THE CAPITOL AT WASHINGTON.

Among the public buildings at Washington, the capital city of the nation, the first in architectural merit, and in point of interest, is the Capitol, which contains the halls of the national legislature, the supreme court room, &c., &c. This building (a view of which, as it will appear when the enlargement now in progress is completed, is given in the cut below) is situated on an eminence at the eastern part of the city, about seventy feet above tidewater, its main front looking toward the west. As it was before the commencement of the alterations and improvements now in progress, it consisted of a center building, with two wings, having a total length of three hundred and fifty-two feet, and a depth at the wings of one hundred and twenty-one feet. The central building contains a rotunda, ninety-six feet in diameter, and the same in hight, crowned by a magnificent dome which rises one hundred and forty-five feet from the ground. The wings, as they were, were each surmounted by a flat dome. The eastern front, which was intended for the main one, projects, including the steps, sixty-five feet, and is graced by a portico of twenty-two Corinthian columns, thirty feet in hight, forming a colonnade one hundred and sixty feet in length, presenting one of the most commanding fronts in the United States. The western front projects eighty-three feet, including the steps, and is embellished with a recessed portico of ten columns. This front, though not so imposing, in itself, as the eastern, commands the finest view anywhere to be had in Washington, overlooking all the central and western parts of the city, and all the principal public buildings. On the steps of the east front is a noble statue of Columbus, supporting a globe in his outstretched arm. In the interior of the western projection is the library of Congress, a part of which was burned in the winter of 1851-2. Before that event it contained over fifty thousand volumes. It has been rebuilt so as to be fire-proof.

On entering the rotunda, the first objects that strike the attention, are the paintings which adorn the walls. There are “The Declaration of Independence,” “The Surrender of Burgoyne,” “The Surrender of Cornwallis,” “Washington resigning his Commission,” “The Embarkation of the Pilgrims at Leyden,” “The Landing of Columbus,” “The Baptism of Pocohontas,” and “The Discovery of the Mississippi by De Soto.” Surrounding the rotunda, are a number of chambers, passages, committee-rooms, rooms for the president, members of the cabinet, &c. The senate-chamber is on the second floor of the north wing, of which it occupies about half, and is of a semicircular form, being seventy-five feet long, and forty-five high. A gallery for spectators, supported by iron or bronze pillars, surrounds the semicircle, and fronts the chair of the presiding officer, which stands in the middle of the chord of the semicircle. In the rear of the chair, and above it, is a gallery, supported by Ionic columns of the conglomerate or Potomac marble, in which sit the reporters, fronting the senators. The hall of representatives is on the second floor of the south wing, and is also semicircular, but much larger than the senate-chamber, being ninety-six feet long, and sixty high, and surrounded by twenty-four Corinthian columns of Potomac marble, with capitals of Italian marble. The galleries are similar in their arrangement to those of the senate-chamber. Over the chair of the speaker is a statue of Liberty, supported by an eagle with spread wings. In front of the chair, and immediately above the main entrance, is a figure representing History recording the events of the nation.

The enlargement of the Capitol, commenced in 1851, and now in progress, will, however, materially change and improve its appearance. It will comprehend two wings, two hundred and thirty-eight by one hundred and forty feet, which are to be surrounded on three sides by colonnades, and on the fourth side to communicate by corridors, forty-four feet long and fifty feet wide, with the main building. The whole will be seven hundred and fifty-one feet long, and will cover three and one-half acres, or more than one hundred and fifty-three thousand square feet. The architect of the new building has completed the design of a magnificent new dome for the center of the enlarged building, which is said to be a splendid conception of genius, and which is to take the place of the present dome, and thus perfect the symmetry and architectural beauty of the entire building when complete. It will be constructed entirely of cast iron, and will be on the foundation of the old dome. And if it at all meets the expectations formed of it, it will be a lasting monument of the skill and genius of the architect.

The whole cost of the building as it now stands, before the extension, was some two million dollars; but the improvement will cost several millions more. The original structure was commenced in 1793, and had not been completed when it was burned, by an act of vandalism, in 1814; and was not entirely finished till 1828. The grounds around the Capitol, embracing some thirty acres, and forming an oblong on three sides, and a semicircle on the west, are handsomely laid out, and planted with trees and shrubbery, presenting, during the spring and summer, a scene of great beauty. About the center of the grounds, on the eastern front, is a colossal statue of Washington, by Greenough. The material of the Capitol is a porous stone of a light yellow color, painted white. The enlargement is to be of marble.