(378) A glance at Fig. 188 will show that between the ring rail and the nip of the front rollers there is about ten inches of yarn, which, when it is being twisted, is held by the traveller and the rollers, and tends to fly outwards and assume a curved course, which from its shape is called a “balloon.” This is caused by the centrifugal action of the yarn and the resistance of the atmosphere, and leads, unless checked, to a serious loss of twist. In addition to this as the distance between the centres of the spindles is only 2 or 3 inches ordinarily, it is obvious that if this tendency is unchecked contiguous ends will come into contact and frequent breakages occur. The author was informed by Mr. Bernhardt that a careful trial made by him established the fact that, where the balloon is unchecked and allowed to attain its greatest size, the breakages are six and a half times as numerous as when its size is in some way limited. There are two methods of doing this, one by surrounding the spindle with a guard which prevents the balloon attaining more than a certain fixed maximum diameter, and the other by so adjusting the position of the thread board that the distance between the wire eye and the traveller is such that not more than a certain sized balloon can be formed. It is a well known fact that a balloon is absolutely essential to good spinning, as its centrifugal action enables a lighter traveller to be used, and the drag upon the yarn is thus reduced to a minimum. The use of a heavy traveller undoubtedly will check ballooning, but the yarn will suffer, and therefore a well formed but not excessive balloon is of advantage. Mr. Brooks employs a plate (=L=, Fig. 188) pierced with a number of holes and mounted on pokers, which gradually rise higher as the bobbin fills, so that the balloon is checked by the hole in the plate. Other makers, such as Messrs. Platt Brothers and Co., Howard and Bullough, and Dobson and Barlow, employ forked wire guards which serve the same purpose as the plates referred to. Fig. 194 represents the appliance used by Mr. Bernhardt, which is very effective and is worth attention. Instead of depending upon a guard of the character referred to, the ballooning is checked by maintaining a defined distance between the guide eyes and the ring rail. It is clear that as the latter rises, if the guides are stationary, there will be a greater tendency to balloon when the rail is at its lowest position than when at its highest. More than that, the attainment of the full diameter of the cop is followed by more ballooning than when the building is just beginning, and it is therefore advisable to slightly shorten the distance between the guide and the point of the spindle. The guides are in this case mounted on a rod borne by and attached to vertical pokers =A=. The vertical position of =A= is determined by the cam =C=, which is slowly rotated as building proceeds. The shape of =C= is such that when spinning begins, the guide eye =A= is about an inch above the nose of the bobbin, but gradually falls until within 3/8 inch of the same point, after which it slowly rises until the relative positions at the commencement and finish are as indicated by the dotted and full lines. The rise begins as soon as the cop is formed of full diameter, and one important feature in this invention is that the vertical reciprocations of the guide eyes are independent of, less than, although simultaneous with, those of the ring rail. It is certainly remarkable how effective this contrivance is in checking ballooning, and this without submitting the yarn to any injurious rubbing action. The size of the balloon is accurately checked, while at the same time it is as large as can be permitted under the existing conditions. The inventor stated that the effect of this arrangement is that a bobbin of 6 inch lift can be employed, where in other cases not more than a 5 inch bobbin could be used. The extra length of yarn so wound on is of great service in subsequent processes, giving rise to other advantages which are well known.