By act of Congress, September 30, 1850, provision was made for the grand extension wings of the Capitol, to be built on such a plan as might be approved by the President. The plan of Thomas C. Walter was accepted by President Fillmore, June 10, 1851, and he was appointed architect of the Capitol to carry his plan into execution. Walter was the architect of Girard College, Philadelphia, and to him we owe the magnificent marble wings and iron dome of the Capitol. The dome cost one million one hundred thousand dollars. The wings cost six millions five hundred thousand dollars. The height of the interior of the dome of the Capitol from the floor of the rotunda is 180 feet and 3 inches. The height of the exterior from the floor of the basement story to the top of the crowning statue is 287 feet and 5 inches. The interior diameter is 97 feet. The exterior diameter of the drum is 108 feet. The greatest exterior diameter is 135 feet, 5 inches. The Capitol is 751 feet, 4 inches long, 31 feet longer than St. Peter’s in Rome, and 175 feet longer than St. Paul’s in London. The height of the interior of the dome of St. Peter’s is 330 feet. The height of the interior of the dome of St. Paul’s is 215 feet. The height of the exterior of St. Peter’s to the top of lantern is 432 feet. The height of the exterior of the dome of St. Paul’s is 215 feet. The ground actually covered by the Capitol is 153,112 square feet or 652 square feet more than 3 ½ acres. Of these the old building covered 61,201 square feet and the new wings with connecting corridors, 91,311 square feet. The dome of the Capitol is the highest structure in America. It is one hundred and eight feet higher than Washington Monument in Baltimore; sixty-eight feet higher than Bunker Hill Monument and twenty-three feet higher than the steeple of Trinity Church, New York. Mr. Walter was succeeded by Mr. Edward Clarke, the present architect of the Capitol. Thus far Mr. Clarke’s work has consisted chiefly in finishing and harmonizing the work of his varied and sometimes conflicting predecessors. Under his supervision the dome has been completed, and Thomas Crawford’s grand goddess of liberty, sixteen and one-half feet high, has ascended to its summit while he has wrought out in the interior the most harmonious room of the Capitol—the Congressional Library.