John Ruskin pointed out, in The Stones of Venice, the great assistance which the science Of photography might render to the architect, in the accurate reproduction, within certain limits, of architectural details. It is curious that this Observation from so great an authority has not led more students of architecture to practice photography, and more photographers to pursue this branch of their science. It is probable, however, that the want of information, and the difficulty of Obtaining satisfactory instructions, has hindered many from attempting this class of subject. Many excellent papers have been read, and articles contributed to periodicals, but these could not be made available to the ordinary worker without much research. It is therefore hoped that this brief treatise, which presents practical information in a concise form, may supply a want.