sible from the bottom, and the tunnel had been lined for a length feet with brick increased overhead at the most exposed portions inches in thickness (4 bricks). The space between the brick an. the wood overhead and between the arch ard the rock in place sides had been filled in with dry stone packed as closely as poss. While it is probable that wood in such positions will be covered mately by water, this will not be true until the tunnel is filled; & the mean time dry rot may be at work among this wood, as was s be the case with the beams in several localities. But even if this b so, the wood from its elasticity, especially when laid up under suc. advantages, can not be trusted to transmit the pressure tending to ure the brick arch when the tunnel is filled. The Board therefor siders that before the work is completed all wooden backing shot replaced by solid masonry by means of auxiliary drifts run over the nel and filled solid with masonry, or by a new tunnel around the of the cave, filling up the present tunnel with masonry, or by a sunk at the locality, as may prove to be most economical. In these recommendations the Board has considered that the cor pressure due to ground water or to water filtering through the of the tunnel, is too uncertain and too liable to variation at dife localities to be counted upon to give a sufficient support to the lining. In a case like the present, where a serious injury would e consequences so disastrous, the brick work should be backed so so as to serve merely as a vehicle for transmitting the pressure to the in place. In the valleys of Rock Creek and Foundry Creek, which points where the ground is 135 and 50 feet respectively below the w surface in the reservoirs, and where the unbalanced pressures probably reach 58 and 21 pounds per square inch, all the lining backing wherever the rock is not unchanging and impermeable sh be done with the greatest care in the most substantial way and mortar rich in cement. This rule should also apply for considerable distances from t valleys, since rock seams leading from the tunnel into these or o depressions might much reduce the head of ground water, which wo otherwise exist there, to balance the internal pressure upon the li of the tunnel. The inspection of the new reservoir satisfied the Board that the w is proceeding in an entirely satisfactory manner as proposed by special Board of 1885, and this Board has no changes to recommend The total length of the tunnel when completed will be 20,700 fe and the engineer in charge states that the aggregate length then lit will in round numbers be about 12,000 feet, of which about 2,475 fe will probably have been timbered. At the present time, 1,740 have been lined and 1,175 feet timbered, these lengths being includ in the above figures. Respectfully submitted, Col. of Eng, J. C. DUANE, Lieut. Col. Eng. and Brt. Brig. Gen Lieut. Col. of Eng. and Bvt. Brig. Gen. Brig. Gen. JOHN NEWTON, Lieut. Col. of Engineers. APPENDIX V V-REPORT OF MAJOR LYDECKER. LETTER OF MAJOR G. J. LYDECKER, CORPS OF ENGINEERS. OFFICE OF THE WASHINGTON AQUEDUCT, Washington, D. C., September 7, 1886. SIR: By order of the Acting Secretary of War, I have been furnished for my guidce with the inclosed copy of the report of the Board of Engineers for fortifications d for river and harbor improvements in relation to the methods (1) of lining the nnel and (2) of constructing the new reservoir, for increasing the water supply of ashington, D. C., made in pursuance of the deficiency act approved August 4, 1886. As to the reservoir, the Board reports that "the work is proceeding in an entirely tisfactory manner," and no changes are recommended. As to the tunnel lining, the Board holds that the exclusive use of concrete is imacticable, indorses the use of the brick arch as now constructed, but recommends at the filling between the arch and the rock in place be done "with rubble laid in ment mortar, or with fine concrete packed solidly around larger stones, according convenience" instead of with dry stone as heretofore. The recommendation of the Dard, as I understand the act of Congress, is conclusive as to the method of lining be followed; so that the great question now to be determined is whether this work all be done "under the contract heretofore made or by a reletting." If the present contract included prices for the "rubble masonry" and "fine conete" recommended by the Board, I should have no hestitation in recommending at the work be continued under this contract; but such is not the case, and if the ork is done by the present contractors, without a reletting, it will be necessary to gree upon a price for this large amount of work, aggregating at least 25,000 cubic yards masonry, exclusive of the brickwork. But the contractors claim that they have a ontract to complete this tunnel, and that the specifications and articles of agreement ake provisions for dealing with any change of plan that might be determined upon uring the progress of the work. If it is held that the contract, when made, was for ny more work than could be done with the money at that time appropriated by Conress, the contractors may be correct in their claim; but that is a legal question which is useless for me to discuss further, and I introduce it only to suggest that the conactors are probably prepared to interpose every legal obstacle in the way of putting her parties on the work, whereby delay, damage, and increased expense would reult. The specifications describe the work to be done as "the construction of 20,826 eet, more or less, of tunnel about 11 feet wide and 74 feet high from the present istributing reservoir above Georgetown to the proposed new reservoir east of Howard Jniversity." They further provide for masonry lining "wherever required,” and eserve to the engineer in charge the right "to modify them (the specifications) whenever, in his opinion, it may be necessary for the proper accomplishment of the object in view." Referring to the articles of agreement, they