deep and 7 inches in diameter. Very soft. Could pull out stone, due perhaps to seam running across. ( Fig. 11, Plate II.) Rear Panel No. 18. Upper part little better than previous panel. One foot down a seam, 1 inch wide and 4 inches deep. 3 feet down another seam, 1 y z inches wide and 6 inches deep. Wall pretty good down to seven feet, then broken in badly. Can reach in 3 feet at bot- tom (or 9 feet down from top.) Felt 4 piles ; middle one flush, with original concrete face ; south pile further in, about 2 inches. General character of face pretty good above this break. (See Fig 10, Plate II.) Rear Pane! No. 19. Upper part not very good for 1 foot down. Then comes a seam 1 inch wide and 5 inches deep. Then pretty good below, for a distance of iV z feet from top. Then another seam 3 inches wide and 2 feet deep at nonh end, and 1 foot deep at south end. Below that, down to 7 feet from top, wall pretty good, but rough. Then a deep break cccurs. Could find 2 piles pretty well in. Can reach in 3 feet with bar at the bottom. (See Fig. 9, Plate II.) Dug hole 4 feet down on north side, 3 inches in width and 3 inches in depth, in 6 minutes. Rear Panel No. 27. From top 2>< feet down very soft, like putty. Rod goes in full length of 3 feet, horizontally, into concrete, for dis- 57 tance of 2 feet down. Then rough I foot down, but not so soft. Thence'good to bottom. Lower 6 feet good. Old work, perhaps? At 2 feet down, dug out a bucketful of concrete with trowel. Soft mortar only and no stone. This was taken 2 feet below a batten left on piles for straight-edge for leveling off top of concrete. There appears to have been no slope made on rear upper corner of concrete mass at this place, as the face of wall reached up to the bat- ten placed for leveling off, and this batten was only II feet above bot- tom of wall apparently. Possibly, diver did not reach bottom by I foot, which would make batten in right place. Dug a hole in wall, 2 feet from bottom at south side, 6y z inches deep and 6 inches diameter, in five minutes. Best bottom (or one of the best) for smoothness yet examined rear of this wall. (See Fig. 8, Plate II.) Rear Panel No. 32. From top, soft 8 inches down. Face seems quite good for 6V 2 feet down, with soft places in it. From 6y 2 feet to 7)4 feet, soft right across the face horizontally. About 8 to %y 2 feet down the south end of panel is very soft ; this is a seam ; diver can put his hand in. There is a face to the wall, but it is very soft. Got down to the bottom. General character of face smooth but soft. Dug hole in face, 4 feet down on north side of panel, 6 inches deep, 6 inches diameter, in five minutes. Prettv soft ; could find very few concrete stones. REMARKS. First. Portland cement, with respect to the amount of clay — that is, silica and alumina — which the artificial mixture or the natural stone contains previous to burning, occupies an intermediate place between the ordinary hydraulic limes of commerce used throughout Europe, and the quick-setting argillaceous and argillo-magnesian cements, such as the Roman, the Vassy, the Rosendale, the Cumberland, and other Ameri- can cements. The hydraulic limes contain less clay than the Portland cement, and the quick-setting cements more. Second. During the burning of a stone which yields hydraulic lime, all the silica and alumina combine with lime, producing silicate of lime, silicate of alumina, aluminate of lime, and other combinations. These are the compounds, which, after water is added, undergo a species of crystalization, technically called setting, which constitutes the hydrau- lic property. But there is in the burnt product an excess of uncom- bined or quick lime, sufficient to cause it to slake to powder in the presence of water, in the same manner as common lime slakes, though much less promptly, especially if the excess of quicklime be small. A 58 paste of hydraulic lime is somewhat unctuous to the touch, and sticky and soapy, although less so than a paste of common lime. When a mass of it is placed in water, it will gradually enlarge itself laterally by- spreading out in all directions in consequence of its weight and plas- ticity. In doing so, it will usually present the same surface constantly to the water, and will not crack up into numerous pieces, or fall asun- der into a lumpy or granulated mass. Hence a mortar of hydrau- lic lime, if quietly deposited under water, will not generally become washed out so badly as to separate the sand from the lime, but the par- ticles of sand will be mechanically held in place by the lime paste during the time while the mass is assuming a state of rest and equili- brium, after which it will gradually indurate by setting. The water must be as quiet as possible, and all currents that might wash away the lime from the sand be avoided. Third. When a hydraulic lime, after burning, cannot be slaked to a powder or paste with water, but must be reduced by grinding, it is called a cement ; and, if it contain certain proportions of silica, alu- mina and lime, it will yield Portland cement. The composition of a mixture, whether natural or artificial, that will produce Portland cement, is such that, when burned at a high heat, the silica, alumina and lime enter into combinations with each other, and form those combinations which confer the hydraulic energy, leaving neither ingredient in