DYER, a person who professes the art of dyeing, all manner of colours. See Dyeing.

DYER (Sir James), an eminent English lawyer, chief judge of the court of common pleas in the reign of Queen Elizabeth. He died in 1581; and about 20 years after was published his large collection of Reports, which have been highly esteemed for their succinctness and solidity. He also left other writings behind him relative to his profession.

DYER (John), the son of Robert Dyer, Esq.; a Welsh solicitor of great capacity, was born in 1700. He passed through Westminster-school under the care of Dr Freind, and was then called home to be instructed in his father's profession. His genius, however, led him a different way; for besides his early taste for poetry, having a partial no less strong for the arts of design, he determined to make painting his profession. With this view, having studied a while under his master, he became, as he tells his friend, an itinerant painter, and wandered about South Wales and the parts adjacent; and about 1727 printed Grongar Hill. Being probably unsatisfied with his own proficiency, he made the tour of Italy; where, besides the usual study of the remains of antiquity, and the works of the great masters, he frequently spent whole days in the country about Rome and Florence, sketching those picturesque prospects with facility and spirit. Images from hence naturally transferred themselves into his poetical compositions: the principal beauties of The Ruins of Rome are perhaps of this kind; and the various landscapes in The Fleece have been particularly admired. On his return to England, he published The Ruins of Rome, 1740; but soon found that he could not relish a town-life, nor submit to the assiduity required in his profession. As his turn of mind was rather serious, and his conduct and behaviour always irreproachable, he was advised by his friends to enter into holy orders; and it is presumed, though his education had not been regular, that he found no difficulty in obtaining them. He was ordained by the bishop of Lincoln, and had a law degree conferred on him.

About the same time he married a lady of Colehill named Enfor; "whose grandmother (says he) was a Shakespeare, deposed from a brother of every body's Shakespeare." His ecclesiastical provision was a long time but slender. His first patron, Mr Harper, gave him, in 1741, Calthorpe in Leicestershire, of 80l. a-year, on which he lived ten years; and in April 1757 exchanged it for Belchford in Lincolnshire, of 75l. which was given him by lord chancellor Hardwicke, on the recommendation of a friend to virtue and the muses. His condition now began to mend. In 1752, Sir John Heathcote gave him Coningsby, of 140l. a-year; and in 1756, when he was L.L.B. without any solicitation of his own, obtained for him from the chancellor Kirby Dye

Mr Dyer's character as a writer has been fixed by three poems, Grongar Hill, The Ruins of Rome, and The Fleece; wherein a poetical imagination perfectly original, a natural simplicity connected with and often productive of the true sublime, and the warmest sentiments of benevolence and virtue, have been universally observed and admired. These pieces were put out separately in his lifetime; but after his death, they were collected and published in one volume 8vo, 1761; with a short account of himself prefixed.

Dyer's Weed, in botany. See Reseda.

Dyeing

In the utmost latitude of the word, may be defined, The art of tingeing cloth, stuff, or other matter, with a permanent colour, which penetrates the substance thereof.—It is, however, commonly restrained to the art of tingeing silk, wool, cotton, and linen, with different colours; and, as such, is practised as a trade by those who do not meddle with any of the other branches, as staining of leather, &c.

The dyeing art is of great antiquity; as appears from the traces of it in the oldest sacred as well as profane writers. The honour of the invention is attributed to the Tyrians; though what lessens the merit of it is, that it is said to have owed its rise to chance. The juices of certain fruits, leaves, &c. accidentally crushed, are supposed to have furnished the first hint: Pliny affirms us, that even in his time the Gauls made use of no other dyes. It is added, that coloured earths and minerals, washed and soaked with rain, gave the next dyeing materials.—But purple, an animal juice found in a shell-fish called murex*, conchylium, and purpura, seems from history to have been prior to any of them. This indeed was reserved for the use of kings and princes; private persons were forbidden by law to wear the least scrap of it. The discovery of its tingeing quality is said to have been taken from a dog, which having caught one of the purple fishes among the rocks, and eaten it up, stained his mouth and beard with the precious liquor; which struck the fancy of a Tyrian nymph so strongly, that she refused her lover Hercules any favours till he had brought her a mant' e of the same colour.

