The width of the courses of ashlers must, therefore, be made equal exactly to a certain number of courses of bricks with the intervening mortar, and the brick-work must be executed with such care, that this number of courses may be everywhere of the same width in the whole height of the wall. In every course of ashler there must be solid stones laid quite, or nearly quite, across the width of the wall to form a _bond_ to the stone facing, and all the stones of the ashler must be fixed with iron cramps to one another and to these bond-stones. But, however carefully a faced wall may be executed, it is never so firm or durable as one built entirely of either material; indeed, if well executed, of good materials, and of competent thickness in proportion to its height, a brick wall is the most durable, light, and efficient structure that can be erected. When stone is to be cut into cornices, mouldings, &c., the blocks having been sawed, the ends, top and bottom, are worked very true and parallel, or perpendicular to each other, and one edge or _arris_ cut to a perfectly straight line; a thin wooden mould of the section of the cornice is then applied to each end, and the profile of the mouldings marked out on the stone. The workman being guided by this figure, cuts away the stone down to the general surface of the mouldings, and then proceeds to get the flat fillets of the mouldings perfectly straight and true by the rule; these again guide him in working the curved mouldings, such as _ovolos_, _cavettos_, _cyma rectas_, and _ogees_; when these are cut nearly to their profile, and perfectly straight on the _bed_ line, they are finished off by being rubbed down smooth by thin long straight-edges of stone. Foliage and carved work is executed by a better kind of workman, possessing some of the taste of an artist, and he works on the same general principles as a sculptor when executing a statue; it would be foreign to our present object, therefore, to dwell on this branch of the mason’s art. It often, or even most commonly occurs, that the distance between two columns of a portico, is of greater length than a stone can be obtained, and if the architrave, or that part of the _entablature_ immediately over the capitals of the columns, be looked at attentively, a stone will be perceived between the columns apparently unsupported, for neither end rests on the column, and the joints of those ends are upright, not presenting any character of a voussoir-stone or arch. The contrivance by which such an architrave stone is supported deserves to be described. [Illustration] The stone in question has a projecting part, wrought at each end, of the form shown in the annexed figure; this projection is received into a corresponding cavity, cut in the end of the stone supported by the column, and the joint is thus really an arched or wedge-shaped one, though the bevel line is concealed, and the two stones, when put together, present only a vertical joint.