Today more than ninety-nine per cent. of the population of the immensely populated island of Manhattan lives north of the City Hall. That cheap north wall, hidden under countless coats of white paint, is the one acute reminder of the days that were when the Hall was new—when the gentle square in which it stood was surrounded by the suburban residences of prosperous New Yorkers and when the waters of the Collect Pond—where the New York boys use to skate in the bitterness of old-fashioned winters—lapped its northerly edge. There was no ugly Court House or even uglier Post Office to block the view from the Mayor's office up and down Broadway. New Yorkers were proud of their City Hall then—and good cause had they for their pride. It is one of the best bits of architecture in all America. And an even century of hard usage and countless "restorations" has only brought to it the charm of serene old age.
But the City Hall long since was outgrown. The municipal government of New York is a vast and somewhat unwieldy machine that can hardly be housed within a dozen giant structures. To provide offices for the greater part of the city's official machinery, this towering Municipal Building has just been erected. And because it is so typical of the best form of the so-called skyscraper architecture, let us stop and take a look at it, listen to the story of its construction. In appearance the new Municipal Building is a gray-stone tower twenty-five stories in height and surmounted by a tower cupola an additional fifteen stories in height. In plan the structure is a sort of semi-octagon—a very shallow letter "U," if you please. But its most unusual feature comes from the fact that it squarely spans one of the busiest crosstown highways in the lower part of the city—Chambers street. The absorption of that busy thoroughfare is recognized by a great depressed bay upon the west front—the main façade of the building. And incidentally that depressed bay makes interior courts within the structure absolutely unnecessary. So much for the architectural features, severe in its detail, save for some ornate and not entirely pleasing sculptures. You are interested in knowing how one of these giants—so typical of the new New York—are fabricated.
This young man—hardly a dozen years out of a big technical school—can tell you. He has supervised the job. Sometimes he has slept on it—in a narrow cot in the temporary draughting-house. He knows its every detail, as he knows the fingers of his hands.
"Just remember that we began by planning a railroad station in the basement with eight platform tracks for loading and unloading passengers."
"A railroad station?" you interrupt.
"Certainly," is his decisive reply. "Downstairs we will soon have the most important terminal of a brand new subway system crossing the Manhattan and the Williamsburgh bridges and reaching over Brooklyn like a giant gridiron."
He goes on to the next matter—this one settled.
"There was something more than that. We had to plant on that cellar a building towering forty stories in the air; its steel frame alone weighing twenty-six thousand tons—more than half the weight of the heaviest steel cantilever bridge in America—had to be firmly set."
The young engineer explains—in some detail. To find a foothold for this building was no sinecure. Tests with the diamond drill had shown that solid rock rested at a depth of 145 feet below street level at the south end of the plat. At the north end, the rock sloped away rapidly and so that part of the building rests upon compact sand. The rock topography of Manhattan island is uncertain. There are broad areas where solid gneiss crops close to the street level, others where it falls a hundred feet or more below water level. There is a hidden valley at Broadway and Reade street, a deep bowl farther up Broadway. Similarly, the north extremity of the Municipal Building rests upon the edge of still another granite bowl—the sub-surface of that same Collect Pond upon which the New York boys used to skate a century or more ago.
"That bothered some folks at first," laughs the engineer, "but we met it by sinking the caissons. We've more than a hundred piers down under this structure hanging on to Mother Earth. You don't realize the holding force of those piers," he continues. He turns quickly and points to a fourteen story building off over the trees of City Hall park. Out in one of the good-sized towns of the Middle West people would gasp a little at sight of it—in New York it is no longer even a tower.