At the doubling mill these threads are submitted to finishing processes, by which they may be polished and cleared and finally wound upon small bobbins or spools ready for the market, as seen in [Fig. 2].
A fair proportion of the very best yarns are utilised in the manufacture of lace and to imitate silk. Such yarns are usually passed through what is termed a "gassing" machine. In this process each thread is passed rapidly several times through a gas flame usually emanating from a burner of the Bunsen type. The passage of the thread through the flame is too rapid to allow of the burning down of the threads, but is not too quickly to prevent the loose oozy fibres, present more or less on the surface of all cotton yarns, to be burned away. This process is somewhat expensive, as it burns away perhaps 6 pounds weight of yarn in every 100 pounds. This, however, is obtained back again by the increased price of the yarn. It is a property of the cotton fibre that it can be made to imitate more or less either woollen, linen or silk goods, and since cotton is the cheapest fibre of the lot it follows that a considerable amount of cotton yarn is used in combination with these other fibres, in order to produce cheaper fabrics. Embroidery, crocheting and knitting cottons, and the hosiery trade absorb a large amount of the spun cotton yarn; the latter being doubled in most cases in order to fit it for the special work it is designed to do.
In a modern spinning mill the ground floor usually contains the openers, scutchers, drawing frames, carding engines and bobbin and fly-frames. The upper floors are usually covered by mules and other spinning frames.
Fig. 38.—Engine house, showing driving to various storeys.
In the last illustration ([Fig. 38]) is shown one of the latest engines built for special work such as is required in a cotton mill. The huge drum, on which rest the ropes and which can be clearly seen in the picture, is divided into grooves. A certain number of these is set apart for the special rooms. The strength of the rope is known and its transmitting power is also known. When the power required to drive say the first storey or second storey is calculated, it becomes an easy matter to distribute the ropes on the drum as required. This engine is now at work in the Bee-Hive Spinning Mill, Bolton.