Mixing.—The raw material received into the bale-room is examined by dmwing samples from different parts of each bale, and is classified accordingly. This step is necessitated by the fact that the quality of cotton gathered at different periods of the picking season is subject to material variation. Errors of classification aud warehousing may produce a better or worse quality than the purchaser intended, or mistakes may be made in purthasing, from unfamiliarity with the needs of the establishment. These are sources of error to be guarded against. When the quality and magnitude of the mixing have been decided on, the classified stock is drawn upon ; the coverings are stripped from the bales, and the contents are passed in succession through the apertures in the floor to the room below, and spread upon the floor, in layers occupying a fixed area. Some times this space is railed off from the room. The " mixing " will be composed of as many layers as there are bales, these being taken in that order which will best enable their qualities to contribute to the end in view. When the mixing is completed, it is usual to test the result, by taking a vertical.section of the blend—raked from the face of the pile—, sufficiently large to manufacture into yarn ; this is carefully examined, and compared with a standard yarn, or with that from the last mixing. Should it be deficient in strength, cleanliness, or colour, a sufficiency is added of the raw material possessing the requisite quality. Sometimes the testing is repeated, especially when the quality is intended to be high class, and it is desirable to run no risk of deterioration; in other cases, the blend can be made so near the requirement, that it is not considered necessary. In low qualities, and admixtures of waste, the testing process is sometimes neglected; but in a well regulated establishment, it should never be omitted.
The satisfactory conditinn of the blend having been ascertained, it is ready for use. When required, it is carefully and evenly drawn down from the sides of the pile, by means of a rake ; this ensures a further intermixture of the qualities.
The component parts of the blend will necessarily differ according to the quality of yarn sought to be produced. Experience will enable cotton-spinners of average skill to prescribe mixings with great accuracy ; but there is nothing like uniformity among them in this respect, many affecting to keep the particulars secret. The following Table, however, very kindly furnished by John Butter worth, of Shaw, near Oldham, one of the most scientific and skilful spinners in Lancashire, shows, in a general manner, the adaptability of certain cottons for spinning different numbers of yarn, and their suitability for admixture with each other :— Several varieties n'ot named above would mix with one or other of the classes ; but special adaptatione must be left to the discretion of the spinner.
At this point, it may be well to explain the significance of the figures in the third column of the above Table. Yarns are alWays quoted by the pound, the price differing according to quality and
fineness. The latter is indicated by numbers, from Fs (one's) upwards ; the lhnit of fineness in the mercantile article is about 300's (three-hundred's). These numbers are .arrived at in the following manner :—In the early days of the trade, when yarns could not be spun with the regu larity that can be accomplished at present, uniformity was secured by reeling the yarn, and assorting the hanks according to weight. The circumference of the reel was lf yds., and the 80th revolution was indicated by a rap from a released spring, the length then wound being 120 yds., or 1 " lea." When 7 leas had been wound, they were tied together, forming 1 " hank," or 840 yds. The number of these hanks in 1 lb. indicates the fineness of the yarn, which is expressed thus — 4's, 12'8, 20's, 32's, 40's, 60's, &c., &c., to 300's. From the lowest Nos., it is customary to rise 1 hank at a time, up to 10's; thence steps of 2 hanks are generally taken, up to 24's ; then 4 hanks at a rise, up to 40's ; after this, the gradation, though sometimes 5, is generally 10 at a step. Any Nos. between these would be special, and would require to be spun to order.
Cotton yarns are always bought and sold by avoirdupois weight ; but, in ascertaining the counts or Nos., it is necessary to subdivide the pound into Troy grains, of which it contains 7000. The measure employed is as follows :— 54 in. = 1 thread (or circumference of reel). 4320 „ = 80 „ = 1 lea.
30240 „ = 560 „ = 7 „ = 1 hank, or 840 yds.
To ascertain the counts of a yarn, 7000 is divided by the weight (in grains) of one hank. It is customary, however, to take a proportionately less quantity, say 1, 2, or 3 leas, the dividend being 1000, 2000, or 3000 a,coordingly. The quotient is the number of hanks in 1 lb., hence the No. of the yarn.
Opening.—This process follows mixing. It is performed by the aid of various machines, according to the requirements or the preference of the spinner. The principal are the following :— The willow, the Crighton opener, the Porcupine, and Lord's opener.
The common, or Oldham, willow (Figs. 525 and 526) consists of a cylinder c, about 40 in. in diameter and 40 in. wide, mounted on a shaft, furnished with driving pulleys, and resting on bearings in the framework. Fitted on, and extending across, its periphery, are- several rows of teeth, or blunt spikes. A semicircular casing, in ternally furnished with two or three rows of spikes similar to the above, covers the upper part of this cylinder.
The lower portion is oovered with a wire grid, in two parts, hinged to gether. The back section of this is fixed to the frame, whilst the front part is balanced by weights, suspended from cords or straps, passed over pulleys at each side, and attached to the end of the grid, which is free to move up and down in an opening in front of the machine. An exhaust fan f is placed behind the fixed part of the grid.