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to the accused (Liv. i. 26). This office was exercised by Tarquinius Superbus alone, for tyrannical purposes (Liv. i. 49), and afterwards by the consuls (Liv. ii. 5), who were indeed a duumvirate. The Quacsitores parricidii were afterwards substituted for the consuls, and these were mentioned in the laws of the Twelve Tables (Pompon. l. ii. S. 23 D); but it seems that the duumviri were again entrusted with the administration of criminal law at the trial of Manlius Capitolinus (Gellius, xvii. 21); and they are mentioned as still existing even by Cicero (Pro C. Rabirio, c. iv. S. 12). The duumviri sacrorum, who took care of and interpreted the Sibylline Books, were also a very antient magistracy (Liv. iv. 21). Niebuhr thinks (Hist. of Rome, i., p. 298, Engl. Tr.) that the number was dictated by a wish to deal evenly with the first two tribes, the Ramnes and the Tities. The chief magistrates in the municipia were also called duumviri (Lips. Elect., i. 23), or sometimes consuls. (Cicero, in Pisonem, c. xi.) Their lictors generally carried little staves (bacilla) before them; but they occasionally arrogated to themselves the fasces. (Cicero, Agrar. ii. 34.) The duumviri navales were two officers, first elected in the year 436 A.U.C. (Liv. Epit. lib. xii.; Niebuhr's, mische Geschichte, th: iii. p. 282). Their duty was to collect, equip, man, and command the fleets of the republic (Liv. ix. 30; xl. 18 and 26). There were also other duumviri created for special occasions. DWARF is a technical term employed by gardeners to distinguish fruit-trees whose branches proceed from close to the ground from riders or standards whose original stocks are several feet in height. DWARFING TREES. Nature, in many respects, can be made to deviate from her ordinary course of procedure, in order to be subservient to the purposes of men. In nothing is this fact more apparent than in the various modes of dwarfing trees. The trees of our orchards and forests, for example, which grow naturally to a considerable size, can be made to assume all the appearances of maturity and age while only a few feet high; a forest in miniature can thus be created, which has a very grotesque and curious appearance. There are various methods of producing this effect; such as selecting peculiar kinds of stocks and grafting o them. For example, if the pear-tree be grafted upon the quince stock, or the peach upon the plum, their growth is very much retarded, and their ultimate size is comparatively small: the same effect is produced upon all other trees where there is a difference between the tissue of the stock and that of the scion which has been grafted upon it; or if dwarf varieties be grafted upon stocks of a similar constitution, though taller in growth, the former will still retain their original character. Again, if the branches be bent, and the flow of the sap in any way impeded, or if a quantity of the fibrous roots be cut away, and nourishment more sparingly supplied to the branches, we arrive at the same results. Sometimes trees are dwarfed by very severe pruning, . if this operation be performed in summer, j. although they evidently try for a length of time to overcome this obstruction to their natural size, yet they eventually assume a dwarfed and stunted habit, which, with a little care, may be retained for many years. The Chinese in particular have carried this practice to a great extent, and they ornament their fanciful gardens with miniature forests of elms, junipers, and other timber trees. The methods of dwarfing employed by the Chinese are the following:—young trees of various sorts are planted in flat porcelain vessels, and receive only so much water as is sufficient to keep them alive; in a very short time the pots are completely filled with roots, which, being hemmed in on all sides, cannot obtain a sufficient quantity of nutriment, and, as a matter of course, the growth of the stem and branches is thus impeded. The Chinese also pinch off the ends from the young shoots, mutilate the roots, lacerate the bark, tie down the branches, and break many of them half through ; in short, by every means in their power they contrive to check growth, so that, stunted and deformed by these means, the trees soon assume all the marks of age when only two or three feet high. There is another method of producing dwarf trees, which may be termed accidental: namely, selecting dwarf individuals and obtaining seed from them. It is well known that when the young seed is fertilized by the influence of the pollen belonging to its own flower, or to the same plant upon which it grows, the future progeny so produced par