Pliny seems to ascribe the invention of the art of dyeing wool to the Lydians of Sardis: Inciferi lanas Sardibus Lydi; where the word inciferi must be understood. But a modern critic suspects a false reading here; and, not without reason, for Lydi substitutes Lydda, the name of a city on the coast of Phoenicia, where the chief mart of the purple dye was.

After the Phoenicians, the Sardinians seem to have arrived at the greatest perfection in the dyeing art; inasmuch that Παραμελίνη, Sardinian dye, passed into a proverb among the Greeks. Till the time of Alexander, we find no other sort of dye in use among the Greeks but purple and scarlet.—It was under the successors of that monarch that these people applied themselves to the other colours; and invented, or at least perfected, blue, yellow, green, &c.—For the ancient purple, it has been long lost; but the perfection

Vol. VI. Part I.

to which the moderns have carried the other colours, abundantly indemnifies them of the loss. It is still, however, greatly to be doubted whether the permanency of the modern colours at all equals that of the ancient ones; though it is certain that the former greatly exceed them in brightness.

Sect. I. Theory of Dyeing.

Before we can enter into any consideration of the salts the true theory of dyeing, it is necessary to make the following observation concerning the practice, namely, of fixing. That salts are almost the only means we are acquainted with by which any colouring substance can be made to fix itself upon those matters which are the common subjects of dyeing. A solution of cochineal, for instance, will of itself impart no permanent colour to a piece of woollen cloth put into it. The red colour of the cochineal will indeed stain the cloth while it remains immersed in the solution; but as soon as it is taken out and washed, this temporary stain will immediately vanish, and the cloth become as white as before. If now the cloth is dipped in the solution of any saline substance, alkalies alone excepted, and then immersed in the solution of cochineal for some time, it will come out permanently coloured; nor will the colour be discharged even by washing with soap and water. If a quantity of salt is added to the solution of cochineal, and the cloth put in without being impregnated with any saline substance, the effect will be the same; the cloth will come out coloured; only in this last case, it must be well dried before washing it with soap; or most of the colour will be discharged.

By comparing this with what is delivered under the article Colour-Making, n° 13, 14, we shall be able to form a pretty rational theory of dyeing. It is there remarked, that a saline substance (solution of tin in aqua regia) had a surprising power of coagulating the colouring matter of certain solutions, such as cochineal, Brazil-wood, logwood, &c. If therefore a piece of cloth is previously impregnated with this solution, and put into the colouring one, it is plain that some part of the colouring matter will be coagulated by the solution remaining in the cloth, in the very same manner that it would have been if a small quantity of the saline solution had been poured into the other. The cloth therefore will take up a part of the colouring matter, which cannot be discharged but by entirely discharging the solution of tin. This, however, seems to unite itself with the cloth very firmly, so that scarce a particle of colour will be discharged by washing in plain water, or even with soap; nor can the whole be taken out without boiling the cloth in a solution of fixed alkali.

Though solution of tin produces this coagulation in the most remarkable manner, it is not to be doubted that the same power is possessed in some degree by most of the neutrals and imperfect salts. Alum possesses it very considerably, though not so much as solution of tin; and hence that salt is very much used in dyeing, as well as sugar of lead, which also has a very strong power of coagulation. The process of dyeing, therefore, seems to be most analogous to that of the coagulation or curdling of milk. Before it has suffered this change, the milk is easily miscible with water; but after it is once coagulated, the curd, or caseous part, is very difficultly soluble in any liquid whatever. In like manner, the colouring matter in the solution of cochineal, before the cloth is put in, is easily soluble in water, and may be diffused through any quantity of fluid: but no sooner is the cloth dipped in it, than the saline substance contained in the cloth coagulates that part of the colouring matter which lies in immediate contact with it; and as all the fluid successively comes into contact with it, the whole of the colour is by degrees coagulated and deposited on the cloth.

