THE NEW YORK POST-OFFICE, now being constructed at the southern point of City Hall Park, nearly opposite the Astor House, will be somewhat triangular in form, with a front of 279 feet toward the Park, two equal lateral façades of 262 ½ on Broadway and Park Row, and a front of 144 feet at the south-western extremity. The walls are to be of Dix Island granite, three stories besides basement and attic, the main cornice 80 feet above the sidewalk, and the crown of the central dome 160 feet. The windows are to be semicircular-headed throughout, the archivolts ornamented with voussoirs, and carried on projecting pilasters. The inside, which is to be devoted to the General Post-Office department and the United States Court, will have its appropriate appointments and corridors, while its exterior will be adorned with a profusion of classic pillars, balconies, balustrades, and other marks of genius. It will probably take several years to complete it, and cost as many millions. The post-office department of New York is a colossal enterprise. Over one hundred tons of mail matter are handled every twenty-four hours.