f takes generally in a large degree of the nature of the parent from which it originates. Now, if seed be so tained from a variety rather more dwarf than usual, some of the plants produced by that seed will be something dwarfer than their parents. The dwarfest individuals again selected for seed will originate a race yet dwarfer than themselves; and thus, with patience and by successive generations, a variety only a few inches high may be obtained from a species two or three feet high, or even higher. This is the origin of dwarf roses, sweet williams, dahlias, and other common cultivated flowers. With the exception of this last-mentioned method, all the others, however different they may seem, proceed from the same principle; for whether we graft upon stocks whose tissue differs in organization from the scion, or whether we bend the branches, or cut or confine the roots, we prevent the full flow of the sap in all such cases, and thus advance the age of puberty and bring on a fruit-bearing state. When plants have arrived at this stage of existence, all their energies are directed to the formation of fruit; hence forcing a tree into an early state of fruit-bearing is almost synonymous with dwarfing it. DWIGHT, TIMOTHY, an eminent American Presbyterian divine, was born at Northampton, in Massachusetts, May 14, 1752. From infancy he made rapid progress in general and scholastic learning; insomuch that, at the age of seventeen, very soon after taking the degree of B.A. at Yale College, Newhaven, he was appointed master of a grammar-school in that town, and, before he was twenty, one of the tutors of Yale College. He was licensed to F. in 1777, in which year, the sessions of the college having been stopped by the war of the Revolution, he offered his services as a chaplain in the American army. The death of his father in the following year rendered it desirable that he should return to Northampton, and the rest of his life was principally occupied in discharging the duties of tuition, first as master of a private seminary, next as president of Yale College, to which office he was appointed in 1795. He also held the professorship of theology. He died January 11, 1817. His early life was extremely laborious: it is stated that while he kept school at Newhaven his time was regularly divided:—six hours of each day in school, eight hours in close and severe study, and the remaining ten hours in exercise and sleep. (Life, p. 20.) Over-exertion nearly brought on blindness: from the age of twenty-three he was continually subject to acute pain behind the eyes, and was unable, for the space of forty years, to read longer than fifteen minutes in the day. his makes the extent and variety of his knowledge, which was acquired almost entirely through the ear, the more remarkable; and the mastery which he acquired over his mental powers by discipline was so complete, that he could dictate two or three letters to different amanuenses at once, and he seldom forgot or found difficulty in producing any fact which was once stored in his memory. In 1774 he resorted to a severe system of abstinence in food and exercise, which had nearly proved fatal. He recovered a vigorous state of health, chiefly by returning to a daily course of strong exercise, and the benefit thus derived led him in after-life to devote his recreations regularly to a series of excursions, of which we have the fruits in his “Travels in New England and New York,’ 4 vols., 8vo., 1823. These contain a great quantity of information, statistical, topographical, and historical, which, considering Dr. Dwight's mental habits and opportunities, there is every reason to presume accurate: the statistics of course have long ceased to represent the present condition of the country. The historical parts, especially those relating to the Indian history, manners, and warfare, are of much interest. Dr. Dwight's chief work however is “Theology explained and defended in a series of Sermons,” 5 vols., 8vo. It is a course of 173 lectures, delivered by him as professor of divinity on the Sundays in term-time, so as to occupy about four years. His method of preaching was from very concise notes or heads, his eyes not per mitting him to undergo the labour of writing; so that this voluminous body of divinity was not committed to paper till 1805, in which year he was provided with an amanuensis at the expense of i. college. Two more volumes of his sermons, fifty-nine in number, were published in 1827, and the editor intimates that he has more behind. These contain several addressed by him annually, according to college custom, as president, to the candidates for the * of B.A., which will be read with irterest. Dr. Dwight is said to have been eminently a useful and effective as well as a learned preacher, and his life bore witness to the efficacy of his own belief. (Life, prefired to his Theology Explained.") DWINA, the largest river that falls into the White Sea, and the seventh with regard to length in the Russian dominions, originates in the confluence of two smaller rivers, the Sukhoria and Yug, near Veliki-Usstiug, in 60° 46' N.

lat., and 46° 30' E. long. The Sukhoria, a considerable.