excess as an adulterating constituent. It is to this cir- cumstance, in part, that Portland cement owes its superiority. When finely ground, a heavy, sharp, and minutely granulated powder (the Portland cement of commerce) is produced. If mixed with water into a stiff paste, it is, in great measure, destitute of those unctuous and adhesive properties which characterize a paste of common or hydraulic lime. It may be said to possess little cohesiveness until it begins to set, which ensues two, three or four hours after mixing, depending on its qualities. A plastic cake of it, immersed in water, will not gradually spread itself out in the same manner as the lime paste, but will, unless it be rather flat and thin, with gentle slopes on all sides, break down all around by the sliding off, successively, of the exterior portions, thus constantly presenting a new surface to the wash of the surrounding water, until it attains the angle of repose. When the cake is of such form that no cracking or disintegration takes place when immersed — that is, when it is comparatively flat and broad — it will set and harden with great energy under water. Indeed, the most advantageous con- ditions for its hardening are secured in the water, or in a constantly wet place, provided the initial set can begin in the open air, or the immersion can be made without drowning out the material, which always results in separating the finer from the coarser particles, and the loss of the former, in a greater or less degree, in the form of laitance, 59 and in the case of mortar in the separation of the cement from the sand, and the deposition of each material in layers or pockets by itself. In this process the sand, being the heavier of the two, will go to the bot- tom. The evil results are more serious with the slow than with the quick-setting pure cements, for the simple reason that the disintegra- tion is arrested as soon as the induration fairly begins. When any kind of hydraulic cement, or cement-concrete, is deposited in water, some of its lighter particles are washed out and held for a time in sus- pension in the water. They afterwards subside as a layer upon the top of the mortar or concrete, and, if not removed, interpose themselves between contiguous layers. As they possess very little, if any, hydraulic energy, they are elements of weakness in the mass in pre- venting the requisite continuity and bond. The French engineers call this material laitance. It is not only an injury in itself by producing seams in the mass, but it injures the quality of the cement from which it is extracted. Its volume will be great in proportion to the amount of washing to which the mortar is subjected in the process of its deposi- tion. Some cements receive more injury by washing, and yield more laitance than others. Fourth. When the Roman or the Rosendale cements, and cements of like character, are burnt, all, or nearly all, of the lime and magnesia which they contain enter into combination, with the silica and alumnia of the clay, in the formation of those compounds which confer the hydraulic properties, leaving, however, an excess of uncombined clay f which acts as an adulterating ingredient in the cement. The burning takes place at a lower heat, and the compounds formed crystalize a set more promptly than those of Portland cement. The free or uncombined clay in the product renders the paste ot these low-burnt cements some- what unctuous, cohesive and sticky. The powder is less granular, and possesses much less weight than Portland cement, and, when made into mortar, it seems to hold the sand better. If this is not, in fact, the case to any great degree, its quick-setting properties render it superior to a cement that sets slowly, for all kinds of submarine work where the mortar has to be immersed in the plastic state. Rosendale cement of active quality, if made into a plastic ball or sphere of ^ inch to i inch in diameter, and immersed in water, will harden without rupture or change of form, and, at the end of about an hour, can be rolled across a room upon the floor without breaking. No good Portland cement will sustain this test ; yet, if both be allowed to set in the air, and are then placed under water, or in a damp place for five or six days, the Portland cement, mixed with three and a-half times its volume of sand, will make as strong a mortar as Rosen- dale cement without sand. M. Leblanc, Engineer des Ponts et Chaussees (see Annales for 1865) GO says that heavy Portland cement only, such as weighs not less than 105 pounds to the struck bushel, should be used for important works — a statement which he could not have made had he been familiar with the best American cements, and the history and results of their use upon our public works during the last forty years. I have been a constant advocate of Portland cement as a substitute for Rosendale for general use, with certain marked exceptions, for the reason that, when very strong work is required, its superior strength gives it a great advantage, while for common masonry, in large masses, where inertia is desired rather than strength, it will bear adulteration with common lime and sand to such degree as to bring the cost of the work even below the cheapest that can be produced with the Rosendale, or any equivalent American cement. For the fabrication of concrete, however, to