 position is known, and thus the degree of twist on each of its faces may be ascertained, and the lines may then be marked off on the ends of the stone.
The theory of the skewed arch was given for the first time in the Transactions of the Royal Scottish Society of Arts for 1833 ; from which it was copied into the Civil Engineer and Architect's Journal for July 1840, which see. (For the history and various forms of the arch see Aneni-