stream, which flows out of Lake Goubinskii or Kuban, and runs in a very tortuous direction through the south-western parts of the government of Vologda, describes a course, along the whole of which it is navigable, of about 285 miles between that lake and the junction with the Yug. The Yug, flowing down from a morass on the northern range of the Volga mountains, at the southernmost point of the same government, and in the early part of its course washing the walls of Nikolsk in its progress northwards to its confluence with the Sukhoria, has a length of about 248 miles. These two rivers unite below Veliki-Usstiug and the river is thenceforward denominated the Dwina. The Dwina pursues in general a north-westerly direction through the western districts of the government of Vologda, becomes navigable before it quits them, traverses the south-western part of the government of Archangel, and discharges its waters through five arms below the town of Archangel into the bay of Dwinskaya, in the White Sea. Its length in a straight line from its source to its mouth is about 312 miles, but, including its windings, it is estimated at about 736 miles. It is navigable from the close of April to the first week in November for a distance of about 240 miles. It generally flows between high banks, and is on an average from 500 to 600 feet in width; at Archangel this width is increased to four miles. Soon after it has received the Pinega on its right bank, it forms a number of islands, which extend to its mouth. Its chief tributaries are, on its right bank, the Vouitsheyda or Vitshayda, the source of which is on the declivity of the Vertshoturi range of the Ural mountains, not far from the sources of the Petshora: this river has numerous bends, and falls into the Dwina near Kershensko, in the centre of the government of Vologda, from which point the Dwina becomes navigable; and the Pinega, in the south-western part of the government of Archangel, which becomes navigable for a distance of about 70 miles from Pineg downwards, and after a course of about 190 miles, discharges its waters into the Dwina a little above the town of Kholmogory. On its left bank the Dwina receives the Vaga, which is navigable for about 75 miles, and joins the Dwina above Poinskoi, in the government of Archangel, and the Yamza, a river navigable for about 90 miles, which has its confluence with the Dwina about 36 miles above Wilsk in the same government. The tides of the Dwina are perceptible nearly 30 miles above Archangel. The basin of the river occupies an area of about 123,900 square miles; the bed is generally of clay, covered with a thin layer of sand. It abounds in fish. DYEING is the art of staining textile substances with permanent colours. To cover their surfaces with colouring matters removable by abrasion would be to apply a pigment rather than to communicate a dye. Dye-stuffs can penetrate the minute pores of vegetable and animal fibres only when presented to them in a state of solution, and they can constitute fast, colours only by passing, afterwards into the state of insoluble compounds. Dyeing thus appears to be altogether a chemical process, and to require for its due explanation and practice an acquaintance with the properties of the elementary bodies, and the laws which regulate their combinations. It is true that many operations of this, as of other chemical arts, have been practised from the most antient times, long before any just views were entertained of the nature of the changes that took place. Mankind, ol. in the rudest and most refined state, have always sought to gratify the love of distinction by staining their dress, sometimes even their skin, with gaudy colours. Moses speaks of raiment dyed blue, and purple, and scarlet, and of sheep-skins dyed red; circumstances which indicate no small degree of tinctorial skill. He enjoins purple stuffs for the works of the tabernacle and the vestments of the high pricst. In the article CALIco PRINTING, we have shown from Pliny that the antient Egyptians cultivated that art with some degree of scientific precision, since they knew the use P. C., No. 539.

of mordants, or of those substances which, though they may impart no colour themselves, yet enable white robes (candida vela) to absorb colouring gs (colorem sorbentibus medicamentis). Tyre, however, was the nation of antiquity which made dyeing its chief occupation and the staple of its commerce. There is little doubt that purple, the sacred symbol of royal and sacerdotal dignity, was a colour discovered in that city, and that it contributed to its opulence and grandeur. Homer marks the value as well as antiquity of this dye, by describing his heroes as arrayed in purple robes. Purple habits are mentioned among the presents made to Gideon by the Israelites from the spoils of the kings of Midian. The juice employed for communicating this dye was obtained from two different kinds of shell-fish, described by Pliny under the names of purpura and buccinum; and was extracted from a small vessel, or sac, in their throats to the amount of only one drop from each animal. A darker and inferior colour was also procured by crushing the whole substance of the buccinum. A certain. quantity of the juice collected from a vast number of shells being treated with sea-salt, was allowed to ripen for three days; after which it was diluted with five times its bulk of water, kept at a moderate heat for six days more, occasionally skimmed to separate the animal membranes, and when thus clarified was applied directly as a dye to white wool, previously pool for this purpose by the action of limewater, or of a species of lichen called fucus. Two operations were requisite to communicate the finest Tyrian purple; the first consisted in plunging the wool into the juice of the purpura; the second, into that of the buccinum. Fifty drachms of wool required one hundred of the former liquor, and two hundred of the latter. Sometimes a preliminary tint was given with coccus, the kermes of the present day, and the cloth received merely a finish from the precious animal juice. The colours, though probably not nearly so brilliant as those producible by our cochineal, seem to have been very durable, for Plutarch says, in his Life of Aiearander, (chap. 36), that the Greeks found in the treasury of the king of Persia a large quantity of purple cloth, which was as beautiful as at first, though it was 190 years old.” The difficulty of collecting the purple juice, and the tedious complication of the dyeing process, made the purple wool of Tyre so expensive at Rome that in the time of Augustus a pound of it cost nearly 30l. of our money.” Notwithstanding this enormous price, such was the wealth accumulated in that capital, that many of its leading citizens decorated themselves in purple attire, till the emperors arrogated to themselves the privilege of wearing purple, and prohibited its use to every other person. This prohibition operated so much to discourage this curious art as eventually to occasion its extinction, first in the western and then in the eastern empire, where, however, it existed in certain imperial manufactories till the eleventh cen

tury.

