The art of dyeing was practised to a very great extent by the ancient Egyptians, Phœnicians, Greeks, and Romans; and the island of Tyre was, in very early times, celebrated for a purple dye which was, perhaps from its costliness, used for colouring the robes of kings and emperors, from which practice purple became the imperial colour. [Illustration: Garment Frame.] The art of modern dyeing very greatly consists in the proper use of what are called mordants, that is, substances which, although they do not of themselves produce colour, so act upon the dyes as to cause them to give an intenser hue to the fabric, and also serve to make the colour permanent. The modern dyers have obtained several dye drugs unknown to the ancients, such as cochineal, quercitron, Brazil and logwood, arnotts, and indigo, which was only known to the Romans as a paint; but the vast superiority of our dyes must be principally ascribed to the employment of alum and solution of tin mixed with other substances as mordants, which give depth, durability, and lustre to the colours. Another improvement in dyeing is the application of metallic compounds, such as Prussian blue, chrome yellow, and manganese brown, to textile or woven fabrics. Our readers will see from what has been said of mordants how what are called fast colours are obtained, fast colours meaning colours which will not be affected even by the liquor of the dye bath. Another very necessary subject of information in relation to dyeing is the fact that different substances, such as silk and wool, will not be equally affected by the dye in which they are placed, since the particles contained in the composition of these substances have different degrees of what is called affinity, that is, they combine in a greater or less degree with the component matter of the dye stuff. [Illustration: Vats and Copper Pan. Wringing Machine.] We have already said something of the preparation of cotton. The operations to which silk and wool are subjected before being dyed are intended to separate superfluous substances from the animal fibre, and to make that fibre more easily unite with the colouring particles. Silk is scoured by means of being boiled in water and soap, whereby the animal varnish is removed from the surface; if intended to be very white, it is bleached by humid sulphurous acid. Wool is first washed in running water to separate its coarse impurities, and is then freed from the greasy animal matter secreted from the skin of the sheep by means of ammoniacal liquor, soap and water, or a solution of soda. It is finally bleached by the fumes of burning sulphur, or by aqueous sulphuric acid. [Illustration: Dipping Copper, Winch, Punching, &c.] What are called tinctorial colours, as distinguished from mordants, are either simple or compound. The simple are black, brown or dun, blue, yellow, and red; the compounds are grey, purple, green, orange, and others.