To account for the strong adhesion of the colour to the dyed cloth, several hypotheses have been formed. One is, That the fibres of wool, silk, &c., are hollow tubes; that the colouring matter enters them; and, after being there coagulated, flows itself through the fine transparent sides of the tubes.—Another considers these filaments as solid lengthwise, but having all round their sides an infinite number of small pores like the extremities of the fine absorbing and exhaling vessels of the human body. In these pores, according to the hypothesis, the colour is lodged; and as the pores are placed exceedingly close to one another, the fine threads appear to our eyes of one uniform colour.—A third is, That the fibres are solid, or at least with respect to us may be considered as such. The saline substance, whatever it is, that is employed to make the colour strike, sinks into the surface, partly corrodes and unites itself with it into a third kind of substance no longer soluble in plain water, nor even easily by soap, but which still preserves its coagulating quality. According to this hypothesis, the dye lies entirely on the outside of the fluff, and continues as long as the effect of the salt continues upon the fibres of the matter to be dyed.

Concerning the truth of these hypotheses, or indeed any others that can be invented, it is impossible to bring any decisive proof. It seems, however, more probable, that the process of dyeing is accomplished by a coagulation of the colouring matter itself, rather than by any agglutination of it to the fibres by means of a vitriolated tartar, as Mr Hellot supposes. According to this gentleman's theory, a vitriolated tartar is generated in every process for dyeing, and proceeds from the acid of the alum and alkaline basis of the tartar used in the preparations, or in some of the dyeing ingredients themselves. He supposes that the pores of the fluff are cleansed and enlarged by the preparatory salts, and by the boiling water, in such a manner as to receive the colouring particles, which particles are afterwards detained by the contraction of the pores occasioned by cold; and further, that these pores are lined with a saline crust of tartar or vitriolated tartar.

On this theory the translator of the Chemical Dictionary has the following observations. "Mr Hellot has not shown that pure fixed alkali is incapable of producing the effects which he attributes to his tartar and vitriolated tartar; and both these salts, though they are difficult of solution, and require a great quantity of water for this purpose, will yet dissolve at last; and therefore, if the colouring particles were fixed chiefly by means of these salts, they might be washed out by a large quantity of water; which we find to be contrary to experience.

"We shall find it more difficult to substitute a true theory than to refute that of Mr Hellot. Many experiments ought to be previously made. Nevertheless, it may be observed, That the colorific particles of most substances used in dyeing seem to be insoluble in water, in spirit of wine, and even in alkaline lixiviants; that their diffusion through these liquids is caused merely by their adhesion to certain gummosus and resinous particles; and that they may be disengaged from those gummosus and resinous matters, by applying a piece of fluff to which they have a greater adhesive power, which seems to be the case of the root-coloured and blue dyes; or by applying another substance to which these particles have a greater power of adhesion; such as the earth of alum, in those dyes where that salt is used, together with some other substance, as fixed or volatile alkali, capable of decomposing alum; or as the ferruginous earth of the green vitriol in black dyes, to which the colorific particles of the galls adhere; which earths are capable of applying themselves and of adhering to the fluffs. The separation of the colouring particles from the gummosus and resinous matters is probably facilitated by the addition of acids and neutral salts, which may coagulate in some measure the vegetable matters, and leave the colorific particles disengaged; so that they may apply themselves to the fluff, or to the earths above mentioned."

In a treatise on this subject by M. de Apligny, the nature of the different substances usually subjected to ligny's treatment is particularly considered. These are wool, silk, cotton, and linen. Wool was probably the first substance to which any kind of dye was applied, and which might probably have been done even in the fleece, while mankind, in their rude state, wore the skins of animals. When some further progress in arts was made, and the method of manufacturing wool into worsted and cloth discovered, the dye would then be applied to it; but it was not till a considerable time afterwards that silk and cotton were known; and the art of dyeing linen is mentioned as a new invention even in the time of Pliny.