Being was little cultivated in antient Greece; the people of Athens wore generally woollen dresses of the natural colour. But the Romans must have bestowed some pains upon this art. In the games of the circus parties were distinguished by colours. Four of these are described by Pliny, the green, the orange, the grey, and the white. The following ingredients were used by their dyers. A crude native alum mixed with copperas, copperas itself, blue vitriol, alkanet, lichen rocellus, or archil, broom, madder, woad, nut-galls, the seeds of pomegranate, and of an Egyptian acacia.

Gage, Cole, Plumier, Réaumur, and Duhamel have severally made researches concerning the colouring juices of shell-fish caught on various shores of the ocean, and have succeeded in forming a purple dye, but they found it much inferior to that ...! by other means. The juice of the buccinum is at first white; it becomes by exposure to air of a yellowish green bordering on blue; it afterwards reddens, and finally changes to a deep purple of conside. able vivacity. These circumstances coincide with the ol. nute description of the manner of catching the purple-dye

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Rome for a hundred crow us.

shell-fish which we possess in the work of an eye-witness, Eudocia Macrombolitissa, daughter of the Emperor Constantine VIII., who lived in the eleventh century. The moderns have obtained from the New World several dye-drugs unknown to the antients; such as cochineal, uercitron, Brazil wood, logwood, annatto; and they have |. the art of using indigo as a dye, which the Romans knew only as a pigment. But the vast superiority of our dyes over those of former times must be ascribed principally to the employment of pure alum and solution of tin as mordants, either alone or mixed with other bases; substances which give to our common dye-stuffs remarkable depth, durability, and lustre. Another improvement in dyeing of more recent date is the application to textile substances of metallic compounds, such as Prussian blue, chrome yellow, manganese brown, &c. Indigo, the innoxious and beautiful product of an interesting tribe of tropical plants, which is adapted to form the most useful and substantial of all dyes, was actually denounced as a dangerous drug, and forbidden to be used, by our parliament in the reign of Queen Elizabeth. An act was passed authorizing searchers to burn both it and logwood in every dye-house where they could be found. This act remained in full force till the time of Charles II. ; that is, for a great part of a century. A foreigner might have supposed that the legislators of England entertained such an affection for their native woad, with which their naked sires used to dye their skins in the old times, that they would allow no outlandish drug to come in competition with it. A most instructive book might be written illustrative of the evils inflicted upon arts, manufactures, and commerce, in consequence of the ignorance of the legislature. Mr. Delawal made many ingenious experiments to prove that the particles of dye-stufts possess no power of reflecting light, and that therefore when viewed upon a dark ground they all appear black, whatever colour they may exhibit when seen by light transmitted through them. He hence inferred that the difference of colour shown by dyed cloths is owing to the white light which is reflected from the textile fibres being decomposed in its passage through the superinduced colouring particles. We think it more than probable that this conclusion is in some respects incorrect, and that the aluminous, iron, and tin bases form combinations with dye-stuffs which are capable of reflecting light, independent of the reflection from the fibre itself. There can be no doubt however that this latter reflected light adds greatly to the brightness of the tints, and that the whiter the textile substance is the better dye it will, generally speaking, receive. It is for this reason that scouring or bleaching of the stuffs is usually prescribed as a process preliminary to dyeing. Bergman appears to have been the first who referred to chemical affinities the phenomena of dyeing. Having plungel wool and silk into two separate vessels, containing solution of indigo in sulphuric acid diluted with a great deal of water, he observed that the wool abstracted much of the colouring matter, and took a deep blue tint, but that the silk was hardly changed. He ascribed this difference to the greater affinity subsisting between the particles of sulphate of indigo and wool, than between these and silk; and he showed that the affinity of the wool is sufficiently energetic to render the solution colourless by attracting the whole of the indigo, while that of the silk can separate only a little of it. He thence concluded that dyes owed both their permanence and their depth to the intensity of that attractive force. We have therefore to consider in dyeing the play of affinities between the liquid medium in which the dye is dissolved and the fibrous substance to be dyed. When wool is plunged in a bath containing cochineal, tartar, and salt of tin, it readily assumes a beautiful scarlet hue, but when cotton is subjected to the same bath it receives only a feeble pink tinge. Dufay took a piece of cloth woven of woollen warp and cotton weft, and having exposed it to the fulling-mill in order that both kinds of fibres might receive the same treatment, he then subjected it to the scarlet dye; he found that the woollen threads became of a vivid red, while the cotton continued white. By studying these dif. ferences of affinity, and by varying the preparations and processes, with the same or different dye-stuffs, we may obtain an indefinite variety of colours of variable solidity and depth of shade.

