new states, the size of the U.S. Congress had grown accordingly and pushed the limits of the capacity of the Capitol. Under the guidance of the fourth Architect of the Capitol, Thomas U. Walter, extensions were built onto the north and south wings of the building. In the process, the new, longer building made the original Bulfinch dome appear aesthetically displeasing (and it had in any case been the object of much prior criticism). Congress, after lobbying by Walter and Montgomery C. Meigs (then Supervising Engineer), passed legislation to build a bigger dome in 1855. Second (current) dome The current cast iron dome of the United States Capitol is the second dome to sit above the building. Plans began in May 1854 to build a new cast-iron dome for the United States Capitol, sold on the aesthetics of a new dome, as well as the utility of a fire-proof one. Influenced by the great domes of Europe, Walter paid particular attention to the Pantheon of Paris, St Paul's Cathedral in London and St. Peter's Basilica in Rome, as well as the more recent Saint Isaac's Cathedral in Saint Petersburg, Russia, one of the first domes with an iron frame, by Auguste de Montferrand (1786–1858). William Allen, Historian of the Capitol, described Walter's first design as ... a tall, ellipsodial dome standing on a two-story drum with a ring of forty columns forming a peristyle surrounding the lower half of the drum. The upper part of the drum was enriched with decorated pilasters upholding a bracketed attic. Crowning the composition was a statue standing on a slender, columned tholus ... Walter drafted a drawing of the aforementioned design and displayed it in his office, where it drew the excited attention of members of Congress in 1854. A year later, on March 3, 1855, President Franklin Pierce signed off on the appropriation of $100,000 (equivalent to $ in ) to build the dome. Construction began after some practical changes to the original design (such as the reduction of the columns from 40 to 36) in September of that year with the removal of the dome raised by Charles Bulfinch. A unique scaffold was built inside the rotunda, designed to keep weight away from the weak center area of the floor, and a crane was set within to run on a steam-powered engine (fueled from the salvaged wood from the old dome). Over