The plumber John Scott of Edinburgh re-plated the roof in lead in 1743. Some minor additions were carried out in the following years. John Adam resurfaced the building in 1762 and James Playfair inserted a low window into the east facade in 1786. Overall, the Palace is built of sandstone and has the main entrance on the south front, flanked on each side by two Corinthian order pilasters. These are surmounted by a bracketed pediment unusual for its depth. The layout of Dalkeith Palace was unusual for the time in that the state apartment was located on the ground floor, which prevented the Great Dining Room from being placed in its customary position at the start of the state apartment. As such, the Great Dining Room was placed on the first floor, still suitable for important occasions and also serving as an anteroom to another apartment on the first floor. The 5th Duke of Buccleuch considered extensive rebuilding in 1831 and William Burn produced unexecuted designs in Jacobean style. More minor alterations were carried out, together with improvements to the surrounding estate including a new house and offices for the Duke's Chamberlain, and the construction, for the 5th Duke, of St Mary's Church as a private chapel by William Burn and David Bryce. The church contains one of only two water-powered organs in Scotland. Several well-known figures from English and Scottish history have been guests at the Palace in the intervening centuries. Bonnie Prince Charlie stayed two nights at Dalkeith in 1745, King George IV slept here during his visit to Edinburgh in 1822, in preference to Holyroodhouse Palace which was in a poor state, as did Queen Victoria in 1842. During World War II, Polish troops of the 3rd Flanders Rifle Brigade, part of the 1st Polish Armoured Division, were quartered on the third floor of Dalkeith Palace from 1942 onwards. Graffiti drawn by these troops is still visible on the third floor wallpaper of the Palace as of 2008. Dalkeith Palace has not been lived in by the Buccleuch family since 1914. In the 1970s and early 1980s, Dalkeith Palace was used as a research and development office by the computer firm International Computers Ltd. (ICL), which leased the Palace until 1983. Since 1985 it has been leased to the University of Wisconsin system for a study abroad programme. Approximately 60-80 students a semester live in the palace, where they also take classes from UK and US faculty members.