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��Popular Science Monthly
���The new local tracks beneath Lexington Avenue near 74th Street. It will be noticed how free the street is from serious obstruction. This system, extended in a single track, would reach from New York's city hall into the borders of Eastern Tennessee, some six hundred and twenty-one miles
These are some of the more striking- features of the work ; but even the mat- ter-of-course features loom big- when one comes to inspect them closely. To make room for the subways, the space just below the street level has to be va- cated of all its various pipes. The ex- pense of moving them is enormous. Take, for example, one item, the cost of relo- cating sewers. Sixty miles or more of new pipes are being laid. The bill for these changes comes to more than six
��million dollars. One of the largest of the diverted sew- ers is in the neighborhood of the Pennsylvania Station, at Seventh Avenue and Thirti- eth Street. Now that a new subway is coming up Sev- enth Avenue, this sewer is being rebuilt to give outlet into North River — at a cost of fi^"e hundred thousand dollars.
Or consider the fact that while construction is in progress under the street, many gas-mains must be carried over the roadways on trestles. The average cost of doing this is twenty- fi\e hundred dollars ; and v.here larger distribution mains must be handled, the cost runs as high as ten or eleven thousand dollars.
Street-Cars and IVagons Carried on Dry-Land Bridges Or, again, in accounting for where so many millions must be spent in building subways, consider that the engineers never vacate more than half of the roadway at a time, and that the street- railways overhead and all the stream of vehicles and pedestrians are literally car- ried, while the digging is in process, upon miles and miles of dry-land bridges. They are the longest bridges in the world, and bear as much traffic as the busiest in the world. Then, too, hundreds of buildings must be shored up, for many of them are not built upon the solid rock ; and rotten strata of treacherous stone must be braced to prevent slides. In a number of instances buildings had to be torn down. The famous old Astor House was one of these. It stood on sand at a corner under which a tube had to pass. But one of the most ticklish operations of all is a section of new subway in WiU liam Street, where the underlying mate-
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