RIDING-HOUSES. 90'/ When a tower is used as a central support, it may have a staircase and balconies round it. To show how these galleries are placed in a parallelogram house, we shall here give a portion of the plan of the manege of Monaco, built for the king of Sardinia, by the late Architect Quarenghi, from a drawing given to us by him, in St. Petersburgh, in 1814. Fig. 1705 is half the ground plan, in which a is the inclined plane to the door 1705 O rrr-TTT .rT~iTC ' 1 XI^JJ Tti — trt by which the horses are taken in, and h the door for persons ; c is the platform, on which those who are to ride wait till the horses are brought up to them ; d, railings which open inwards ; and e, a staircase to the gallery over. One of the finest elevations that could be employed for a building of this kind would be that of a Grecian temple, with open porticoes at each end, and the spaces, between the window openings, arranged as pilasters. Quarenghi's elevation was as bad as could well be imagined: the roof was hipped (almost always a negative fault) at the two ends ; and pediments were raised on the sides, over the entrance doors for the horses. Quarenghi was any thing but an Architect of reason. 1939. The Construction of the Roofs of Riding-houses is the most expensive part of the edifice, as well as that requiring the most consideration from the Architect. The following communication on this subject, by Mr. Mallet, we present as particularly appropriate : — " For riding-houses, barns, large sheds, and other buildings requirino- roofs of considerable space, I conceive a roof I have some time since invented the best I have seen. It is constructed partly of cast and wrought iron, and partly of wood; and may be finally covered with slates, copper, zinc, or any other material usually so applied. Fig. 1 706 is a side view of one principal, or couple, of a roof for a riding-house, supposing it to be from thirty feet to eighty feet span. The main ribs, a a, are of cast iron, in section as in s ; and each is trussed by a round wrought-iron rod, b b, cottered into each end, and passed under the projection, or bracket, c. Thus, each principal rafter becomes trussed ; and, at the meeting of the rafters above, a vertical bar, d, descends, and meets the two inclined rods, e e, which proceed from the lower extremities of the principal ribs or rafters, z. In this manner the whole system is resolved into two triangles, d y z; in which the sides d y and z y are subjected to tensile, and the side d z to com- pressing forces. Thus, the whole principal, or couple, is firmly trussed. Fig. 1 707 is an enlarged view of the centre joint of the principal rafters ; a a are the ribs ; 6, the vertical tension bar ; and c, its cotter. The lap joint of the ribs is obvious at d c?; e e are the
