[JJO COTTAGE, FARM, AND VILLA ARCHITECTURE. altogether counteracts the expression of tension ; and whenever an ornament cither is, or appears to be, at variance with the expression of the use of the part to which it is applied, it becomes a deformity. All the struts, or pressure pieces, of an iron roof may be ornamented without any offence against the principle of fitness ; and this Mr. Mallet has done very judiciously, iu the main ribs and pendent struts of fig. 1715. 1942. A Cast-iron Hoof for a Riding-house may he formed on the same principle as one designed by the late Mr. Tredgold, for co- vering the corn market at Norwich. Fig. 1716 is a section showing the half of one of the cast- iron rafters of this roof, in the form of a Gothic arch, with the spandril filled in with tracery. The span is fifty-four feet ; the columns, a, from which the cast-iron arches spring, are of stone; the walls of brick, and the roof covered with slates, nailed to boards, supported by wooden purlins and rafters. The purlins, shown at b, are eight inches and a quarter by five inches and a quar- ter, and the rafters are four inches and a half by two inches and a half. This section was kindly furnished to us by our much esteemed friend Mr. Thorold, who, having been for many years on intimate terms with Mr. Tred- gold, possesses his work- ing-plans and calcula- tions for this and for various other great works. It is evident that a roof of this de- scription, on a riding- house, would have a very grand and rich effect : there might be a row of Gothic win- dows in each of the side walls, and one large window in each gable reaching from the ground to the roof; the lower parts of which windows might serve as doors. Above the doors, in the inside, there might be galleries for spectators. 1943. TJie Framing of a Timber Roof for a Riding-house of great Width, and where, as in Russia and America, timber is abundant, might be constructed on the principle of that of the Grande Salle d'Exercice at Moscow, one half of a single truss of which is shown in fig. 1717. This magnificent exercising-house is 150 feet (French) broad, and 502 feet (French) long; the walls are 40 feet high, and 8 feet thick above the ground; and their foundations, which are 12 feet under ground, are 14 feet thick. The building was constructed in 1*17, including the making and burning of the bricks for the walls, and the cutting down of the timber for the scaffolding. It was begun and finished in the short space of five months, in order to enable the Em- peror Alexander to exercise his troops in it, during the winter of 1817-18 which the
