Though we have evidence that concrete was used by the Ancient Romans in the foundations of some of their structures and even in the formation of their roads --such as the Appian-Way, and though we find it used in the foundations of the feudal castles of the Norman Barons of England, still it has not been introduced into the general practice of architure until quite a modern date, and even at the present time is not widely appreciated in this country as a material of so much importance in foundations. The side walls are laid up in a character of workmanship styled "rough-hammered work" the stone required to be of

sound and durable quality and laid in a manner to render the work water-tight. Though attention is given in some degree to insure a proper bond to the wall, yet the point more particularly attended to, is to make it compact and impervious to water. The bonding of the wall is not by any means disregarded, in all situations where it is required, yet the position of the work generally, where it is in excavation below the natural surface of the ground, renders such precaution of less importance than that of making it compact. The mortar used in these side walls is formed by mixing clean sharp sand with hydraulic lime, using the proportions of three parts of the sand to one of the lime ; and these are thoroughly mixed and incorporated before they are wet ; when this mixture is wet and thoroughly worked, it is used immediately and always kept properly tempered so as to render it plastic, and to prevent any disposition to become hardened before it is in the wall. After the side