Dye-stuffs, whether of vegetable or animal origin, though susceptible of solution in water, and, in this state, of penetrating the pores of fibrous bodies, seldom possess alone the power of fixing their particles so durably as to be capable of resisting the action of water, light, and air. For this purpose they require to be aided by another class of bodies, already alluded to, which bodies may not possess any colour in themselves, but serve in this case merely as a bond of union between the dye and the substance to be dyed. These bodies were supposed, in the infancy of the art, to seize the fibres by an agency analogous to that of the teeth of animals, and were hence called mordants, from the Latin verb mordere, to bite. However preposterous this comparison is now known to be, the term derived from it has gained such a footing in the language of the dyer that all writers upon his art are compelled to adopt it. Mordants may be regarded, in general, as not only fixing but also occasionally modifying the dye, by forming with the colouring particles an insoluble compound, which is deposited within the textile fibres. Such dyes as are capable of passing from the soluble into the insoluble state, and of thus becoming permanent, without the addition of a mordant, have been called substantive, and all the others have been called adjective colours. Indigo and tannin are perhaps the only dyes of organic origin to which the title substantive can be applied, and even they probably are so altered by atmospheric oxygen, in their fixation upon stuffs, as to form no exception to the true theory of mordants. Mordants are of primary importance in dyeing; they enable us to vary the colours almost indefinitely with the same dye, to increase their lustre, and to give them a durability which they otherwise could not possess. A mordant is not always a simple agent, but in the mixture of which it consists various compounds may be formed, so that the substances may not act directly, but through a series of transformations. The China blue process [CALico PRINTING] affords a fine illustration of this truth. Sometimes the mordant is mixed with the colouring matters, sometimes it is applied by itself first of all to the stuff, and at others both these methods are conjoined. We may dye successively with liquors which contain different substances, which will act differently according to the different mordants successively employed. One solution will give up its base to the stuff only when aided by heat; another acts better and more uniformly when cold, though this is a rarer case. When a mordant consists of a changeable metallic oxide, as of iron or tin, unless great nicety be used in its application, either no effect or an injurious one may be produced upon the dye. All these circumstances prove how necessary it is for the dyer to be thoroughly versed in chemical science. Each of the great dye-works in Alsace, celebrated for the beauty and fixity of their colours, is superintended in the laboratory department by a gentleman who has studied chemistry for two or more sessions in the universities of Paris or some other eminent schools. The numerous complaints which for some time back have been made in foreign markets of the fugitiveness of our calico, but especially of our cloth dyes, ought to rivet the attention of our great manufacturers and merchants on this important desideratum, and to lead them to supply it by consulting qualified persons as to the best means of improving this great branch of national industry. The first principle of dyeing fast colours, we have seen, consists in causing the colouring matter to undergo such a change, when deposited upon the wool or other stuffs, as to become insoluble in the liquor of the dye-bath. The more powerfully it resists the action of other external agents, the more solid or durable is the dye. Generally speaking, a piece of well-dyed cloth should not be unaterially affected by hot water, by soap and water, by exposure to air and light, by dilute nitric acid, or even by very dilute aqueous chlorine. In the following details concerning the art of dyeing we shall consider principally its application to wool and silk, having already treated, in the article CALico PRINTING, of what is peculiar to cotton and linen. The operations to which wool and silk are subj ected preparatory to being dyed are intended, i, to separate certain foreign matters from the animal fibre: 2, to render it more apt to unite with such colouring particles as the dyer wishes to fix upon it, as also to take therefrom a more lively and agreeable tint, as well as to be less liable to soil in use

