of concrete as a support for a row of wood posts a foot square, which were put in every 5 feet to carry the footing above.  When these posts were securely wedged in place the tunnel was filled with rubble masonry.  This wall was strong enough to carry the weight of the portion of the monument over the subway, but the monument had to be supported to prevent its breaking off when undermined.  To support it thus a small tunnel was driven through the rubble masonry foundation just below the street level and a pair of plate girders run through it.  A trestle bent was then built under each end of the girders in the finished excavation for the subway.  The girders were wedged up against the top of the tunnel in the masonry and the excavation was carried out under the monument without any injury to that structure.

[Illustration:  THREE PIPES SUBSTITUTED FOR LARGE BRICK SEWER AT 110TH STREET AND LENOX AVENUE]

[Illustration:  SEWER SIPHON AT 149TH STREET AND RAILROAD AVENUE]

[Illustration:  CONCRETE SEWER BACK OF ELECTRIC DUCT MANHOLE—­BROADWAY AND 58TH STREET]

At 134th Street and Broadway a two-track structure of the steel beam type about 200 feet long was completed.  Approaching it from the south, leading from Manhattan Valley Viaduct, was an open cut with retaining walls 300 feet long and from 3 to 13 feet in height.  After all this work was finished (and it happened to be the first finished on the subway), it was decided to widen the road to three tracks, and a unique piece of work was successfully accomplished.  The retaining walls were moved bodily on slides, by means of jacks, to a line 6-1/4 feet on each side, widening the roadbed 12-1/2 feet, without a break in either wall.  The method of widening the steel-beam typical subway portion was equally novel.  The west wall was moved bodily by jacks the necessary distance to bring it in line with the new position of the west retaining wall.  The remainder of the structure was then moved bodily, also by jacks, 6-1/4 feet to the east.  The new roof of the usual type was then added over 12-1/2 feet of additional opening. (See photographs on pages 46 and 47.)

[Illustration:  CONCRETE SEWER BACK OF SIDE WALL, BROADWAY AND 56TH STREET]

[Illustration:  LARGE GAS AND WATER PIPES, RELAID BEHIND EACH SIDE WALL ON ELM STREET]

Provision had to be made, not only for buildings along the route that towered far above the street surface, but also for some which burrowed far below the subway.  Photograph on page 47 shows an interesting example at 42d Street and Broadway, where the pressroom of the new building of the “New York Times” is beneath the subway, the first floor is above it, and the first basement is alongside of it.  Incidentally it should be noted that the steel structure of the building and the subway are independent, the columns of the building passing through the subway station.

[Illustration:  DIFFICULT PIPE WORK—­BROADWAY AND 70TH STREET]