Sewing Machines

Allan B. Wilson also worked without knowledge of previous efforts. In 1849 he devised the rotary hook and bobbin combina tion, forming the special feature of the Wheeler and Wilson machine. Wilson obtained a patent for his machine, which in cluded the important and effective four-motion feed for moving the work after every stitch, in Nov. 185o. In Feb. 1851 William 0. Grover, a tailor, of Boston, patented his double chain-stitch action, which formed the basis of the Grover and Baker machine. In 1856 James A. E. Gibbs (1829-1902), a Virginia farmer, devised the chain-stitch machine, improved subsequently by J. Willcox and now known as the Willcox and Gibbs. These together —all American inventions—form the types of the various ma chines now in common use. Thousands of patents have been issued in the United States and Europe, covering improvements in the sewing machine ; but, although its efficiency and usefulness have been greatly increased by numerous accessories and attach ments, the main principles have not been affected thereby.

Chain Stitch.

In machine sewing three varieties of stitch are made—(1) the simple chain or tambour stitch, (2) the double chain stitch and (3) the lock stitch. In the first the machine works with a single thread, the other forms use two, an upper and an under.

The Modern Lock Stitch.

The lock stitch is that made by all ordinary two-thread sewing machines, and is a stitch peculiar to machine sewing. It consists of an upper or needle thread and an under thread locked together in the material which is being stitched ; the lock being formed by passing the upper around the lower thread and tightening them together in the middle of the fabric, as shown in fig. a. In fig. 2 the needle thread is shown as a thick black line and the under thread white, the fabric being stippled in order that each may be readily recognized. It shows the head of a lock stitch machine, rotary hook. The loop of needle thread has been taken by the point of • the hook and is being passed round the bobbin case containing the bobbin of under thread, sufficient enlargement of the loop having been per mitted by the descent of the thread take-up lever.

In fig. 3 is shown the head of a vibrating shuttle machine. The shuttle, containing the bobbin of under thread, has fully entered the loop of needle thread, sufficient enlargement of the loop hav ing been permitted by the descent of the thread take-up lever. The shuttle travels to and fro in a carrier to which it is not fastened, but by which it is held in position. During the forward movement of the shuttle, the loop of needle thread slips between the shuttle and the carrier, then passes out between the heel of the shuttle and the rear part of the carrier. The shuttle thread is thus

enclosed in the loop of needle thread and both threads are then drawn up by the action of the thread take-up lever.

There are over 2.000 varieties of modern sewing machines designed for stitching processes in the great sewing industries mak ing up clothing, boots and shoes, corsets, hats, hosiery, etc. There are machines specially designed for sewing regular or fancy shank buttons on shoes; for sewing sweat leathers into stiff felt, soft felt or straw hats ; for trimming, scalloping and over-edging lace curtains; for sewing silk initials, monograms or floral designs upon material at one operation. There is a seven needle machine for making seven parallel rows of fine double chain stitching simul taneously. This machine is fitted with seven needles and seven loopers, and its capacity is over 20,000 stitches per minute.

The increasing use of electricity for domestic purposes has had its effect on the sewing machines. To adapt existing machines to electric operation, small motors are provided. There are also available sewing machines of various types with the motor incor porated in the body of the machine. Foot control or knee control is used. A small electric lamp directly over the work is often furnished.

SEX.

Among the higher animals each individual is either male or female. In them maleness is the state associated with the production of spermatozoa; femaleness that associated with the elaboration of ova. A male is an individual that is efficiently equipped for the elaboration of functional spermatozoa and for the conveyance of these towards the site of fertilisation; a female one efficiently equipped for the elaboration of functional ova, for the conveyance of these to the site of fertilisation, and often, as in the mammals, for the prenatal care of the embryo and foetus and for the nurture of the offspring. In certain groups maleness and femaleness are exhibited by one and the same individual either concurrently or in succession: such groups are hermaphrodites.

Where the sexes are distinct, male is to be distinguished from female by differences in (I) the form and structure of the gonads or reproductive organs, those of the male being testes, those of the female, ovaries; (2) the accessory sexual apparatus of ducts and associated glands concerned with the transit of the products of the gonads; (3) the external organs of reproduction, and (4) certain skeletal, cutaneous and other less definite physiological, biochemical and psychological characters.