Wool, according to our author, consists of tubes, which, like hair, contain a medullary substance, but throughout their length are sieves with an infinite number of lateral pores; and in proportion to the greater or lesser number of these pores, the woolly fibres are more or less curled. The reason assigned for this is, that "the more interruptions there are in the continuity of any body, the more flexible it will be; the fibres of the wool therefore being curled must have many..." many pores, and consequently great room for the extraneous substance which may be not only lodged in the exterior pores, but even penetrate into the whole extent of the tubes, after the medullary substance has been expelled. It is not therefore to be wondered at, if wool, being of all substances that are made into stuffs the most porous, should be the most easy to dye, and imbibe the greatest quantity of colour."

Silk, according to our author, may naturally be supposed to proceed originally from the mucilage of the mulberry leaf on which the animal feeds, and which he imagines is converted into an animal substance by a combination with volatile alkali; but which, by the evaporation of a thin oil, and part of this alkaline matter, becomes tough and hard. An example of something similar to this is observed on the leaves of the ros folia, on which there are found some drops, which being touched while the sun shines upon it may be drawn out into fine and very white threads. The consolidation of the silk is also promoted by a yellow substance with which the animal impregnates the thread; and this seems to be a concrete oil something similar to wax. Silk thread therefore is nothing else than a continued series of molecules of this indurated gluten; but as in this dehiscence the molecule will remain at unequal distances, there will necessarily be inequalities, and consequently pores in the thread; but as these pores are only on the surface of the thread without any interior concavity as in the wool, it follows, that silk can admit no particles into its pores, but such as are extremely subtile and in very small quantities; that even the particles admitted require a stronger mastic or fixing substance than wool, since they are only superficial, and incapable of penetrating. Hence silk is much more difficult to dye permanently than wool, and requires likewise a much greater quantity of colouring materials; two ounces and a half of cochineal being required to give the same shade to a pound of silk that one ounce will give to a pound of wool. For the same reason also the colours on silk are less permanent than on wool.

Cotton being a true vegetable substance must necessarily have its fibres hollow like wool, that the juices may circulate properly; but as these are a great deal finer, the cotton is therefore much more difficult to dye. The exterior and lateral pores of cotton are likewise filled with a kind of oil, which it is necessary to expel before the dye can be given.

Flax may likewise be supposed porous, but that its pores are much smaller than those of any of the substances already mentioned. The detached and separated fibres resemble silk in some degree, only that, being more dry and compact, they take the dye with still more difficulty than even cotton; and from the different textures of these substances we may reasonably ascribe the different shades which are taken by them even when the same dyeing ingredients are made use of. This holds good also with respect to stuffs differently manufactured, though of the same kind; the pores being necessarily contracted by certain kinds of fabrication, whence they receive a smaller quantity of the dye; and hence scarlet cloth, when cut, appears white internally, the colouring atoms being too large to penetrate it, which, however, does not happen in the stuffs which have been previously dipped in solution of alum.—A difference of shade will also be occasioned by the different positions and delicacy of the fibres of the stuff; and by this also a difference is made in the brightness of the colour.

With regard to the operation of those substances commonly made use of for fixing the dye, our author remarks, that lime seems defined by the Author of nature for binding and uniting the two seemingly opposite substances of salts and earth. "Fire (says he) makes it soluble in water, and therefore easily used; but it again becomes indissoluble by the contact and influence of the air; and these properties render it capable of forming, when united to other bodies, an unalterable cement." We know several mixtures of this kind, of which lime is the basis, and that in consequence of these properties it confirms the solidity of many colours.

Alum has the property of attracting the colouring particles of the dye as well as of fixing them; and Pliny informs us that this property was known to the ancients. They made use of certain earths of the argillaceous kind, which they called creta argentaria, salamandra, and amarilla, to imbibe the colour from infusions of dyeing ingredients; and they became much sooner saturated with the colour than wool itself. There are two kinds of alum made use of in dyeing, viz. roch alum and Roman alum. The first is always used for blues and the colours including to black; but as this generally contains some particles of iron, the Roman alum is preferred for the more lively colours, as it contains nothing capable of tarnishing their beauty. The colours are brightened by the whiteness of the earth, while its tenacity, produced by some kind of viscosity with which it is combined, makes it more solid; and the plastic quality of the earth makes it take the form of the pores in the substance to be dyed; whence a greater permanency of colour must necessarily ensue.

