worn. Both right-angled and cylindrical carriers are very liable to work loose.

The needle is attached to the carrier by a screw in various manners. In Plate IV., Figs. 1 and 2, it is shown fastened in a groove running parallel to the axis of the carrier by the head of a square bolt passing through the carrier, and tightened by a screw and nut. In Fig. 1, Plate VI., it is fastened by a wedge, p, to which a screw is attached. In larger carriers the needle is fastened in a perpendicular bore provided with a set screw, o, Plate V., Fig. 1. In round carriers, or such as have their lower extremity round, a nut, B, Plate II., Fig. 12, with a conical bore, compresses the cone-shaped slotted end of the carrier on the needle.

It is absolutely necessary that the needle should be perfectly parallel to the axis of the carrier, and should this not be the case when fitted, it must be bent in the right direction, and the shanks of the needles are therefore generally left untempered.

The needle carrier must be constructed as light as possible, consistent with the necessary solidity, but owing to the friction even then attendant on its use, the needle has been attached to the end of a lever, 6 to 8 in. in length, moving in a perpendicular plane. This is in fact the first arrangement, the needle carrier having been first introduced in 1846. It is chiefly employed for light work on account of the weakness of the needles, owing to the curved form which must be given them corresponding to the arc described by them. As this curve must exactly correspond to that described by the end of the lever, this description of needle is generally pro

vided with a flat shank to prevent the needle from turning.

Motion is communicated to the needle by means of a shaft, with either a crank worked by hand, or a flywheel connected by driving bands with a treadle. This shaft is called the main or driving shaft, and is always horizontal. Its position varies, being in some machines above, in others below the sewing plate; it is also placed sometimes parallel, sometimes perpendicular, to the axis of the machine. The means of transmission of motion from the main shaft to the needle also vary, a crank being generally sufficient, otherwise an eccentric slot is employed.

There are therefore eight various combinations which will be described below.

The main shaft lies above the sewing plate, parallel with the axis of the machine, and motion is transmitted by means of a crank. Instead of an ordinary crank a round plate, or disc, is generally affixed to the front end of the main shaft, having a projecting stud passing through one end of a connecting rod, the other end of which is attached to the needle carrier. As it is generally advantageous to cause the needle to dwell at its highest and lowest points of motion, the connecting rod is usually made short in proportion to the length of the crank-it is frequently not more than in. longer than the latter.

The main shaft lies above the sewing plate, parallel to the axis of the machine, and motion is transmitted by means of an eccentric slot. This arrangement is similar to the one just described, except that the disc is provided on its front surface with an eccentric slot in which a

friction roller, attached by a pin to the needle carrier, works. (See machine shown in Plate I.) In this instance the slot revolves while the pin has the ascending and descending motion. In Plate IV. a machine is shown in which the roller is attached to a pin in the disc, while the needle carrier itself is slotted.

The main shaft lies above the sewing plate perpendicular to the axis of the machine and motion is transmitted by a crank. It is evident that in this arrangement the main shaft must be placed in the rear of the bracket, as its transmission gearing would otherwise diminish the space for the passage of the material to be sewn. This position of the main shaft also requires the circular motion of the crank changed, by a connecting rod, into a rectilinear one to be transmitted to the needle carrier by a lever. If the guide of the connecting rod is perpendicular the lever must be straight, if diagonal or horizontal, a bent lever must be employed. In the first case, Plate VII., Fig. 24, the shaft would be placed but a slight distance above the sewing plate; in fact, it would be most advantageous in machines having the main shaft perpendicular to their axis to place it below the sewing plate. In the second case the back of the machine would have to be disproportionately lengthened, and this arrangement is therefore but seldom employed.

The main shaft lies above the sewing plate perpendicular to the axis of the machine, and motion is transmitted by an eccentric slot. This slot is constructed in the plate attached to the front end of the main shaft, and the transmission roller forms the end of a lever communicating motion to the needle carrier. The arrangements

vary slightly, according as a straight or bent lever is employed, but the principle remains the same.

The main shaft lies below the sewing plate, parallel to the axis of the machine, and motion is transmitted by a crank. The crank is affixed to the back end of the shaft, and gives motion by means of a universal joint to a connecting rod moving in a perpendicular plane, to the other end of which the end of a horizontal lever is attached by which the motion is transmitted to the needle carrier. See Fig. 29, also machine shown in Plate II.

The main shaft lies below the sewing plate, parallel to the axis of the machine, motion being transmitted by means of an eccentric groove. (See machine shown in Plate V.) The groove is in this instance on the exterior of a cylinder attached to the main shaft, and the roller transmitting the motion to a bent lever has a reciprocating motion, almost rectilinear, horizontal to the surface of the cylinder, Plate VII., Fig. 30. The path of the roller is a flat curve, the plane of which is perpendicular, parallel to the axis of the shaft, and touching the cylinder in a straight line from which the curve described deviates but slightly. To reduce this deviation as much as possible, the lever arm to which the roller is attached, as also the diameter of the cylinder, are made as large as possible, and the curve described by the roller is so arranged that its extremities are just the same height above the point of contact as its centre is below.

The main shaft lies below the sewing plate, perpendicular to the axis of the machine, and motion is transmitted by a

crank. The principle of this construction, Figs. 31 and 32, does not differ from that shown in Figs. 24 and 25. The proportions of the parts alone vary.

The main shaft lies below the sewing plate, perpendicular to the machine axis, and motion is transmitted by an eccentric groove. This arrangement, Figs. 33 and 34, also corresponds with that shown in Figs. 27 and 28, except that the straight lever shown in Fig. 27 is replaced in Fig. 33 by a lever bent at an obtuse angle, and that the proportions of the various parts differ. Assuming the main shaft in the front part of the machine, the lever takes the form of ➡. By giving the roller the rotating, the groove the reciprocating, motion, and making the groove rectilinear, we obtain the form of arrangement shown in Plate III.

In most of these arrangements motion is transferred to the needle carrier by a lever which is attached in various manners. Either the end of the lever has a slot, in which a stud attached to the needle carrier travels, or a short connecting rod is employed. This arrangement with levers alone makes it possible to dispense with the needle carrier, and to employ curved needles. As, however, when curved needles are made use of, the fulcrum of the lever must be but slightly above the sewing plate, a straight lever is inadmissible. In Plate VII. a machine of this description is shown according to the plan of Fig. 31.

THE TRANSMISSION OF MOTION TO THE LOWER MECHANISM.

The arrangements below the sewing plate vary much in different machines. They may be thus classified: Those with a rotating motion, including the revolving