was again resumed early in November. Air pressure has varied from 17 pounds to 34 pounds.

The Manhattan headings have been advanced entirely through soft ground, while in the Brooklyn land headings rock was encountered in the bottom of the tunnel for the first 50 feet from the shaft, all other excavation being in soft ground. The end of this section in Manhattan is 1,600 feet west of the shaft and the headings will be excavated through soft ground, while in Brooklyn the end of the section is 2,000 feet east of the shaft, and, except as above noted, will also be wholly in soft ground. Soft ground excavation will also be encountered for a distance of 500 feet east of the Manhattan shaft and 750 feet west of the Brooklyn shaft. Between these two points, a distance of 2,300 feet, the borings indicate that all excavation will be through rock.

It is gratifying to note that even under the unusual present difficulties in obtaining construction materials, the contractor has stored on the work about 90 per cent of the heavy cast-iron tunnel lining required for the soft ground headings, so that there will be no delays due to the scarcity of materials for this part of the work.

The tops of the tubes near the Brooklyn pierhead line (about 500 feet west of the shaft) lie above the original river bottom, and during the year the contractor has dumped clay and rip-rap for the permanent cover over the tubes and an additional blanket of clay for construction purposes at this point, amounting to 185,000 cubic yards of materials.

The progress made in driving the different tunnel headings is summarized as follows:

* One-half of distance between Brooklyn and Manhattan shields.

Route No. 8, Section No. 4.- This contract covers the construction of two stations, one located between Bedford and Driggs avenues on North 7th street, and the other between Union avenue and Lorimer street on Metropolitan avenue. It also includes fan chambers and emergency exits located at Havemeyer street. and at a point east of Leonard street. Work was begun in 1916, but comparatively little progress made. During the year the contractor's work consisted largely of excavation for the First Subway structure, of which the greater portion was in Metropolitan avenue, excavation in North 7th street being undertaken during the latter part of the year. The excavation in Metropolitan

avenue from Union avenue to the end of the section near Manhattan avenue is practically complete, and that in the block between Roebling and Havemeyer streets on North 7th street nearing completion.

In advance of excavation for subway construction, it was necessary, because of the narrowness of the streets and the fact that ground water was found but a short distance below the street surface, to underpin nearly all of the buildings adjacent to the subway on both sides of the streets. This underpinning was done in the case of nearly every building. The buildings varied from small two-story frame structures to six-story masonry apartment houses and factories. Two distinct methods of underpinning were adopted, depending upon the location of ground water beneath the street surface. Where ground water was low enough to permit of such a method, underpinning was done by excavating open pits to about the depth of the subway excavation, filling them with concrete, and carrying the fronts of the buildings by means of reinforced concrete beams supported on the piers built as above described. In a large number of cases, however, the ground water prevented the excavation of open pits, except for a few feet in depth, and it was found necessary to adopt other means of supporting the buildings. In such cases piles were used. These were forced into place by hydraulic jacks reacting against the bottoms of the existing foundations of the buildings.

The piles consisted of sheet steel cylindrical shells 14 inches in diameter in short sections, forced into the earth by jacks, the interior soil being later removed by means of miniature orange peel buckets, post-hole shovels, etc., the process continuing until a

desired depth, usually about the subgrade of the subway, was reached, at which stage the shells, after being cleaned out, were filled with concrete. Wherever the weight of the building was sufficient, these piles were tested to 50 per cent overload by means of the hydraulic jacks. Such tests have shown that the piles are capable of carrying, without appreciable settlement, an average load of 30 tons each. The fronts of the buildings are carried by reinforced concrete beams supported on these piles in the same manner as the buildings supported on concrete piers. During the time the work of placing the piles and the reinforced concrete beams was in progress, the loads of the buildings were supported on temporary needles and timber shoring as required. The character of the material encountered varied greatly, consisting in some cases of the most compact clay, and in others of very soft material, boulders, sand, etc. Because of this fact, and the presence of a considerable amount of water, the work of underpinning progressed somewhat slowly, it being necessary to use extreme caution, as in many cases the buildings were old and very poorly constructed. Notwithstanding this, the work was advanced with fair speed, and the underpinning is nearing completion.

The building of the subway structure has not progressed as rapidly as might be desired, the delay being due primarily to the difficulty of obtaining steel for the work. Some steel has, however, been received and erected, and the entire subway structure between Leonard street and the easterly end of the section near Manhattan avenue, including concrete, waterproofing, etc., has been completed. Floor concrete and waterproofing are also in place ready for the erection of steel, from the center of the block between Union avenue and Lorimer street to the center of the block between Lorimer street and Leonard street.

The percentages of the principal items of work completed are as follows:

About 24 per cent of the total estimated value of the work is complete.

Route No. 8, Section No. 5.- The work on this section consists of constructing a double-track subway, including two stations, one located at Graham avenue on Metropolitan avenue, and one at Grand street on Bushwick avenue. It includes, also, emergency exits and ventilating chambers at Devoe street, Powers street, Maujer street and Stagg street. Construction was begun in 1916, but was advanced with little progress during that year. Good progress was made during 1917. All excavation is complete, except a portion at the intersection of Grand street and Bushwick avenue. As in the case of Section No. 4 described above, a considerable amount of underpinning was required, nearly every building, on each side of the streets, being underpinned in advance of subway excavation. Work on this section was not, however, complicated by the presence of ground water, as in the case of Section No. 4, and the underpinning throughout was done by means of open pits filled with concrete and the buildings supported on reinforced concrete beams beneath the fronts of the buildings, as described under Section No. 4. The character of the buildings varied greatly, but there were very few large or exceptionally heavy buildings to be supported. The work of underpinning is entirely complete.

The work of subway construction on this section has also been delayed somewhat by reason of the contractor's inability to obtain prompt deliveries of steel. Fair progress has, however, been made, and the entire subway structure, including concrete and waterproofing, from the westerly end of the section adjoining Section 4 on Metropolitan avenue to Graham avenue, on Bushwick avenue north of Grand street, and from south of Grand street to the southerly end of the section at Meserole street, is complete. The total length of the completed structure is about 1,700 linear feet.

The restoration of subsurface structures, including gas and water mains, duct lines, the backfilling of the street, etc., is in