Wooden (oak) model of an arched bridge, the arch of which consists of six timbers bound together by iron straps and rods. Only half of the bridge is shown in detail. The second, presumably symetrical, half of the arch is represented by two curved boards. The roadway is also shown only in outline. Only the upper and lower timbers extend the full length of the half arch. The remaining four are of various lengths, cut to fit the bottom timber to which they are fastened by iron straps. Cross timbers held together by iron tie-rods hold together the top and bottom timbers. (Robert P. Multhauf, "Catalogue of Instruments and Models," 1961).