The matters foreign to the fibre are either such as are naturally associated with it during its production by the animal, such as have been added to it in the spinning and weaving operations, or such as have been accidentally applied. Silk is scoured by means of boiling in soap and water, whereby it is freed from a varnish improperly called gum. This consists of an azotized compound, which may be separated in a gelatinous form by cooling the hot water saturarel with it. It constitutes about a fourth part of the weight of most raw silks, and contains a little colouring matter of an orange or yellow hue. When silk is required to be extremely white, either to be woven in that state, or to receive the brightest and purest dyes, it should be exposed to the action of humid sulphurous acid. [SULPHURAto N.] For dark dyes, silk need not be scoured at all, in which case it preserves its whole weight. Wool is first washed in running water to separate its coarser impurities; it is then deprived of its yolk (a species of animal soap secreted from the skin of the sheep) either by the action of ammoniacal urine, by soap and water, or by a weak lye of carbonate of soda. Common wools lose in this way from 20 to 50 per cent. of their weight, and Merino wools still more. They receive their final bleaching by the fumes of burning sulphur, or by aqueous sulphurous acid. Wools present remarkable differences in their aptitude of combining with dye-stuffs, which depend upon the different structure of the imbrications of the filaments. (Ure's Philosophy of Manufactures, p. 91.) The colouring particles seem to insinuate themselves at these pores with greater or less facility, and to be retained with greater or less force, according to the magnitude and form of the orifices. This difference in dyeing, therefore, is not due to the repulsive action of fatty matter, as has been commonly supposed, since it still exists in wool even when every particle of grease has been removed from it by alcohol and aether. A bran boil is often had recourse to, in order to make wool take the dye more readily and equally; but a hot lye containing onehalf per cent. of crystallized carbonate of soda answers much better. When heated to the temperature of 140° or 150° Fahr., four parts of wool should be immersed in that liquor, and turned about for half an hour. The wool receives a faint yellowish tint from this bath, but it speedily becomes white on exposure to air, or it may be whitened at once by passing it through tepid water containing a very small quantity of muriatic acid. The yellow colour is most probably occasioned by the reaction of the sulphur and iron contained in the wool. According to the experiments of Thenard and Roard, alum combines with wool in the state of a salt, without separation of its acid constituent. Wool boiled with a solution of tartar decomposes a portion of it completely; some of the acid and a little of the tartar combine with the wool, while a neutral tartrate of potash remains in the bath. This fact is interesting in reference to the scarlet dye, showing the important part which tartaric acid here serforms. Tinctorial colours are either simple or compound. 'The simple are black; brown, or dun; blue; yellow; and red; the compound are gray; purple; green; orange; and other numerous modifications, all producible by the mixture of simple colours. We shall treat here of only black and brown, to supply an omission in the previous part of the “Cyclopaedia.’ The other dyes will be discussed in their alphabetical places. Black.-If we apply to a white stuff blue, red, and yellow, in certain proportions, the resulting colour will be black. Proceeding on this principle, Father Castel asserted that 15 parts of blue, 5 of red, and 3 of yellow will produce a perfect black; but in making this statement he was influenced rather by theoretical than practical considerations. In fact he has afforded us no means of procuring these simple colours in an absolute state. It is undoubtedly true, however, that red, yellow, and blue, employed in adequate quantities, will produce black: because they will together absorb, or obstruct the passage of all coloured light, or, in other words, cause its total privation, whence blackness must result. If we suppose a piece of cloth, to which these three colours have been communicated, but not in such proportions as to produce a pure black, we shall have a tint corresponding to the colour that is in excess; as, for example, a blue, violet, red, or greenish black; and with paler tints we shall have a bluish, violet, red, or greenish gray. Gall-nuts, and a salt of iron, so generally employed for the black dye, give merely a violet or greenish gray, and never a

