The location of the lined sections is shown is the following table: In lining timbered sections as much of the timber as practicable is removed the rubble is placed. When the removal of the timber is too dangerous a care: amination is made, all unsound pieces are replaced, and all vacant places filles. rubble masonry and concrete. In the heavy ground in the west heading Char avenne shaft, the thickness of the arch has been increased from three to four b for a distance of 264 feet. The following is a résumé of operations in each heading-extracts from the rep Mr. George H. Coryell, assistant engineer, who has been in immediate charge work: EAST SHAFT-WEST HEADING. September 3, 1886.-Resumed active operations in drilling and driving the t heading. NOTE. For the fiscal year 1887, in addition to the above, 23 linear feet constructed to the he springing line. The sections where dry-stone packing and rubble masonry were used are as folle viz: Also 2756 to 2779-23 linear feet constructed to height of springing line. 1.94 East heading, Champlain avenue shaft. Heading turned May 21, 1884; heading completed June 30, 1887. Total distance, 348 feet. The sections where dry-stone packing and rubble masonry were used are as folows, viz: The following will show sections where brickwork of four rings have been used, viz: NOTE. The invert in the above sections were not added to, except between stations 815 and 846 an additional ring of brickwork added, making it three rings thick, Heading turned May 21, 1884. Heading completed Nov. 9, 1885. Total distance, 2,062 feet. NOTE.-For the fiscal year 1887, in addition to the above, 141 linear feet constructed to the height of springing line. Heading turned January 27, 1884; heading completed November 14, 1:85.7 distance, 3,124 feet. NOTE.-Length timbered temporary. No allowance made in estimates not excavated to timbere NOTE.-About 650 linear feet excavated for lining in 1886 allowed in 1887. West heading Rock Creek shaft. Heading turned January 27, 1884; heading completed January 5, 1886; to distance, 3,552 feet. NOTE. In addition to above 63 linear feet constructed to the height of springiz line. NOTE.-Seven linear feet of above temporary, and not allowed in the estimates not excavated to timber section. Excavated for lining: 1884. Length 1885. Length 1886. Length 1887. Length Total 1,26 1,3 OTE.-350 linear feet excavated in 1886; allowed in 1887. Foundry Branch shaft; east heading. Leading turned February 12, 1884; heading completed January 8, 1886; total disce, 2,875.7 feet. NOTE.-The above was enlarged for lining in 1886; allowed in 1887. West heading, Foundry Branch shaft. Heading turned February 13, 1884; heading completed July 31, 1885; total disace, 2,208 feet. Heading turned June 17, 1884; heading completed December 15, 1884; total disnce, 209 feet. The balance available for continuing the work is $123,837.70. At the present rate progress this amount will be expended on or before the 1st of November. The contractors, Messrs. Beckwith and Quackenbush, have exhibited zeal and inlligence in the prosecution of the work. A higher rate of progress could have been stained in lining the tunnel, had it not been evident that the work must be suspended r lack of funds. The estimate submitted in 1885 was based upon the assumption at dry-stone packing was to be employed in lining. The substitution of rubble asonry has largely increased the cost. At the time that estimate was computed but 3,500 feet of the tunnel had been excavated, and the character of the remaining rock as entirely a matter of conjecture. The bore of the tunnel has now been completed, nd the character of the rock can therefore be accurately determined. A careful inestigation has been made and it is found that much more of the rock than was then sumed will require lining. In addition to the 6,110.5 feet which has already been ompleted there, there are 1,915 feet of the tunnel which will require lining through. 8872 ENG 87-161 out, being in a rock liable to disintegrate from the action of water. The causes integration are generally impure talc and an excess of mica and iron pyrites. 4,100 feet is through rock, which, though not liable to disintegrate, contains s and seams which cause it to break irregularly, and both the roof and sides will y lining. As the bottom of the tunnel forms a firm foundation no invert will be rep in these sections. For a distance of about 3,000 feet the side-walls are firm and pact, but the roof will require support. The remaining 5,761 feet appear to be 21 and compact rock, not liable to disintegration. The question whether these ser should be left without any support is worthy of careful consideration. When the nel is filled with water its walls will be exposed to a pressure of over 50 port square inch. What the effect of this pressure on the bare rock will be is diff determine. The conduit is of a novel character, and from preceding experie little information can be derived. Under the pressure of the water may not the break in such a manner as to endanger the stability of the roof, i. e., pieces whi form a key fall out and the tunnel fill with the débris? It is known that in rock" seemed compact when originally excavated cracks have afterwards appeared. ▾ the tunnel is filled, and water introduced into the city, any repairs will be a so" great delay and expense. Without the tunnel be tested by being once filled water and afterwards examined, I do not consider that it would be safe to lear portion of the roof unsupported. The sides through these sections can then be lef rock without serious danger. When the tunnel is filled, if the rock breaks up ⠀⠀ remain in place unless the lower plane of cleavage makes an acute angle with the of the tunnel. While this may take place to some extent, it is not considered port for it to be sufficient to endanger the stability of the arch. The various forms of lining recommended are shown on the accompanying tra The estimate of the cost of the work is as follows: The following is a detailed estimate of the cost of excavation and lining: EXCAVATION. 1,609 feet timbered section (167.3 square feet), 9,970 cubic yards, at $8... 120 feet timbered section (143.4 square feet), 637 cubic yards, at $8.. 6,296 feet lining section (109.67 square feet), 25,573 cubic yards, at $8... LINING. Brick, 8,025 feet (32.3), 9,898 cubic yards, at $14. Dry stone packing, 1,489.6 feet, 4,936.72 cubic yards, at $2.50... SECTIONS LINED WITH ARCH AND SIDE-WALLS. 4,100 feet excavation (105.38), 1,600 cubic yards, at $8 |