David MacGibbon and Thomas Ross. The Ecclesiastical Architecture of Scotland from the Earliest Christian Times to the Seventeenth Century. 3 vols. Edinburgh: David Douglas, 1896-1897.

The Ecclesiastical Architecture of Scotland by the architects David MacGibbon(1831-1902) and Thomas Ross (1839-1930) was an extension of their work on the domestic architecture of Scotland. The authors sought to document all extant churches from the early medieval period through the Reformation and arranged the text chronologically. Each entry includes a basic description of the architectural fabric, often including measured drawings and occasionally an historical account associated with the churches. For anyone interested in early Scottish architecture, it is an excellent starting point.  Below are the drawings for the Chapel of St. Margaret, Castle Rock, Edinburgh.