be deposited to take its first set in water, I have never recommended it, not because it is incapable of yielding excellent work under such cir- cumstances, but because the condiiions, necessary to secure excellence, can only be established and maintained under the most careful per- sonal supervision, such as a superintending engineer is seldom able to give. When those conditions can be secured there is no doubt of its superiority to Rosendale, or any other light, quick-setting cement. M. Leblanc further states, that Portland cement concrete, immersed in water, undergoes an energetic weakening, or washing-out ; that the broken stone, as soon as it touches the water, is deprived of its mortar, in fact, keeps no trace of it ; that Portland mortar is not fat and soapy like lime mortar, and does not stick to the trowel ; that, poured into sea water, this concrete arranges itself in three parts or beds, the upper portion being a thick, milky solution, with no power to set, and remain- ing soapy unless dried. The second portion resembles meagre mortar. The lower stratum alone appears to preserve its quality ; but being com- posed of the heaviest and most highly burned grains, it sets very slowly, and, besides, is weakened by mixture with the larger proportion of gravel forming the mortar, which talis down with it through the inter- stices of the broken stone. M. Leblanc also remarks that, when con- crete is deposited in water from boxes, they should be as large as prac- ticable, but that if it be absolutely necessary to use it under water, it is best to employ a tremie in preference to any other apparatus ; also, that Portland concrete may be spread out under water with less alteration than a bed of lime mortar concrete, provided, that steep slopes and the rolling of the stones on the surface are avoided, which can be accomplished sufficiently easy with the tremie. It is not attempted to give a transla- tion of M. Leblanc's paper, but only a summary of his opinions, so far as they bear upon the subject under consideration. He is an advocate of the use of freshly-mixed Portland concrete in the water, under such pre- cautions as will secure it against injurious wash. tt Fifth. It will be inferred from the foregoing- that, in order to produce good submarine masonry by depositing freshly-mixed concrete in the water, certain precautions are necessary, viz. : (a.) The cementing material should possess the properties of unc- uousness and adhesiveness to enable it to retain the sand while the concrete is assuming a state of rest in the water ; and it should be able, in as great degree as possible, to assume that state, by flattening out and spreading, rather than by breaking down and rolling off on the sides of the mass deposited. (&.) If it be deficient in the properties last named, it should in lieu thereof, be quick-setting, in order that the washing-out of the sand and its separation from the cement may be arrested in a few minutes after deposition, by the prompt induration of the cement. (c.) If a box is used for depositing the concrete, the torm of the box and the manner of emptying it should be such that the concrete will be subjected to as little wash as possible. Hence, a large box is preferable to a small one, as it will expose a less area of surface in proportion to the volume deposited. For example, a box 3 feet long by 3 wide by 2 feet high, will hold 18 cubic feet, and has a surface area of 42 square feet, equal to 2^3 square feet to each cubic foot ; while a box of the same form, but 6 feet wide by 6 feet long by 4 feet high, will hold 144 cubic feet, and has a surface area of only 168 square feet, equal to 1 1-6 square teet to each cubic foot. {d.) The form of the box used in laying the foundation of the King Street and Canal Street sections is objectionable. It has no cover on top, so that the exposed surface of the mixture, equal in itself to 1 square foot to every 2 cubic feet of volume, was subjected to a rush of water over it during its descent to the bottom, and the contents, instead of being deposited in their allotted place in a compact mass, issued in a manner much resembling a stream. Moreover, the side door of the box fitted so imperfectly, that the water entered quite freely around its edges and forced its way through the concrete to the top before the box became submerged. A box, operated on the clam-shell plan, would have been better; but preferable to any box is the trimie, when properly constructed and operated, as the con- crete laid with it never touches the water until it issues from the bottom of the trd?nie in the spot where it is to remain, without fur- ther disturbance, except what may be caused when the next layer is deposited upon it. It is laid under a constant pressure from the weight of the column of concrete in the trimie shaft, which, with a tremie 20 feet long, would amount to abou f \ l / 2 tons per square foot. A trimie is operated in a vertical position and is freely open at both ends. The spout used for a time by the Department of Docks, was closed at the lower end, and the concrete issued in a stream trom an 62 opening on one side. As a matter of course, it was badly washed. Sixth. A glance at the inspection notes shows that, while the con- crete is by no means good in average quality, and in many places is very bad, in the Canal Street and King