This little work was originally written as part of a series of Elementary Lectures recommended by the Committee of the Oxford Architectural Society to be delivered to the junior Members of the Society, in the spring of 1849. They were con sidered useful and interesting by those who heard them, and as it was thought they might be equally so to others who had not the same Opportunity, the President, in the name of the Society, request ed the author to publish them. Mr. Winston's admirable Introduction to the Study of Painted Glass, formed part of the same series of Elementary Lectures, and'has also been published under the same auspices.