The cotton is seldom unpacked until it arrives at the mill, the purchases being all managed by samples. When it is unpacked, the first thing to be done is the sorting, and in this much care and skill are required; for the different bags furnish different qualities of cotton, and it is necessary to produce yarn of uniform quality at the cheapest rate. In order, therefore, to equalize the different qualities, the contents of all the bags are mixed together in the following manner. A space being cleared and marked out on the floor, the cotton contained in the first bag is scattered over this space, so as exactly to cover it; the contents of the second bag are in like manner spread over the first, and the cotton in all the other bags is disposed in a similar manner; men and boys tread down the heap, which is called a _bing_ or _bunker_, until at length it rises up in shape and dimensions very much like a haystack. Whenever a supply of cotton is taken from the bing it is torn down with a rake from top to bottom, by which means it is evident the contents of the different bags are collected together in a mass of uniform quality and colour. In mixing different qualities of cotton it is usual to bring together such only as have a similar length of staple. A portion of the waste cotton of the mill is also mixed in the bing, for making the lower qualities of yarn. For higher numbers, as well as for warps, a finer quality of cotton must be selected; and thus it will be seen that the formation of a bing is an important operation, the quality of the goods produced depending upon it. In this state the cotton contains sand, dirt, and other impurities, and the fibres are matted together by the pressure they were subjected to in packing. To open the fibres and get rid of the sand, &c. the cotton is put into a machine called a _willow_. This consists of a box or case, containing a conical wooden beam, studded over with iron spikes; this beam is made to turn round five or six hundred times a minute. The cotton, as it is torn down from the bing, is put in at one end of the machine, where it is caught by the spikes, tossed about with great violence, and gradually driven forward to the other end. The sand and other impurities fall out of the machine through an open grating at the bottom; the dust and lighter matter pass off through a series of wire openings, and the cleaned cotton is sent down a shoot into the room below.