The lower pivot of that arbor h is conical, and turns in a socket fixed in the floor. The great wheel L rests on the collet i, furnished with its 4 iron pins, for securing the connection. Above the wheel an iron washer is laid, and the whole is fixed by a double wedge, which enters into the mortise l, [fig. 620.]
[Fig. 621.] exhibits a ground-plan view of all this assemblage of parts, to explain the structure of the machine. Every thing that stands above the upper summer-bar has been suppressed in this representation. Here we see the table c c; the upper summer m; the one wheel-plate l, the other having been removed to shew that the endless cord does not cross; the two large wheels L L, present in each machine, the crank bar N, seen separate in [fig. 622], which serves for turning the wheel L. This bar is formed of 3 iron plates n, o; p, q; and q, r; ([fig. 622.]) The first is bent round at the point n, to embrace the stud s; the second p q, is of the same breadth and thickness as the first; and the third, is adjusted to the latter with a hinge joint, at the point q, where they are both turned into a circular form, to embrace the crank M. When all these pieces are connected, they are fixed at the proper lengths by the buckles or square rings t t t, which embrace these pieces, as is shown in [fig. 622.]
The stud s, seen in [fig. 622.], is fixed to the point v by a wedge-key upon the arm P, represented separately, and in perspective, in [fig. 623.] The labourer seizing the two upright pegs or handles x x; by the alternate forward and backward motion of his arm, he communicates the same motion to the crank rod, which transmits it to the crank of the arbor M, and impresses on that arbor, and the wheel which it bears, a rotatory movement.