PREFACE. The Council of the Royal College of Science, Dublin, having assented to a course of lectures to be delivered during the evenings of 1870-71, on Building and Ornamental Stones, I commenced the necessary preparation. Circumstances, however, occurred to prevent the delivery of the course; but while arranging the materials, the subject seemed to grow in interest, and ultimately developed into the form in which it is presented to the reader. During the progress of my investigations I made the discovery that there is no work in our lan guage especially devoted to the subject itself; a discovery which is the ground on which I now come before the public. Building and Ornamental Stones are, it is true, to a certain extent described in many of the works on masonry, architecture, and engineering, but not in a complete manner, nor with much attempt at scientific arrangement. The