802 SEWING MACHINE analogous manner. The upper thread e is car- ried by an eye-pointed needle (35, tig. 7), and a loop of it is thrust through the fabric by the needle; the loop is then entered by the point a of the rotating hook. The lower thread z is carried upon a thin metallic bobbin lying in the concavity of the hook, where it is held by a concave ring (not shown). The bobbin has no axis, so that a loop of thread can be freely passed around it. The loop of the upper thread is enlarged by the hook (fig. 8), and carried forward and around the bobbin containing the it X Fio. 9. lower thread, as in fig. 9, and being drawn up as in fig. 8, in the process of enlarging the next loop, interlocks with it, and the point of interlocking is drawn into the fabric and forms a stitch. Wheeler and Wilson have made an- other form of lock-stitch machine, the inven- tion of Mr. James A. House, which also em- ploys a rotary hook, but completes a stitch at each revolution, drawing it up by a separate arm known as an independent " take-up." An eccentric attachment causes the hook to rotate more rapidly during one part of its revolution, and there is a " pad " or projection of steel on the revolving hook, or rather the wheel that carries it, by which the under thread is held firmly during a short period, which assists in the completion of the stitch. This produces the "tension," which can be regalated while the machine is in motion, and differs there- fore from that just described in the family ma- chine, which depends upon the friction of the revolving hook against the bobbin. The new machine is made of different sizes, some very large and strong, for heavy manufacturing work. The needle, being straight, is capable of penetrating stout leather. The medium sizes may also be used for tailoring as well as light domestic sewing. The single-thread chain or crochet stitch is shown in fig. 10. It is formed by passing a thread through the fab- ric and making a loop, then making a second Fio. 10. Crochet Stitch. loop and passing it through the first, and again making a third and passing it through tlio second, and so on. This may be done with an eye-pointed needle and a reciprocating or vibrating hook, but does not form a very du- rable stitch, from its tendency to ravel. If, however, each loop is twisted, as shown in fig. FIG. 11. Twisted Loop Stitch. 11, ravelling is difficult, and when the work is well done not liable to occur, except by de- sign. A mechanism for producing such a twist was patented by J. E. A. Gibbs of Millpoint, Va. A rotating hook causes the relations of the threads on each side to become changed toward each other. The different parts of the hook are shown in fig. 12, in which 18 is the shank, 19 the point of the hook, 20 the " cast- off," and 21 the heel; K K is the shield for protecting the thread from oil. In fig. 13 the needle, having descended to the lowest point, carrying down the thread, has just begun to ascend; and a loop is thrown oil on the back Fio. 12. Fio. 18. side of the needle just in time for the point of the hook to enter it. As the needle rises, the hook, moving in the direction of the arrow, passes into the loop, drawing it down and spreading it. As the hook advances from this point the loop begins to twist ; thread No. 1, 20 Fio. H. Fio. 15. fig. 14, moving to the right, slides off the shoulder at the centre of the hook and falls down to the shank, near the shield K, while the heel, 21, catches the back side of the loop 2, and swinging it around passes into the loop which is being reversed. As the hook still advances and the heel passes further into the loop, thread No. 2 slides into the angle at the centre of the hook, as seen in fig. 15. The loop is now completely reversed, thread No. 2 being on this side of the needle, and