pure black. The pyrolignite of iron, which contains a brown empyreumatic matter, occasions a brown inclining to greenish yellow in light shades, and to chesnut brown in dark hues. By galling cotton and silk, after a bath of pyrolignite of iron, and reiterating the processes several times, a tolerably pure black may be procured. Galls, logwood, and a salt of iron (copperas) produce merely a very deep violet blue; but if they be applied to wool in a hot bath, with frequent exposure to air, the logwood induces a brownness which is favourable to the formation of black. The black dye for hats is communicated by logwood, copperas, and verdigris mixed in certain proportions in the same bath; from that mixture there results a vast quantity of an ochreous muddy precipitate, amounting to twenty-five per cent. of the copperas employed. This mud forms a deposit upon the hats which not only corrodes the fine beaver filaments, but causes both them and the felt to turn speedily of a rusty brown. A well-dyed black hat should retain its original tint as long as it lasts. There is no process in dyeing so defective as that of hats, or which stands so much in need of scientific amelioration. The hatter tries to wash away this ochreous mud by dilute sulphuric acid, and then counteracts the acid by a weak alkaline bath, thus introducing two adventitious evils as remedies for the first and main evil, which a very little chemical science could obviate. Since gall-nuts give a blue precipitate with the peroxide salts of iron, they are occasionally replaced by sumach, bablah, &c.; but account should be taken in this substitution of the proportions of red or yellow colouring matter in these substances, relatively to the tannin which alone forms the blue precipitate. When a black of the best possible shade is to be given, the wool should be first grounded with indigo, then passed through a bath of logwood, sumach, and protosulphate of iron (green copperas). Sumach and nutgalls may also be employed in the proportion of 6 to 24; or the sumach may be replaced by nut-galls, if they be equal to one-third of the sumach prescribed. A good black may be dyed upon an indigo ground with 100 pounds of wool, by taking 200 pounds of logwood, 60 pounds of sumach, 24 pounds of galls, and 20 pounds of green copperas; and giving three heats of two hours each to the wool, with airings between. A good black, without an indigo blue ground, may be given to 100 pounds of wool, by boiling it in a bath of 25 pounds of alum and 674 of tartar; grounding it with weld and madder; then passing it through a bath of 200 pounds of logwood, 60 of sumach, and 2% of galls; taking it out, adding to the bath 20 pounds of copperas; lastly, giving it three heats of two hours each time. The best French black, according to Hellot, may be given to wool by first dyeing it a dark blue in the indigo vat, washing and fulling it; then for every 50 pounds, putting into the copper 8 pounds of bruised galls, and as much logwood tied up in a coarse canvas bag, and boiling them for twelve hours. One-third of the bath thus prepared is to be transferred into another copper with one pound of verdigris, and the wool or stuff is to be worked in this solution without intermission for two hours, the bath being kept hot, but not boiling. After taking out the stuff, another third part of the first bath is to be added along with four pounds of green copperas; the fire must be lowered while this salt is being dissolved, and the bath being refreshed with a little cold water, the stuff is to be worked through it for half an hour, and then aired. Lastly, the residuary third of the first bath is to be now introduced, taking care to squeeze the contents of the bag. From eight to ten pounds of sumach are added, the liquor is just made to boil, then refreshed with some cold water, after which a pound of green copperas being dissolved in it, the stuff is again passed through it for an hour. It is now taken out, aired, washed, then returned to the copper, and worked in the bath for another hour. It is next washed at the river and fulled. A finish is prescribed in the madder-bath. The ordinary proportions used by the English black dyers for 100 pounds of cloth, previously treated in the indigo wat, are about 5 pounds of copperas, as much nut-galls bruised, and 30 pounds of logwood. They first gall the cloth, and then pass it through the decoction of logwood in which the copperas has been dissolved. A finish of weld is often given after fulling; but this is of doubtful utility, especially when a little soap has been used in the fulling-mill. Vitalis prefers the pyrolignite of iron to the ow for 2

the black dye, and says it produces a softer and more velvely colour. We by no means join in this opinion, having found the pyrolignité apt to communicate a brown tint to the blue black, an effect producible also by using old copperas peroxidized by exposure to air. The black dye vat, as it gets exhausted, is employed to dye greys of various shades. š. is dyed black in two methods, according to the market for which it is made. When sold by weight, as was formerly the practice at Tours, and is now with silk thread in this country, it is an object with the dyer to load it with as much colouring or other matter as possible. Sugar is at present much employed to falsify the weight of English silk thread, as any person may discover by applying a hank of it to his tongue. We have seen thread more than doubled in weight by this fraudulent device. Such silk is called English black by the French, who are not suffered to practise this deception. When silk is sold by superficial measure, on the other hand, it becomes the dyer's object to give it