4 /I.) And accuidingly, on the 9th of the following month, " he Frocluced another specimen ul staining with yellow. red, green, blue, and purple colones, which he said would endure washing with warm water and soap." It was not to be expected, however, that, in the very im perlect state of chemical science at that time, a few ran dom experiments could give much information to prac tical dyers, who had better oppoitunities of observing the result of fortuitous mixtures, and were well prepared to take advantage of whatever accident might to their notice. We accordingly find, that for nearly a century afterwards, no important improvement in dyeing was suggested by men of science in this coun try.
23. In France, industry, which had languished during the administration of Incline!! and \lazarin, was revived by the fostering care of Colbert, and raised to a high pitch of pre-eminence among that of the other nations of Europe. That enlightened statesman, among other objects of his care, turned his attention to the improve ment of dyeing. lie invited the most skilful artists to settle in France, and afforded every encouragement to the establishment of manufactories in various parts of the country. In order to correct, as well as to prevent the frauds which is C re practised by dyers, he published, with the assistance of M. I)'Albo, a set of regulations in 166o, and afterwards in 1672, under the title of In struction generale et pour In trinture des Mines et ma nufactures des !dines do toutes nuances, rt hour la cul ture des drogues qu'on y eniploie. This legislator first endeavours to show that dyeing is an object deserving public attention, from the additional value which it con fers upon many of the articles of commerce. " If the manufactories of silk, wool, and thread, are to be reckon ed among those which most contribute to the support of commerce, dyeing," says Colbert, " which gives them that striking vatiely of colour, by which they resemble what is most beautiful in nature, may be considered as the soul of them, without which the body could scarcely Wool and silk, the natural colour of which ra ther in' icates the rudeness of former ages, than the ge nius and improvement of the present, would be in no great request, if the art of dyeing did not furnish attrac tions is loch recommend them even to the most barba rous nations. All visible objects arc distinguished and recommended by colours ; but, for the purposes of com merce, it is not only necessary that they should be beau tiful, hut that they stun Id be good, and that their dura tion should equal that of O.( materials which they adorn." The regulaiioos of Colbert were ino•led, however. ra ther as restrictions to cont•oul, than as directions to in struct the dyers in the management of their operations.
admitted the former division of dyers "en grand," ss ho were confined to colours deemed permanent, and dyers "en pent feint," who were permitted to dye only such as were fugitive ; while they particularly specified the different substances which both were to employ in their respective processes. These restrictions, which were imposed chiefly with the view of guarding the pub lic against imposition, would have been productive of still greater evils than those they.•ere intended to ob viate, had they not been easily eluded, and had not the government at the same time held out the promise of re wards to those whose experiments contributed to the pro gress of the art.
26 During the administration of M. D'Orry, tho " Instruction" of Colbert was in a great measure annull ed by a new legislative act, passed in 1737, which re moved the restrictions that had been imposed upon the practical operations of dyeing, and afforded more scope for the improvement of the art. 1)ufay, who was con
sulted in drawing up this act, appears to have been the first who entertained just notions concerning the cause of the adhesion or colouring matters to stuffs, particu larly in those cases in which an immediate affinity sub sists between them. Without this affinity, he stated, that the cloth in a dyeing bath would never acquire an intensity of colour greater than that of the liquor in which it was immersed, but share the colouring parti cles, by a mechanical division, equally between itself and the bath ; a state of things which is by no means conformable with experience, as the stuff sometimes attracts all the colouring matter, and leaves the liquor in which it was dissolved perfectly limpid. "This seems to indicate," says 1)ufay, "that the ingredients have less attraction for the water than for the particles of the wool." lie also observed the different degrees of attraction which different substances, as wool and cotton, exert upon co louring matters; but he appears to have had no just opinion concerning the operation of mordants, or those substances which are sometimes necessary to connect the colour with the stuff. llis successor I lellot publish ed an excellent practical treatise on the methods of dye ing wool; hut all his theoretical notions were led astray by a very absurd hypothesis, which he seems to have adopted without the smallest proof. In all the processes of dyeing, he conceived that a sulphate of potash was formed ; and that this salt, being sparingly soluble in cold water, and little affected by air or light, first dilated the pores of the stuff to be dyed, thus preparing it for the reception of the colouring particles, and afterwards wedged these particles so closely together, that it be came impossible for them to make their escape. This hypothesis, which was neither supported by fact, nor countenanced by sound reasoning, was admitted without proof, and regarded for a considerable length of time as a true explanation of the cause of the adhesion of the colouring matter to the stuff. " I believe," says he, " it may be laid down as a general principle in the art of which I ant now treating, that all the invisible mecha nism of dyeing consists in dilating the pores of the body to be dyed, in depositing in them particles of foreign matters, and retaining them there by a kind of covering not liable to be affected by water, rain, or the rays of the sun; in choosing colouring particles of such a degree of fineness as to be tendered sufficiently fixed in the pores of the stuff opened by the heat of boiling water, and again constricted by cold, and also coated by the kind of varnish which the salts employed in its preparation had left in those pores; whence it follows, that the pores of the fibres of the wool which has been wrought, or is to be wrought into cloth, should he cleansed, enlarged, coated over, and then constricted, so that the colouring particles may be retained in them nearly in the same manner as the diamond is retained in the collet of a ring." Notwithstanding the erroneous views of Hellot, the inferences which he deduced from them were not destitute of practical utility, and many of the processes which he recommended may be followed with the same advantage as if they had been derived from more scienti fic principles. Nor shall we wonder at this, if we reflect that the most correct theory seldom does more than illus trate the nature of the practical operation which expe rience has previously discovered to be useful.