provide as follows: "If, at any time during the prosecution of the work, it be found advantageous or necessary to make any change or modification in the project, and this change or modfication should involve such change in the specifications as to character and quanity, whether of labor or material, as would either increase or diminish the cost of he work, then such change or modification must be agreed upon in writing by the contracting parties, the agreement setting forth fully the reasons for such change and giving clearly the quantities and prices of both material and labor thus substicuted for those named in the original contract, and before taking effect must be ap roved by the Secretary of War: Provided, That no payments shall be made unless such supplemental or modified agreement was signed and approved before the obliration arising from such modification was incurred." The foregoing presents all the salient features of the case, and, after the fullest consideration, I have reached the conclusion that it will be "most promotive of the interests of the Government" and of the work to do the work of lining under the ontract heretofore made with Beckwith & Quackenbush, if satisfactory prices therefor can be agreed upon. It has already been determined to continue and complete he work of excavation under this contract, and that work is in full blast; there is a large amount of rock trimming that will have to be done before the lining is placed in that part of the tunnel already excavated through by these contractors, which they would have to do without additional compensation; they have their tracks, hoisting machinery, pumping machinery, and all other necessary appliances in place and are therefore ready to proceed with the work at once; they have considerable material for lining on hand, delivered last year, before the work of lining was suspended in order that the small balance of funds then available might be applied solely to the work of excavation; they have proven themselves to be reliable and energetic in their work; they claim it as a legal right to complete it, and would undoubtedly seek to maintain that right. In fact, the necessity of fixing a price, without competition, for the large amount of masonry of the kind recommended by the Board is the only material objection that occurs to me against the adoption of the course indicated above; nevertheless this is exactly the line of procedure tha pears to be contemplated in the articles of agreement to meet the reqareme 1. ** change of project, such as is now in question. If that course be approved I suggest, and request, that a board of engineers of not less than three met: designated to consider and report upon the question of price. Copies of the advertisement, specifications, and articles of agreement (blank prised in the contract, are transmitted herewith for ready reference. Very respectfully, The CHIEF OF ENGINEERS, U. S. A. G. J. LYDECKER [First indorsement.] OFFICE CHIEF OF ENGINEERS. 1. S. ARMY September 16, 1- Respectfully returned to Major Lydecker for an estimate of the amount and e the work proposed, and for a statement of the price at which the contractors w the work, and for Major Lydecker's recommendation in connection therewith. By command of Colonel Parke, in charge of office. Respectfully returned to the Chief of Engineers, U. S. Army. The exact amount of work to be done in lining the tunnel can not yet be stated from present indications it is estimated in round numbers that 12.500 cubie v... brick masonry, 4,500 cubic yards concrete, and 23,000 cubic yards rubble masonry be required, the last item being in lieu of the dry stone packing contemplated in original method of construction. The cost at prices named in the letter transm herewith, as those at which the present contractors will do the work, would be as lows: 12,500 cubic yards brick masony, at $14 4.500 cubic yards concrete masonry, at 85 23,000 cubic yards rubble masonry, at $4.75. Total.... $177 30. These prices make an average of about $7.67 per cubic yard for the total 4" cubic yards of composite masonry in the tunnel lining. I do not believe that a letting would result in anything less, and accordingly, as instructed in the forege indorsement, I recommend that supplemental articles of agreement for doing work of lining in the modified manner as required by the report of the Boars Engineers, be entered into with the contractors now on the work, based on prices: to exceed those named above. G. J. LYDECKER, [Third indorsement.] OFFICE CHIEF OF ENGINEERS, U. S. ARMY, Respectfully returned to Major Lydecker, to state how much money will be availab for the work proposed under supplemental contract. By direction of Colonel Parke, in charge of office. H. M. ADAMS, Captain of Engineers. [Fourth indorsement.] OFFICE WASHINGTON AQUEDUCT, Respectfully returned to the Chief of Engineers, U. S. Army. As nearly as I can estimate at this time it is probable that we will have abou $86,000 available for the work proposed under the supplemental contract, i. e., fo rubble masonry in tunnel lining. (Four inclosures herewith, including originals.) G. J. LYDECKER, [Fifth indorsement.] OFFICE CHIEF OF ENGINEERS, U. S. ARMY, espectfully returned to Major Lydecker, with directions to prepare a supplemental ract, to be submitted to the Secretary of War. spenditure under this supplemental contract to be limited to the amount availfor the purpose specified, after deducting such amounts as will be required for neering expenses. y command of Brigadier-General Duane. espectfully returned to the Chief of Engineers, U. S. Army, with proposed suppleatal contract, in quintuplicate, for consideration of the Secretary of War. he extension of the original contract with Beckwith & Quackenbush to June 1887, heretofore made with the approval of the Secretary of War, applied only to work of excavation and the removal of excavated material from the tunnel." my present recommendation is approved, that extension should now