The calculation of the size of the shed from given dimensions of the tappets and treadles forms a good example in leverage. Suppose the stroke of the tappet, or the distance through which it moves the treadle bowl (represented in Fig. 28), between the outer and inner circles is 3-1/2 inches. The treadle is 30 inches long, the treadle bowl being 25 inches from the treadle pin, and the healds connected 15 inches from the pin or fulcrum at N. Then the movement of the heald from its highest to its lowest level is equal to the distance moved through by the point N--_i.e._, 2·1 inches--for if the bowl moves 3-1/2 inches, the point N moves (3-1/2 × 15)/25 = 2·1 inches. This gives the size of the shed at the healds. Suppose the heald in question is 7 inches from the fell of the cloth, the shuttle passing through the shed 2 inches nearer to the cloth, then the size of the shed at the heald multiplied by 5 and divided by 7 gives its size at the point where the shuttle passes through, or (2·1 × 5) ÷ 7 = 1·5 inches. There is a slightly different shedding arrangement adopted in some looms, frequently so in Yorkshire, but rarely in Lancashire. This is the Bradford gear shown in Fig. 23. The tappets are placed outside of the loom, and the treadles are connected to the healds through jacks at the top of the loom. A leaf or projection on the tappet in this arrangement causes the heald to rise, not depressing it, as in the previously described arrangement. [Illustration: FIG. 23.--BRADFORD LOOM.] PICKING. Among cotton looms the over-pick or Blackburn pick is commonest. Attached to the tappet shaft are picking plates, one at each side of the loom. As the picking arrangement at one side is similar to that at the other, a single description applies to both.