Street walls, this inferiority differs in the two cases, both in kind and extent. The Canal Street wall is traversed by several bad seams of soft material, collected as sediment upon the surface of some of the layers of concrete, and, therefore, separating contiguous layers. In some places, a probe can be thrust into this mixture, by hand, to a depth of several feet, being finally arrested, apparently, by the broken stone in the con- crete, either above or below. Much of the material of these seams is entirely destitute of hydraulic properties, and does not get hard when dried, but becomes light, spongy and easily pulverized between the fingers. The laitance produced when Portland cement is placed in pure sea water is slightly hydraulic and, although its interposition as strata in the concrete breaks its continuity and impairs its strength as a monolith, the injury is trifling when the strata are thin and few in number, as they always will be when the work is vigorously pushed with thick layers. Seventh. That portion of the Canal Street wall which came under my inspection was the eleven uncovered panels in the rear, situated between the middle of Pier 34 and the north end of the wall. The seams here vary in width from y % inch to 3 inches, and, in depth, as ascertained with a probe, from 3 or 4 inches up to 3 feet. They are, doubtless, much deeper in some places . but, as they are interposed between undulating and irregular, instead of plane, surfaces, the probe would be stopped by the broken stone of the adjacent concrete. The material of the seams was generally of a whitish color, composed mostly of laita7ice, with some river filth and sewage. In several places, the bottom, or heel, of the wall is broken under to a depth varying in the different panels from 1 to 3 feet. This is due to the relatively inferior character of the concrete composing the bottom layer, which, on being emptied from the box, at the pile-heads, fell through the water a height of from 1 to 3 feet before it found a resting place on the broken stone. It was therefore subjected to severe washing, and parted with much of its cement and sand, the lighter por- tion of the cement floating away in the water, to be subsequently deposited as a seam, while the heavier particles, together with the sand, settled down among the rubble-stone below. Several soft places were found in the face of the concrete, besides the seams ; and some of these contained no stone, but only soft washed-out cement, or cement and sand, either mixed together or in separate layers. These weak places were, doubtless, caused by the settlement of cement, 63 sand and laitance into the depressions next the shutters, left between contiguous boxes of concrete, thus filling these depressions or cavities to such degree that the concrete subsequently deposited could not flow into and fill them. The concrete in the heart of the wall, as shown by the shaft sunk from the top, is superior to that on the back next the caisson, and, with the exception of a few seams, is of fair average quality. At the King Street wall the shutters had been removed from twelve panels on the front, and from seventeen panels on the rear, the whole number of panels being nineteen on each side, in a total length of 146^ feet. Diver Burt examined all the uncovered panels in front and rear. A second examination of those in front was subsequently made by Diver Conklin. The seams occur less frequently, and are fewer in number, and of less length along the face, in the King Street than in the Canal Street wall. They are also of less depth, as indicated by the penetration of the probe ; and, on the whole, do not constitute such an element of weak- ness as to require that any special precautions should be taken to guard against it. Eighth. The hardness ot the concrete in the two walls was fre- quently tried, in a rough way, by digging small holes in the face, care being taken to select spots where there was no exceptional soft- ness due to the existence of seams. The instrument used was a com- mon stone drill, 21 inches long, made from i-inch octagon steel, having on one end a dull chisel edge % inch wide. It was thought that, by employing the same diver with a similar drill at some future time, the progressive induration of the concrete could be approx- imately determined. The test-holes resembled in form the small end of an egg. The width at the face of the wall, and the depth, as well as the time occupied in digging the hole, was recorded in each case, and will be found in the notes of inspection. Nineteen of these holes — five in front and fourteen in rear — were dug in the King Street wall, and eight in that portion of the rear of the Canal Street wall, which came under my inspection. The holes were of various sizes, — from the smallest, which was 2]/ 2 inches deep and 3 inches wide, to the largest, which was 12 inches deep and 12 inches wide, and the time occupied in digging them varied from 3 to 1 1 minutes. The average depth of those in the King Street wall was 7 1-9 inches, the average width, 7 1-6 inches, and the average time required to drill them, 6 1-6 minutes. At the Canal Street wall the average depth was 5 1-5 inches, the average width, inches, and the average time, 5;^ minutes. These facts, although interesting, are only of practical value in connection with a future examination