239 (#311) ############################################ PRINCIPLES AND PRACTICE this angle, but usually the twist will be below this, and in the case of lustres, etc., yarns, as low as possible. Generally speaking for worsted yarns the twist-angles will be Drafting twist 4° to gº Hosiery twist 8° to 16° Normal twist 16° to 24° To decide the lowest possible twist would require knowledge of frictional coefficients on each type of material, effects of twist on strength, weaving strength required, etc. etc. Here again is a large field for research. To decide the arrangement of fibres in the thread is really to select the type of spinning-frame or mule. For all frames direct the fibres away from the spindle during twisting and consequently the fibres have a given "inclination." This is clearly shown by making a warp with, say, 200 threads with fibres pointing in one direction and 200 threads with the fibres pointing in the other direction. The cloth made from this will show stripes just like a "chain-harrowed " grass field. . If in mule spinning the slivers were delivered and the carriage arrived at the extremity of its traverse without any twist being put into the yarn, and then the yarn were twisted, it is quite possible that the fibres would radiate out from the central core of the thread without any specific direction. But, again, this experiment has probably never been tried the insertion of the twist and the slight gain of the carriage in normal worsted- mule spinning will probably be quite sufficient, as a rule, to give a distinct inclination to the exterior fibres. Speed of spin also appears from the following record to affect the fibre arrangement, and it is possible the 239
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