To start the machine, the footboard is pressed down, the slide consequently lifted and held in position by a hook which catches on the framework. By an inclined collar J, on the centre of the lever H (Fig. 11), the friction pulley and plate are pressed into contact and the machine is in motion. When an end breaks, the hair-pin drops between the nip rollers, pressing the loose one away from the other, therefore by means of the upright lever already referred to knocking off the catch H (Fig. 10). As soon as this is done the slide drops, and with it the lever O. The inclined collar relieves the pressure on the friction plate and the machine stops. The attendant pieces the broken end which is thus brought under his or her notice. Beam warping machines are of various sizes, the most common being for 504 bobbins, the width being 9/8ths, or 54 inches between the flanges of beam. Other widths, of course, are in use, from 44 to 108 inches. The waste of yarn, in the preparatory processes, indeed in all departments of mill work, is extremely important, and should be kept at as low a percentage as possible. At the winding frame the total waste should be 1 to 1-1/4 per cent., varying with the count and quality of yarn, and the total waste of warp yarn throughout the mill should not exceed 1-1/2 per cent. at the most. For the purpose of measuring the length of yarn on the beam, each warping frame is supplied with a roller half-a-yard in circumference, round which the yarn passes; on the end of this roller is a worm driving a worm wheel B, of 54 teeth; on the stud carrying B is a second worm C, driving a worm wheel of 132 teeth. The worm only takes one tooth at each revolution, therefore a complete revolution of the first worm wheel represents a length of 27 yards having passed the measuring roller; this is equal to one tooth only on the second wheel B; therefore, a complete revolution of the latter means 3564 yards--technically called a wrap--1/2 × (54 × 132)/(1 × 1) = 3564. If a warp contains 4 wraps and 7 teeth, it is 14,445 yards long - 4 × 3564 + (7 × 27). For other warping calculations see Chapter IX. The faults in beams are principally, bad, or no piecings, soft places caused by fine threads, or ends unevenly distributed in the combs, or by crooked flanges. Where dhooties and other striped cloths are made, the warper has to be provided with a sheet showing how the coloured yarn is “laid in” at the side. This will be described under the heading of Dhooties. Where possible, all the coloured yarn is placed on one beam of the set, leaving the other beams all “grey,” as the undyed yarn is termed. In any case of warping two counts of yarn on one beam, whether coloured or grey, allowance must be made for the different diameters of the threads. SECTIONAL WARPING. [Illustration: PLATE III.--SECTIONAL WARPING FRAME. _To face pp. 28 and 29._]