In this way any alteration required can be made on the number of picks per inch given to cloth woven on a pressure or twilling harness, without distorting the pattern by varying the number of picks given to each card to suit the shotting. Neither is it necessary to have the same number of threads in each mail; the warp might be mailed 2’s and 3’s or 3’s and 4’s, but the more regular they are, the better. If the fineness of the cloth requires to be altered, it may be woven in the same harness without any alteration by varying the number of threads in the mails. For instance, a warp of ninety threads per inch mailed 3’s and one with 120 threads per inch mailed 4’s would work in the same harness. Similarly, the same set of cards would suit for making different widths of cloth by making the harness narrower in the cumber board and altering the mailing so as to keep the cloth the same set, or it may be made a finer set and not alter the mailing. In either case the pattern would be reduced in size.
Fig. 111 shows a portion of a pressure-harness mounting which is similar to that of the draw loom. It is mounted in the same manner as described for full harness, only that the warp must be divided by the number of threads to be drawn into each mail in order to find the quantity of harness required. The kinds of mails used are shown at A and B, Fig. 111; it does not do to have more than two threads drawn into each eye of the mail, as they are liable to twist round each other; two will separate easily, but a greater number will not. Ordinary full-harness mails answer very well for a two-thread harness. The mails are levelled in the same position as for full-harness work, viz. about 1-1/2 in. below the level of the back and front beams for hand-loom work, and a little lower for power looms. The lingoes are heavier than those required for a full harness; the weight depends upon the strength of the yarn and the number of threads in the mail; 10 to 12 to 1 lb. are used in power looms for linen damask with two threads in the mail, having about eighty to one hundred threads of warp per inch. For hand looms they are usually made of lead, thicker and shorter than the wire lingoes, and called ‘leads’; 11 to 15 per lb. suits for three- or four-thread harnesses. Light cotton work, such as muslin curtains, only requires lingoes of about sixty or seventy to 1 lb. for hand looms, but from twenty-five to thirty per lb. are used in power looms for two-thread harnesses.