by the same diver with the same or a similar instrument. No hammer was used, but the drill was worked in with one hand. Ninth. A characteristic feature, which may correctly be termed a weakness of the King Street wall, is due to the comparative inferiority of the concrete, in the first or lower layer, deposited around and upon the pile-heads. The causes of this inferiority have already been mentioned. Its results are of a marked and somewhat import- ant character, for the toe of the concrete base is so badly broken off and caved under, that the front row of piles, located directly under it, give very little, if any, support to the wall, and should, for safety, be disregarded in calculating the stability of the structure. The effect cf this is to place the toe of the wall at the second row of piles two feet back, and, therefore, to diminish the thickness of the wall, at the base, two feet. As the piles of the second row, and of all the other rows in rear of it, except the one under the heel of the wall, were left extending above the rubble-stone, they doubtless have a good hold on the better concrete of the upper portion of the lower layer, or of the second layer, into which many of them reach. Another feature of the King Street wall is that, in many places, the face of the concrete base has fallen off to a greater or less depth through- out its entire height. In some panels the amount thus lost is trifling ; in others it averages nearly a foot in horizontal thickness ; while many preserve their original face almost intact. This loss of concrete does not increase the weakness caused by the breaking under of the toe of the wall, for the reason that the part lost is simply a portion of an over- hang, all of which could, without further impairing the stability of the structure, be spared as far back as a vertical plane tangent to the outer faces of the second row of piles. Besides the seams there are soft places, destitute of concrete stone, in some parts of the King Street base, but not near as many as were detected at Canal Street, owing, doubtless, to the circumstance that the box used in laying the former (2 cubic yards in capacity) held twice as much as the one used in laying the latter. Tenth. In filling the experimental caisson described in the joint report, the directions given were to execute the work under precisely the same conditions which obtained in laying the concrete base of the Canal Street section, which differed from the method followed at King Street only in the capacity of the box used. The object of that experiment was to illustrate the extent to which Portland cement concrete, deposited in the manner and with the appli- ances adopted in the construction of these walls, parted with its sand and the lighter portions of the cement. Besides the information sought, 05 and assuming that the instructions were faithfully executed, the experi- ment brought out the additional fact that the concrete in these walls, although rich enough in cement, was not thoroughly mixed ; at all events, not as thoroughly as I have always exacted upon government works, even were the concrete was made by hand ; while, in comparison with mill-made concrete, the degree of manipulation falls greatly below the average. Without going into lengthy details, it will suffice to state that the cement was not thoroughly and uniformly mixed with the sand, and the m.rtar was not well incorporated with the broken stone. Those familiar with this kind of work will readily admit that one additional turn with the shovels, if properly done, may convert an inferior mixture into a good one. Eleventh. In my opinion, the kind of cement used, the manner of mixing the concrete, the method and the apparatus employed in laying it, and the neglect of the workmen in allowing the laitance and river filth to remain upon the layers, are quite sufficient, when considered together, to account for the condition in which the works were found. The exceptional inferiority of the lower course of concrete is due to exceptional causes already mentioned. Twelfth. Instances may, and perhaps will be, cited, in which appar- ently the same method of construction in all its details, has given good results elsewhere. As a case in point, it has been reported to me, that the foundation of the light-house, now under construction on Race Rock, situated in Long Island Sound, some miles from New London, Conn., was laid in precisely this manner. Upon inquiry, however, I learn from the contractor that the concrete was thoroughly mixed by machinery ; that the box with which it was deposited had a close-fitting door on the side so that little, if any, wash came from that direction, and that in order to diminish the wash on top, as it had no cover, a thin layer of sand was spread over the concrete before the box was lowered into the water. It may be remarked, also, that this concrete was deposited in from 10 to u feet of water, within a boiler iron caisson, which is left in place as a part of the foundation. The material inside has never therefore been examined, except on top as the work progressed. Some importance should doubtless be attached to the fact that this work is located in clear sea water, while the dock walls stand in a mix- ture of sea water and sewage ; for although Portland cement, if mixed up with fresh water, may be deposited in