There are several other saline substances made use of in dyeing, particularly nitre, sea-salt, sal ammoniac, and tartar, &c. By the three first the red colours are always rendered more dark-coloured, while the others enliven the colour and give it an orange hue. Neutral salts with a metallic basis serve to strengthen the colour, which varies its shade according to the nature of the metallic substance with which it is combined. Green and blue vitriol are the most commonly used in this art.

In explaining the theory of the art of dyeing, our author considers the whole as an effect of attraction; and in order to set forth this matter in a proper light, it is necessary, in the first place, to explain the conditions requisite for the action of bodies upon one another in this way. These conditions are, 1. That the attractive power be mutual in both. 2. That they should be placed at a distance from each other proportioned to the force of attraction. 3. That this force be superior to that by which the colouring matter is attracted by the water. Hence it is necessary for dyeing stuffs of any kind, that the dye should consist of small particles suspended in a liquid, in such a manner that they may be separated by a substance which has a greater affinity with these minute bodies than water. Some of these substances, however, are not attracted by the earth of alum, and these enter the pores of the cloth without its assistance; but in such as require the affixture of alum, the particles are fixed by the power of attraction, at the same time that the acid of the alum is softened by its combination with the principles of these particles; this acid having served merely as a vehicle for distributing equally into all the pores of the stuff that earth which it held in a state of the greatest possible divisibility.

Our author next proceeds to contest the theory, that salts, even such as are the most insoluble, can maintain their stability in the pores of the stuff, however insoluble the salt may be in water. He observes that this insolubility, however great, could not prevent a great quantity of it from being carried off by water, and consequently the colour from being injured by the decomposition of these salts; but fixed earth, such as that of lime and alum, which from its nature obstinately retains the phlogistic principles of all colours, must necessarily produce such as cannot be destroyed but by the strongest acids.

Colours, in the opinion of our author, depend entirely upon phlogiston. It is well known that, by the simple addition of any salt to an oily, vegetable, and colouring substance, we may either change or totally expel its colour; because any salt, either simple or compound, destroying the combination then subsisting, a new reflection of the rays of light must necessarily take place. In such substances therefore as cannot have their colour affected by any salt, the phlogiston is most probably in the most perfect combination with the other principles. Were we thoroughly acquainted with this combination, we should be able to make perfect compositions for dyeing, similar to what artificial cinnabar is for painting; but though we certainly know the effects produced upon some kinds of oils by salts, and can decompose some colouring substances and separate their principles; we are still unacquainted with the manner in which these principles are combined; and therefore every effort of this kind has hitherto been found insufficient for the purpose.

As the colour (says our author) depends upon the shape or figure of the constituent particles of the colouring bodies, the shade may be varied by changing their figure, but the permanency of the colour is at the same time diminished; because it is impossible to produce this change without altering the principles to which they owe their permanency; and this is the case with cochineal. The shades of its colour are easily varied by acids and alkalies.

M. de Apligny then proceeds to account for the action of acids and alkalies upon colouring substances. Cochineal is rendered darker by alkalies, and always becomes of a deep purple on adding them; and the volatile alkali is found to be more efficacious in this respect than the fixed kind. These salts he supposes to produce this effect, because they are natural solvents of animal substances; which, however, they are incapable of dissolving without combination, causing only a composition without the dilution of any principle. This combination gives a degree of density to the colouring particles which they had not before; and thus inclines them to black, by occasioning a greater degree of refraction in the pencils of rays. Acids, on the other hand, especially those of the mineral kind, burn the oil, and absorb the phlogiston, which is the principle of all colours. By the violence of their action a part of the phlogiston and volatile alkali evaporates, the colouring matter becomes more rarefied, and reflects a greater number of the rays of light; whence it necessarily acquires a colour nearly yellow, and even quite so if a proper quantity be added; this being, according to our author, of all colours the nearest to white or transparency. Hence it is not customary for dyers to make any use of fixed alkali when cochineal is the colouring substance, as it would make too great an alteration in the consistence, and, by mixing with the animal oil, form a soap which would render the colour insoluble in water, and consequently of the false kind of dye; the oil already mixed with fixed alkali being no longer at liberty to combine with the earth of alum. But after the substance has been already dyed, the fixed alkali may then be used with advantage in some cases; because the colouring substance being already converted into what our author calls a mastic, cannot be dissolved by the menstruum unless the latter be used in very great quantity.

