MILLS, KILNS, MALT-HOUSES, KTC. 587 Fig. 1120 is an elevation of the east side of the structure, in which t is the com- mencement of the lever. Fig. 1122 is an elevation of the north side, showing the front of the sails, the armsi of which pass through mortises in the end of the wind-shaft, and are bolted to pro- jecting arms. The sails are clothed and unclothed by a line fastened to the upper corner of the canvass, passing over a pulley, and down the side of the arm to the bottom, where it is fastened. By these means, the canvass can be spread out at the end nearest the axis from below, in the same manner as a common window-curtain ; the lower part is spread out by hand, and tied. When the mill is not at work, the canvass is gathered up in a roU over the arm. There are patent windmiU saUs now in use, in which a number of flaps or shutters of thin wood supply the place of canvass. They can all be moved from below, so as to present their edges to the wind when the mill is not at work. The computed power of a windmill, with four sails, measuring 66 feet French from the ex- tremity of one sail to that of the opposite one, and 6 feet wide, or a little more, is, that it will raise 1000 French lbs. 218 feet in a minute, and is capable of working eight hours in a day upon an average. This is equivalent to the work of 34 men ; 25 square feet of canvass performing about the daily work of one man. Fig. 1 1 23 is an elevation of the west side, in which t is the commencement of the lever, which serves for turning the sails to the ^v^nd. Fig. 1124 is a transverse section of fig. 1118, from C to D, showing the framing of the mill. The corner or principal posts are 8 inches by 8 inches ; the principal quarters and braces are 4 inches by 4 inches ; and the common quarters are 4 inches by 3 inches. The clear height of the ground floor is 9 feet 8 inches ; the clear height of the stone floor story is 7 feet 6 inches ; that of the bin floor story 6 feet 8 inches j and