sewage water without any more retardation of the set, except in the washed-out portions, and without any greater separation of the cement from the sand than would ensue in clear water, still the parts that are separated by the sewage water, consisting of the lighter particles of cement and the laitance, will never indurate at all. ' In the Canal Street and King Street 66 walls they constitute the seams and pockets already described. Simi- lar seams and pockets in the Race Rock foundation would in time harden to some extent, and therefore be less positively injurious. Thirteenth. It appears that orders were repeatedly given to remove the laitance and filth from the surface of each layer of concrete before the succeeding layer was put down, but the implements placed in the hands of the diver for that purpose— a street broom and a hoe— were not calculated to do the work effectively, even if faithfully used. They could only stir up the filth, to be held temporarily in suspension in the water, and in the end to become incorporated, to a greater or less degree, with the fresh concrete, and produce pockets and seams of washed-out material, much more injurious in character than would have been formed by washing with the impure river water alone. The usual way to remove laitance, and the only effective way that I know of, is to pump it out through a suction hose, with its lower end in the hands and under the control of the diver ; or the hose can be man- aged from above, and the services of a diver dispensed with. Fourteenth. An engineer may be willing to adopt a method of doing work which is to be executed under his constant personal supervision, or that of assistants selected and controlled by him, which he would hesitate to recommend to others who might not be similarly circum- stanced. Although I entertain no doubt whatever that, with proper care, good masonry can be made by depositing freshly-mixed concrete in water, and even in a mixture of sea water and sewage, still it must be con- ceded that the process is one into which elements of serious uncer- tainty can easily insinuate themselves, from a simple neglect, on the part of the workmen, of apparently unimportant details, and should there- fore be avoided whenever it is practicable to do so, and especially in cases where the engineer in charge cannot personally superintend the daily progress of the work, or is at all restricted in the selection of his agents. When I was called into consultation with General McClellan with respect to the material and method of construction to be adopted for the masonry portion of these bulkhead or quay walls, I recommended beton blocks, laid as alternate headers and stretchers, and I have seen no occasion to modify the opinions I then held. If I had the wall to build, as a government work, I would probably adopt the beton-in-mass method, in order to lessen its cost ; using Rosendale cement concrete containing some common lime, and deposit- ing it with a tremie, upon a close platform of planks resting on the pile- heads. Under those portions of the wall, where the layer of dock mud was found to be exceptionally deep, I would broaden the base of the piling by inclining the piles of the two outer rows ; but generally, where conditions more favorable to stability existed, I think the bed of 67 stone, placed around and in front of the pile-head, could be safely depended on to resist all outward movement from earth pressure in the rear. Respectfully submitted, Q. A. GILLMORE, ' Lieut. -Col. Corps of Engineers, Bvt. Major-General U. S. A. To the Commissioners of Docks, New York City, February 15, 1876. 68 LOG, AS KEPT BY MR. WORTHEN, OF REPORTS OF DIVER MR. JOHN BURT, AND EXAMINATIONS OF CON- CRETE WALL, CANAL STREET DOCK. Panel No. 3. October 28, 1875. Shutter raised for examination of face. Offset good, wall good. 1 foot down below offset, a soft seam ; ^f-inch drill can be forced in, in some places 1 5 inches, in some only 2 inches ; width of seam 1 inch. 4 feet down another seam, about the same as first seam, both extending across panel. 8 feet down a third seam, from 2 to 5 inches wide ; can run drill in about 18 inches. Felt down through the mud ; face seems good as far I can feel ; panel very good except seams. Time occupied in drilling hole, with a steel drill 21 inches long, 1 inch thick, pointed to % inch, 9 minutes ; no sort of hole, 2 inches in diameter by y z inch in depth ; location of hole between first and second seam, about 6 inches above second seam. Holes were invariably drilled by striking with the drill itself, without any hammer. Panel Nos. 4, 5 and 6. Shutters in. Panel No. 7. October 27, 1875. Shutter off. Granite wall commences. This panel was examined after panel 8 ; upper seam as before (panel 8), except that it gets wet again ; second seam, same as before, but not quite as wide ; third seam, same width all the way across. Could shove in drill 1 foot ; can put my arm and drill 2 feet under the foundation ; it seems as if a plank reached under south pile and extended northerly about 6 feet ; f-inch gas-pipe driven into lower seam 26 inches ; got it in, in two places ; drilled hole, y/ z inches deep by 4 across, in 6 minutes ; not quite so hard as others. Panel No. 8. October 27, 1875. Upper seam, about 3 inches wide, without cement, runs across panel. Outside stone can be pulled out by