136 ON BLEACHING. 



called " bucking." The subsequent process of bleaching was done by 

 exposure on the grass, which was called " crofting," and these operations 

 were repeated five or six times, extending over a period of eight or ten 

 weeks. The first advance upon this tedious process was made by Dr 

 Home, of Edinburgh, who substituted a very weak solution of sulphuric 

 acid for the butter-milk, the rye-meal, and the bran operations previously 

 employed, and by this means he accomplished the same result, and in a 

 shorter time than by the buttermilk process, which had required two 

 months. In the year 1 787, an important change took place in consequence 

 of the discovery by Mr Scheele, of Sweden, of a chemical compound, such 

 as is now designated chlorine, and this was used as a substitute for exposure 

 to the atmosphere. The repeated experiments of Berthollet added considera- 

 bly to the facts already known ; but the practical effects of these dis- 

 coveries were more fully brought out by ]\Ir Watt and Dr Henry, and it is to 

 them that the chief merit is due of introducing the new mode of bleaching 

 cotton goods. To those who are familiar with the history of the cotton 

 manufacture, it will be apparent that bleaching, as a distinct pursuit, had 

 by this time become a necessity of the trade ; therefore, the manufacturer 

 consigned to the bleacher, who was originally called a whitster, his woven 

 fabrics in th e state in which they came from the loom, loaded as they were 

 with impurities ; and the following is described as the course of operations 

 by which he undertook to whiten them. The loose fibres of cotton, adher- 

 ing to the surface of the cloth, were removed by passing the whole length of 

 the piece over a curved plate of iron heated red hot, — an operation that 

 required to be done with great velocity to prevent any injury being sus- 

 tained to the goods. The cloth was then deposited in a cistern of water, 

 or in a weak alkaline lye, where it would remain, perhaps, for some weeks 

 until the flour paste, used as dressing by the weaver, had become softened 

 by fermentation. The removal of the paste and other matter contained in 

 the web was accomplished by the agitating process of a dash wheel, or cylin- 

 drical box revolving on its axis, having four compartments, or internal 

 divisions, radiating from the centre, in which the bundles of cloth were 

 deposited. A supply of water was being injected at the sides of these 

 compartments, to cany off the impurities as they were liberated by 

 the jolting concussions created at every revolution of the wheel. 

 This invention was deemed a great advance upon the previous practice of 

 dragging the pieces by hand through a stream of water in the water-pits 

 constructed for the purpose. The cloth was next boiled in lime-water, and 

 another operation of the dash-wheel succeeded. The lime-water had to be 

 expressed from the cloth by passing the whole length of each piece 

 betwixt a pair of revolving rollers, called " squeezers." It was then 

 immersed in a composition called " chemical," and when taken out was 

 carefully washed in cold water. These operations, more or less varied in 

 their character and arrangement, were repeated a number of times ; the 

 cloth had some weeks of exposure in the grass fields, with an occasional 

 sprinkling of water to aid the process of whitening, and was then con- 