Acids, according to M. de Apligny, are more destructive in their action than alkalies; and the oil of vitriol, formerly used, always containing some ferruginous particles, a kind of Prussian blue was formed, which rendered the colour purple rather than otherwise; and even by simple boiling in an iron vessel, the solution of cochineal always assumes a purple colour. The activity of spirit of nitre, which has been substituted in place of oil of vitriol, is so great, that it has been found necessary to give it a basis on which it might in part exhaust itself, and, by communicating part of its phlogiston, render it less greedy of the cochineal. This basis is tin, which formerly was dissolved by spirit of nitre, but now by aqua regia, which was found to dissolve it more completely. Our author's method of using this solution, however, is not by diluting it in water, and then by dipping the stuffs in it previous to their being dyed. "This preparation (says he) would not be sufficient; for by diluting with a great quantity of water, a part of the calx would precipitate and be reduced into particles larger than when dissolved in acids, especially if used alone and separate from the dye; the acid in that case not acting on the colour with sufficient force to enliven it. Only part of this solution, therefore, is added to the cochineal liquor; and the acid then abandoning the tin, and combining with the oil of the cochineal, the calx of the metal seizes the colouring matter as it precipitates, and, as Mr Hellot observes, forms a kind of lacquer which infiltrates into the pores of the stuff, and is there retained by a gluten given by the starch which was added to the dyeing liquor. Hence it is easy to conceive why the scarlet dye is much less solid than the crimson; the lacquer being much drier than the simple colouring particles of the cochineal, is in this state nearer to the nature of the mineral colours. The oil and the animal gluten, which in the crimson dye form with the earth of alum a mastic, are destroyed by the acid, and the starch then added is an insufficient substitute."

The same thing that has here been mentioned of cochineal applies equally to gum-lac and kermes; both of which afford a scarlet dye. The kermes, he thinks, has the advantage of being composed of finer particles, which more easily penetrate the pores of silk or cotton. Silk indeed, on account of the smallness of its pores, takes up only a part of the cochineal; but it extracts the whole of the colour from the cochineal, and the colour is also more fixed, probably because the shrub on which the insect is nourished communicates its astrigency, or contains a greater quantity of oil. Cotton may likewise be dyed with kernels, though cochineal cannot penetrate its pores.

But in whatever way the salts used in dyeing do act, it is certain they are capable, except in a very few instances, of fixing and giving a lustre and permanency to the colour which otherwise could never be obtained. The exception to this general rule most commonly known is that of indigo. This is a fine blue fecula produced by fermentation from the leaves of the Indian plant called anil. It is very difficult of solution; however, it may be dissolved by alkaline salts, concentrated oil of vitriol, orpiment, or combinations of sulphur with quicklime. If a quantity of indigo is dissolved in a fixed alkali (for volatile alkalies will not dissolve it), the solution is always green, which is the natural colour produced in all vegetable blues by the alkali: but if any piece of stuff is put into this solution, though it remains green while immersed in the liquid, the moment it comes in contact with the air, the dissolving power of the alkali is totally destroyed; the indigo is precipitated upon the cloth, resumes its native colour, and dyes the cloth blue.