hand. Middle seam slight, but extends across ; drill cannot be shoved in. Lower seam, 1 foot wide, just the same as before. Drill shoved in whole length, does not seem to strike a stone. About 8 feet down, feel a little solid wall below. Face between seams pretty good, but chipped in a little in places. Offset good. Diver now took down a rod and marked position and width of seams. First seam, 26 inches down, 5 inches wide. Then 3 feet space. Second seam, 2 to 4 inches wide. 3.3 inches space. Third seam, 13 inches wide. To bottom, 2 feet. Panel No. 9. October 27, 1875. First seam widens (comparison 69 with 10). Specimen brought up : a bluish deposit, seemingly of cement and sewerage ; broke readily in the fingers, and, after exposure for some weeks to air, showed little, if any, signs of setting ; seam extends across panel. Second seam, about 4 feet down ; extends across panel ; no wider than in 10. Third seam, about 8 feet down. Specimen brought up from north side out of wall at the seam : soft, so as to be readily punched with drill ; seam, 1 foot wide ; balance of face of wall, except seams, not bad ; depth of face exposed, about 10 feet. Diver went down a second time with hoe and bucket, and brought up nearly a bucketful from third seam ; it was of a soft clayey consistency, probably cement and sewer deposit, which was left for some weeks in the shanty office at the dock, and showed no signs of setting. Panel No. 10. October 27, 1875. Seam still continues, and another seam of same kind, about 7^ feet down ; brought up a specimen of last ; a weak, bluish deposit, probably of cement and sewer deposit. Could not make a hole in face by striking with drill. Knocked off a few chips. Three seams all the way across panel ; first, 2 feet ; second, 4 to \% feet ; third, 7 feet down from offset. Face not as good as above, but pretty hard ; uncovered but little below 7 feet. Face good, with the exception of the seams. Panel No. 11. October 27, 1875. Same soft seam as in 12, but a little higher up, about 21 inches below offset ; runs across panel Drilled hole about 4^ feet below offset, \Y 2 inches deep, in seven minutes. Found two holes in face about 2 inches diameter. Could stick drill in one 20 inches, in the other, 1 foot. Panel No. 12. October 27, 1875. Soft seam, about 2 feet below offset. About across panel could shove drill in readily about 1 foot ; appears like a seam. Drilled hole about 2 feet below offset, 1% inches deep in eight minutes. Panel No. 13. October 27, 1875. Central panel, beneath pier, exposed for only 1 5 inches below offset. Face and offset good. Drilled small hole, about 3 inches deep, in five minutes. Panels Nos. 14 a?id 15. October 28, 1875. Could only get to off- set, which seemed good. Panels Nos. 16, 17 and 18. Shutters in. Panel No. 19. October 28, 1875. 21 inches down, a seam % inch wide across panel. 4 feet down could feel another seam, but old timber in the way. Face between seams good ; no place where stone can be pulled out of the face. Panels Nos. 20, 21, 22 and 23. Shutters in. Panel No. 24. November 3, 1875. 36 to 42 feet north of pier. Specimen brought up from offset, which is broken all the way across, about 1 foot down : a small seam across panel ; scantling in wall embedded about 3 inches down. Extends within 6 inches of south 70 end panel. Could push bar (^-inch chisel-pointed steel rod) into seam about 8 inches; seam,i to 1%. inches wide. Next 2 feet below seam : wall smooth and good. Next 1 foot bad, soft ; could stick bar in 18 inches, in places varying in width from 3 inches to 1 foot; could not get down onaccount of dock logs. Panels Nos. 25 and 26. Shutters in. Panels Nos. 27 and 28. November 3, 1875. 58 to 72 feet north of new Pier 34. Shutters taken off and posts between panels removed ; (72 feet) offset broken off and soft to 1 foot down ; could shove ^-inch bar in 8 inches. General face rough, with soft spaces in it, down 6 feet ; part of the shutters still in. No appearance of seams. (58 feet) brings up specimen of offset ; soft for about 1 foot down ; 2 feet more, rough with soft places. Next 3 feet down, good face ; 6 feet only exposed, drilled hole 4 feet down, 6% deep by 6 inches diameter, in 5 minutes ; could pick out stone. Specimen brought up of a fair set, but with streaks of cement deposit. Rear of Wall. Pa?iel No. 7. October 28, 1875. Top edge good, all the way across ; small seam from 12 to 18 inches down, very narrow ; got in y{ rod, in one place about 4 feet. Another very narrow seam, just felt it with the rod. Face of wall at 4 feet down, very rough, not as good below as above ; can get down about 7 feet. Panel No. 8. October 29, 1875. About y z of wall good ; seam, 1 foot down, from J^to 3 inches wide ; seam, 4 feet down, from 4 to 8 inches wide, at 5^ feet, face broken and rough ; about 7 feet of face exposed ; brought up specimens in bucket taken off with a hoe ; stone with but very little cement ; scraped in to the depth of 4 or 5 inches ; grows a little harder as you get in deeper. Panel No. 9. October 29, 1875. From top of wall down, 1 foot, generally soft ; can put in y% rod from 4 to 5 inches ; next 4 feet down, good. Then a break from 3 to 8*4 inches in depth to bottom of wall ; broken out entirely across panel ; face very rough, can pull out stone easily ; about same specimens brought as from last panel (8) ; could