Born at Ayr in 1808, James Fergusson was educated at the Royal High School, Edinburgh before attending a private school in Hounslow. Although he had no formal training as an architect, he was commissioned to design the iron dome built by Howard Grubb of Dublin for the observatory on the Calton Hill which was set up in October 1872. Although extra space was needed to accommodate the 22 inch refractor, he proposed that the new dome should not be raised more than fourteen inches in order to fit in with the dimensions of the building. While the shutter on the original wooden dome could only be opened to a width of several inches, the shutter on the iron dome could be opened to a width of several feet. image credit Wikimedia Commons.