and material. The finest needles would break even with thin leather.

The needle having pierced through the material with the thread drawn tightly in the grooves on either side, and commencing to ascend, the thread is retained in the material by friction, and being lifted by the eye of the needle, assumes the form of a loop (a, Plate II., Fig. 25), which is then caught by a pointed instrument for the purpose of completing the stitch. If the needle is similarly constructed on both sides, equal sized loops will be formed on each side, and therefore the groove on that side of the needle where the loop is intended to be formed is made shorter than on the other (a b, Fig. 21), causing the thread to have a tendency to more readily leave the needle on this side, and to form the loop A and B, Fig. 25. Such needles as are made with grooves equally long on both sides more frequently make an imperfect loop, involving often an imperfect stitch.

The thread employed must be pliant, flexible, and soft. If stiff and hard thread is employed a bend (c, Fig. 25) is caused by the eye of the needle which prevents the formation of the loop. Sewing-machine thread must therefore not be stiff, thus excluding the use of wax, pitch, &c. Silk is better than cotton, and this again better than linen thread. Another requisite of good thread is evenness. If the thickness of the thread varies frequently and suddenly, the loops formed at such parts are generally imperfect. Machine thread must also be twisted more than common thread. Too great a twist, however, causes it to kink, which is also to be avoided. It is evident from the foregoing, that

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common sewing-thread cannot with advantage be employed. The finish alone of ordinary thread involves stiffness and a want of pliability.

Some time elapsed before the idea of forming the loop by a short upward motion of the needle was adopted. At first a semi-circular form was given to the needle just above the eye, and above this curve a second eye, both eyes being connected on the exterior periphery of the curve by a groove in which the thread ran, and by which the bend necessary for the formation of the loop was caused. The objections to this arrangement are evident. After the introduction of the straight needle, a kind of gripper was invented to catch the thread on that side of the needle where the loop was intended to be formed, but this arrangement has also been discarded.

As the first requisite in a sewing-machine is certainty in the formation of the loop, the height to which the needle must rise before the mechanism intended to catch the loop can commence its action is important. As, however, silk more easily forms a loop than cotton, and this again than linen thread, and as the shape of the loop should be adapted to the point by which it is intended to be caught, this height should also vary according to the circumstances. But this would involve a complication of the mechanism, and a distance of toin. has been adopted, generally, in. not being sufficient for thread of inferior quality.

After the formation of the loop the mechanism situated below the material, and which is intended to perfect the stitch, comes into play. The arrangement

of this varies according to the description of seam intended.

THE SINGLE-THREAD CHAIN-STITCH.

The needle with a hook point, first introduced by Thimonnier, a Frenchman, in 1830, for the purpose of forming the chain-stitch, has given rise to the most varied constructions of tambour-stitch machines. In the machine originally constructed by Thimonnier, the crochet needle works from above, while below the material the thread is conveyed from a spindle by means of the so-called thread carrier to the hook of the needle, which conveys it upwards as a loop passing the loop of the previously formed stitch. The chain is thus formed on the upper side of the material, while in the machines of a later construction it is on the lower side, the needle working from below and having a reciprocating motion, which not only dispenses with a special arrangement for propelling the material, but permits of the reel conveying the thread being a fixture, the thread being caught by the hook alone. The American Singer, a German by birth, introduced in 1854 a new principle, which is still in use. His machine has on the one side an eye-pointed needle, and a reciprocating hook or looper on the other. A closer examination of the motion of this hook shows that it consists of two motions, one perpendicular to the other. These two motions have also been given to two separate hooks working together, which at the same moment hold open the loop of the thread. Another inventor has dispensed with the horizontal vibratory motion, and introduced a perpendicular one; another causes the needle to vibrate,

making the hook a fixture; and a third causes the hook, which is affixed to a spring, to be pushed aside by the needle in its descent. Another has introduced an eyepointed needle on the one side, and a hook-pointed needle, by which the thread is caught and retained till the descent of the upper needle, on the lower side. Machines constructed on this system are still in use, one of which is delineated in Plate I.; but they are being gradually displaced by more practical ones, constructed on the system introduced by James Wilcox, in 1860. A machine of this description is represented in Plate II.

THE RECIPROCATING HOOK

consists merely of a conical point (b c, Fig. 21, Plate I.) with a triangular base, B. The point forms therefore a three-sided equilateral pyramid. The surface db lies horizontal, the surface d c perpendicular, so that the latter during the motion of the hook from left to right, and right to left, passes close to the needle. Fig. 19, A, represents the hook in its extreme position to the right, C, D, and E in its extreme left. In the first position it is about toin: distant from the needle, and is calculated to arrive at this position when the needle has reached its deepest point. The needle having risen about to1in., 18 so as to form the loop, the hook has moved so far from the right to the left that its point almost touches the needle, being about in. above the eye, or just at the widest point of the loop, Fig. 19, B. The needle rising still farther, the hook continues its motion to the left, catches the loop and holds it in that position, C, till the needle is withdrawn from the material and reaches its highest position. At this moment the material to be

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sewn is moved the distance of a stitch in a direction contrary to that of the hook and the needle, and the needle in its descent penetrates through into the loop E. To ensure this the hook, after reaching its extreme position on the left, moves in a direction perpendicular to its former one as indicated by the arrow, Fig. 21, A. The loop held by the hook becoming narrower towards the left, it is necessary for the needle to pass as close as possible behind the hook, the back of which, e, is therefore sometimes hollowed out (the hollow, ef, decreasing downwards) in order to allow the needle to come close to the foremost end of the loop. Directly the needle has caught the loop the hook is thrown back so quickly that the back part of it passes to 1⁄2 in. below the eye of the needle, as it would otherwise in passing so close to the needle fray and injure the thread. The backward motion of the hook must therefore be very rapid, and as it is of advantage that all the motions of a machine should be as slow and small as possible, it follows that the point of the needle should be as long, the hook as short, as possible. The needles for these machines are therefore generally made with a point of in. and more. The projecting point of the hook in., or, reckoning to the hollow before mentioned, in.

THE ROTATORY HOOK.

We have now to consider a rotatory hook, which catches the loop and holds it till the needle in making the succeeding stitch has descended and passed the loop. In this instance, also, the needle is calculated to have risen in. at the moment of the hook, which is

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