be made to ly to the work of tunnel lining also, as it is proposed to do the brick and conte part of this work under that contract at the prices bid at the original letting. G. J. LYDECKER, Major of Engineers. MMUNICATION ACCOMPANYING THE SECOND INDORSEMENT ON THE FOREGOING LETTER. GEORGETOWN, D. C., September 29, 1886. DEAR SIR: In reply to your communication of the 21st instant, while we do not adat the power to abrogate without cause our contract, or any part of it, and respectlly reserve all our legal rights thereunder, still, subject to this reservation, we are lling to agree to a modification of the contract, so that instead of “dry stone packg" there shall be substituted either or both of the methods mentioned in your letter. We therefore name the following prices as requested in your letter, viz: Eleven thousand five hundred cubic yards brick masonry, 4,500 cubic yards conete masonry, the price provided by the existing contract. Twenty thousand cubic yards rubble masonry laid in cement mortar for the price $4.75 per cubic yard. Twenty thousand cubic yards of fine concrete packed solidly around larger stone the price of $6.50 per cucic yard. Very respectfully, G. J. LYDECKER, Major of Engineers, U. S. A. BECKWITH & QUACKENBUSH, Contractors. LETTER OF THE CHIEF OF ENGINEERS. OFFICE OF THE CHIEF OF ENGINEERS, SIR: Your letter of September 7, inclosing the supplemental contract with Beckth & Quackenbush, transmitted with your indorsement of 18th instant, was subtted to the Secretary of War, indorsed as follows: [Seventh indorsement.] OFFICE CHIEF OF ENGINEERS, U. S. ARMY, Respectfully submitted to the Secretary of War, with recommendations that the plemental articles of agreement herewith be approved, and that the original conct herewith be extended, to include the tunnel lining, to June 30, 1837, as proposed Major Lydecker. J. C. DUANE, Brig. Gen., Chief of Engineers. And was received back with the following indorsement: Eighth indorsement | WAR DEPARTMEN), The recommendations of the Chief of Engineers are approved. JOHN TWEEDALI Three copies of the supplemental contract are herewith returned to be dispose accordance with law and regulations; one copy has been sent to the office of the se Comptroller to be filed with the original contract, and one copy is filed in this The report of the Board of Engineers, dated August 24, 1886, the blank specifican etc., the blank articles of agreement, and the letter of Beckwith & Quack-z dated September 29, 18×6, received here with your letter, are also inclosed. By command of Brigadier-General Duane. Very respectfully, your obedient servant, Maj. G. J. LYDECKER, Corps of Engineers. JOHN G. PARKE, Colonel of Engineers, Supplemental articles of agreement entered into this 18th day of October, 1× tween Maj. G. J. Lydecker, Corps of Engineers, U. S. Army, of the tirst part Clinton Beck with and John V. Quackenbush, partners, doing business under firm name of Beckwith & Quackenbush, of Mohawk, of the county of Herk State of New York, of the second part. Whereas on the 29th day of October, 1883, the parties above mentioned er: into a contract for the construction of a tunnel for increasing the water supp Washington, D. C., which provided, among other things, for placing dry stone ing in connection with the lining of said tunnel at a stipulated price per cubie yand Whereas the Congress of the United States, in appropriating for the complete the work, in the general deficiency act approved August 4, 1-86, instructed they retary of War "to submit to the Board of Engineers for Fortifications and for E and Harbor Improvements whether any changes are demanded for reasons of sa or economy in the method of lining said tunnel heretofore adopted and pursue. and Whereas the Board of Engineers aforesaid, in its report dated August 24, 186 quires the use of "rubble laid in cement mortar or (with) fine concrete packed so around larger stone" in lien of the dry stone packing herein before referred to, ther making necessary a modification in the original project such as involves a chang which the cost of the work will be increased: Therefore, in order to provide for modification aforesaid in accordance with the provisions of the original contract da October 29, 1883, This agreement witnesseth, that the said Maj. G. J. Lydecker, Corps of Enginee for and in behalf of the United States of America, and the said Beckwith and Quack. bush, for themselves, their heirs, executors, and administrators, have mutually agres and by these presents do mutually covenant and agree, to and with each other follows: That the said party of the second part, in consideration of the extension of original contract to include the work of lining that may be done under the appropr tion made by the act approved August 4, 1886, herein before referred to, and of p ment to be made as hereinafter provided, shall furnish all material for, and pls rubble laid in cement mortar wherever required in the tunnel, all as directed by a to the entire satisfaction of the party of the first part. In consideration of the material being furnished and the rubble laid as provided i in the foregoing paragraph, the said party of the first part shall pay to the said par of the second part at the rate of $4.75 per cubic yard; all payments being subject the conditions named in the original contract. It is expressly understood and agreed that all provisions of the contract entered in on the 29th day of October, 1883, between the parties herein named shall apply to th work and material provided for by these supplemental articles of agreement in so fa as the said provisions are deemed applicable by the party of the first part; and tha neither these supplemental articles of agreement nor any extension of the origina contract whereby it is made applicable to the work on the tunnel provided for by th general deficiency act approved August 4, 1886, shall obligate the United States any expenditure in excess of the amount thereby appropriated, after deducting there |