not reach any piles. Panel No. 10. October 29, 1875. The soft place in preceding panel (9) extends into this panel about 2 feet ; seam runs across panel 12" at south end, and 9" at north end. Below top of wall narrow seam ; could not penetrate, with Y% rod, above 3 inches ; face good for $ feet down ; then broken out, same as in last panel, across the whole face, clean to the bottom, from 6 to 8 inches deep ; could not get at any of the piles. Panel No. 1 1. October 29, 1875. Small upper seam, pitches toward 71 the north to 12 inches down ; very narrow; down to break all good ; below generally broken on face, but not, in any place, to more than a depth of 5 inches, clear across the face of the panel ; drilled for six minutes at a place about 3 feet down, but could not make a hole. Panel No. 12. October 29, 1875. Small seam, 1 foot down, narrow ; can get y% rod in from 6 to 8 inches ; face very smooth for 5 feet down, then the break commences, as in panels above. So many old piles that I could not examine fully from break-down, but, as far as tried, not more than 4 inches deep at any place. Could not get under con- crete at bottom ; felt one pile out beyond face of concrete. Panel No. 19. October 29, 1875. General face pretty good. 1 foot down, small }£-\nch seam across panel ; forced in rod about 3 inches. 4 feet down, a large seam \yi inch wide ; forced in the y% rod from 6 to 12 inches. Rip-rap some 2 feet below bottom of concrete. Could count 5 piles, but could not feel the head of any of them ; could feel in between the piles. General face appears to be pretty good. From top of stone to first seam, 9 inches ; from first seam to second seam, 18 inches ; width of second seam, 2 inches ; from second seam to bottom, 6 feet 7 inches ; then space of 2 feet to broken stone. Specimen of soft deposit broken from top. Drilled hole about 4 feet down, \}/ z inch deep by 2 inches diameter, in 6 minutes ; very hard. Panel No. 20. October 29, 1785. General face pretty good all the way down. About 2 feet down there is a seam in which the y&" rod could penetrate about 3 inches ; narrow all the way across. At about 7 feet down there is another seam about half-way across panel, not over y z inch wide ; could force y% rod in a little. Wall exposed for about 9 feet deep, then corner rounded and gone in about 2 feet ; could touch pile at south end about 1 foot under the wall. Mr. Radenhurst thinks it was made by diver closing up a hole. Work laid in June. Drilled hole, \y 2 feet down, 6 inches deep by 6 inches diameter, in 4 minutes. Stone came out easily. South end of concrete wall, westerly half . October 28, 1875. A good specimen brought up. This specimen was a large piece to which a cord was attached by the diver, and was drawn up by two men ; it had been detached from the wall, probably by the pulling up of a pile, and was alone by itself. On breaking it up, the set seemed very fair. Examined by General Gillmore. No marks of separation of sand from cement, but looks more sandy than the proper proportion, but no show of cement by itself. Bottom seems good as far as I could get between the piles ; upper edge somewhat rough. Easterly half of wall, face rough ; stone can be detached, but specimen before taken up fair for wall. Same all the way across ; can find no trace of seam. When the face is smooth the cement is good. Northerly end of wall, could pick up loose stone on top of slope, but pretty good beneath ; could 72 not run the y% rod into it ; found piles coming up through the con- crete. January 21, 1876. Made personal examination of shaft, which has been sunk in the interior of Canal street wall. Panel No. 9. Could not free shaft entirely from water. At the surface of the water, which was — feet below top of wall, concrete good ; no show of seam ; could not get X" mcn steel probe in at all. About 2 feet above surface of water, find thin seam ; got probe in 6 inches in one place, in another 2 feet. This seam extends entirely across north side of shaft. Just above this seam can break out con- crete a little with the probe. Same seam traceable half-way across west side of shaft; no trace on south or east side. At 10 feet down from top of wall, another seam on west, north and east sides ; no trace on south side. Probe cannot be forced in much ; in one place on the east side got it in 6 inches. Directly above this seam can break out concrete with probe. These consist mostly of deposits of cement and sand, from l / z inch to 1 inch thick, except in one place, in north- west corner, of 3 to 4 inches. The cement in these seams is washed and without any signs of setting, and corresponding in char- acter with those on the outside, which have not set after weeks' exposure in the air. K/ng Str cct Scct/on. SCCT/ON THROUCH A~B . )>esl Sir Plate /. of, A, tftr/.Z. JVy.S. ! 1 fYy. /& rtp.fr. 1 /a* pa Met *m~ *enr» eve Iff J>Vy. /.t. Iff W w w l si-s i if PJate //. . •focomjua ///////// Re/forf */■",> Insps'rt/o/t Canal St. Quay Wall, New Yom C/rr. muffed// m Bp PAVEL H 2O Ftp. 'J. PAA/£L A/°2Q. te, ill Ftp. J. /=>AAS£r/.,A/° /3- Jj j 1 n « ! Arr//o// Pane's . > v ?7. . 4 T?24. /VOHTH ir/vo /. . r?7. ) "7,. South e/va /'/////' /. ,s//o»/;/y »>V'//wav „, c ,, /iVf'/'fs//rt/t.s „/■ /'ff/t/'/.s on /'r/rr,>, -/'ft/t/f/, SY. , SVv //<>/* ,„ V/Vrv"/' Plr/// '. 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