The cause of this precipitation is very difficult to be investigated. Perhaps it may be owing to an attraction of fixed air by the alkali from the atmosphere, which renders the salt unable to dissolve the indigo any longer. The adhesion of the colour seems merely owing to an attraction between it and the cloth; for the alkaline salt can contribute nothing to this, but would rather have the contrary effect. Perhaps, however, the great solvent power possessed by alkaline salts, by perfectly clearing away every kind of foreign matter, may bring the indigo and cloth into nearer contact with each other, than when it is dissolved in any other way; and consequently the attraction will in these cases be the stronger. This seems to have some probability; for when indigo is dissolved in vitriolic acid, as in dyeing Saxon blue, the colour is much more easily discharged.

Another exception is in the juices of some vegetables, such as the nuts of the anarcadium. This produces, without addition, a most deep and lasting black, never to be washed out or discharged by any means whatever. Several other plants are to be found in different parts of the world, which give an indelible black stain upon linen without addition; and the colouring matter of these seems to adhere by means of a very tenacious gluten, with which it is mixed, and which, when once thoroughly dried, can never be again dissolved. In this respect, these black staining colours seem analogous to the purpura of the ancients; which stained indelibly without addition, and was of an exceedingly viscous and adhesive nature.

**Sect. II. Practice of Dyeing.**

The materials for dyeing different colours are so many and various, that an enumeration of them all is scarce to be expected. The same difference, however, takes place among the materials for dyeing which we have observed to take place among those for Colour-

Making. Some ingredients produce durable colours, which cannot be discharged either by exposure to the air or by washing with soap: others, though they may be made to stand the action of soap pretty well, cannot by any means be enabled to resist the action of the air. These are distinguished by the different names of true and false, permanent and fading, &c.; nor is there any method yet discovered of giving the false colours an equal degree of durability with the true ones. This hath been attempted by mixing a permanent and a fading colour together; in which case it was thought that the former would impart somewhat of its durability to the latter: but this hath always been found to misguide; the fading colour soon flying off, and leaving the permanent one behind. Nay, in many cases this does not even happen; for, by some means hitherto not accounted for, the volatile colour imparts its volatility to that which would otherwise be permanent. The same hath also been attempted by dyeing a piece of stuff partially with a fading colour, and then completing the dye with a permanent one. In this case it was hoped that the fading colour being covered over, and defended from the injuries of the air by the permanent one, would necessarily become equally durable, or at least remain a much longer time than if the stuff was dyed with it alone. But this also hath been found ineffectual; and the fading colour hath been dissipated as soon when covered with a permanent one, as when left without any such cover.—Solution of tin in aqua regia will give most of these fading colours an high degree of beauty, and some share of durability, though even that is not able to make them equal to the others.—The most permanent dyes we have are cochineal and gum lac for fine reds and scarlets; indigo and woad for blue; and, when mixed in different proportions with cochineal or lac, for purple and violet colours. Weld, and some other vegetables, for yellow; and madder for coarse reds, purples, and blacks.—The fading colours are much more numerous. In this class are included Brazil-wood, logwood, peach-wood, red-wood, fustic, turmeric root, annatto, archil, &c. &c.

With regard to the salts made use of in dyeing, it Salts to be hath been but too often customary to jumble together used in dyeing such a quantity of different ones, that it was not only impossible to know in what particular salt the virtue resided, but often the efficacy of the whole hath been totally destroyed, and the colour entirely spoiled by such injudicious management. It is proper, therefore, where a mixture of two or more salts is intended to be made for dyeing, first to try the change of colour produced by each of the salts upon the colouring substance. If the colours are nearly alike, the mixture may be safely made as to that particular. But if the two colours produced by the different salts are very different from one another, to mix them together must be very injudicious. Thus, suppose you want to dye scarlet, solution of tin in aqua regia produces the necessary change of colour on the decoction of cochineal, and converts it into a high flame-colour, which shows it to be a proper ingredient; but to the solution of tin, it would surely be the greatest absurdity to add a quantity of saccharum saturni, the effect of which is to change the colour of cochineal to a dull purple. But though the salts taken separately should produce a colour nearly similar, another thing must be regarded, namely, whe-