170 Dr . Thomas Thomson on [March. 



the grass, and exposed to the sun for a few days, which 

 finishes the clearing. 



Such is a very short, but accurate, sketch of the 

 Turkey-red dyeing, as practised in the principal works in 

 Glasgow. Many attempts have been made to shorten the 

 processes, but hitherto without success. The impregnation 

 with oil, or rather soap, is essential. If one, two, or three 

 immersions be omitted, the- red is inferior in proportion to 

 the omissions. Doubtless this soap combines with and 

 remains attached to the cloth. And the same remark 

 applies to common soap. 



Cloth bleached with chloride of lime does not produce a 

 good red. Doubtless the fibres of the cotton wool combine 

 with lime or rather with sulphate of lime, which, by decom- 

 posing the oleaginous soap, prevents it from combining with 

 cloth. But cloth bleached by the old process, namely, 

 boiling in ley or soap, and exposure to the action of the 

 sun answers perfectly. The colours would be as good 

 without the galls as with them. But there would be con- 

 siderable difficulty in sufficiently impregnating the cloth 

 with the alum liquor, without its being previously passed 

 through the alum decoction, especially if the cloth be in 

 the least degree greasy. 



The whole cloth, of which a specimen is shown at No. 18, 

 is dyed Turkey-red. The white stars with eight rays con- 

 stitute an after process, and are formed by discharging the 

 dye by means of water impregnated with chlorine. Fifteen 

 pieces of cloth, dyed Turkey-red, are laid flat upon each 

 other on a plate of lead of the size of the pocket handker- 

 chief. Another plate of lead is laid over them, and the 

 two plates are pressed violently together, either by means 

 of screws, or in the more perfect establishments, by the 

 Bramah press, exerting a pressure of about 200 tons. 

 Through the upper plate are cut holes corresponding exactly 

 with the star, cross, &c, to be discharged on the cloth. A 

 solution of bleaching powder, mixed with an acid to set the 

 chlorine at liberty, is made to flow over the upper plate, 

 and forced by ingenious contrivances to pass through the 

 cavities cut in the plate. It penetrates through all the 

 fifteen pieces of cloth, discharging the colour, while the 

 violent pressure effectually prevents it from spreading to 

 those parts of the cloth which are to retain the colour. 



