length of each room is, therefore, 37 feet. In the northern arm are
placed the library, 23 feet by 27 feet; two computing rooms, 12 feet
by 23 feet each; side entrance halls, staircases, &c. The southern arm
contains the principal entrance, consisting of an arched colonnade of
four Tuscan columns, surrounded by a pediment. A broad flight of stone
steps leads to this colonnade; and through the entrance door beneath
it to the main central hall, 28 feet square, in which are placed (in
niches) the very beautiful electric clock and pendulum presented by
Erastus Corning, Esq. The center of this hall is occupied by a massive
pier of stone, 10 feet square, passing from the basement into the dome
above, and intended for the support of the great heliometer. Directly
opposite the entrance door is a large niche, in which it is proposed to
place the bust of the late Mr. Dudley. Immediately above this hall is
the equatorial room, a circular apartment, 22 feet 6 inches in diameter,
and 24 feet high, covered by a low conical roof, in which and in the
walls are the usual observing slits. The drum, or cylindrical portion,
of this room is divided into two parts--the lower one fixed, the upper,
revolving on cast-iron balls moving in grooved metal plates, can command
the entire horizon.

The building is in two stories--the upper of brick, with freestone
quoins, impost and window and door dressings, rests upon a rusticated
basement of freestone, six feet high. The style adopted is the modern
Italian, of which it is a very excellent specimen. The building has been
completed some time; but, in consequence of the size of the instruments
now procured being greater than that originally contemplated, sundry
alterations were required in the Transit and Meridian Circle rooms.
These consist of the semi-circular projections already mentioned, and
which, by varying the outlines of the building, will add greatly to its
beauty and picturesqueness.