a black colour with as little weight of materials as possible. Hence the distinction well known in the trade of heavy and light silks. The 25 per cent of weight which silk has lost in scouring may be in a great measure recovered, by giving it a sufficient dose of galls. For this purpose a bath is made by boiling galls equal to two-thirds or three-fourths the weight of the silk for three or four hours in a sufficient quantity of water, and then letting the decoction settle for two hours. The silk must be steeped in this bath from twenty to thirty-six hours, and then washed in the river. The first galling is however commonly given with a bath somewhat spent; and for heavy blacks generally upon unscoured silk. Several successive immersions in gall-baths, and of considerable duration, are usually given to silk, with intervening washings and wringings at the peg. The silk dyers keep up from year to year a black vat, often of very complex composition. The essential constituents of the vat are sulphate of iron and gum; but many vegetable matters, as well as filings of iron, are usually added. This bath being heated short of boiling, and then allowed to settle for about an hour, the silks are worked in it with much manipulation, occasional wringing out, . and re-dipping. As the copperas and gum get exhausted, the bath must be replenished with these ingredients in due proportions. The addition of logwood and verdigris is ver useful to the black silk dye, and is now generally made. ground of walnut peels is a good and cheap preparation for this dye. W.” have entered into these theoretical and practical details concerning the black dye, as we conceive them likely to prove useful to our cloth manufacturers, many of whom have hitherto followed too much a blind routine. Every wearer of a black coat or trowsers is soon convinced to his cost that great improvements remain to be made in this department of dyeing. II. Brown or dun colour.—This dye is not so common in this country as on the continent, where the colouring matter is generally produced at a very cheap rate by steeping ripe walnuts with their peels in water for a year or two till the vat acquires a deep brown colour and a fetid smell. This infusion affords very agreeable and permanent brown tints without arov mordant, while it preserves the downy softness of the wool, and requires but a simple and economical process. In dyeing with this infusion, a quantity of it proportional to the shade required is to be put into the copper, diluted with water, and made to boil. The cloth or yarn needs merely to be moistened beforehand with tepid water, to be then plunged in the bath, and turned about till sufficiently dyed. Some dyers, however, give the stuff a preparatory mordant of alum, and leave it to drain for twenty-four hours before subjecting it to the bath of walnutcels. p Sumach is usually employed in this country to dye fawns, and some browns; but more beautiful browns may be given to woollen stuffs by boiling them first with one-fourth their weight of alum and some tartar and copperas; washing, and afterwards dyeing them in a madder bath. The shade of colour depends upon the proportion which the copperas bears to the alum. A good brown may also be obtained by mordanting every pound of the stuff with two ounces of alum and one ounce of common salt in a boiling bath; and then dyeing it in a bath of logwood to which some copperas has been added:

or the stuff dyed red in the madder bath may be turned about in the black dye vat till the required shade be hit. The finest browns are produced by boiling each pound of the wool with two ounces of alum, dyeing it in a cochineal bath, and then transferring it into a bath containing a little cochineal darkened with acetate of iron. Instead of cochi neal the archil or cudbear bath may be used with a little o or galls. This forms a cheaper but a more fugitive Colour. A beautiful brown tint, on wool or silk, may be had by first giving a pale blue shade in the indigo vat, then mordanting with alum, washing and finishing in a madder bath till the proper brown be brought up. The Saxon blue vat may also be used. If the stuff be mordanted with alum and tartar, then boiled in a madder bath, afterwards in one of weld or fustic, to which more or less copperas has been added, we shall have a mordore, cinnamon, or chestnut brown. By the combination of olive shades with red, bronze tints may be produced. For twenty-five pounds of stuff a bath containing four pounds of fustic will suffice. Boil the wood two hours, then turn the stuff in the bath for an hour, take it out, and drain. Add to the bath four or six ounces of copperas and a pound of madder or sandal wood ; then work the stuff in it till the wished-for shade is attained. Silk may receive a ground of annatto, and then be dyed in a bath of logwood or Brazil wood, whereby a fine brown tint is obtained. : Catechu is used for giving a bronze and brown to cotton goods. [CALIco-PRINTING..] Blue colours are dyed with indigo, Prussian blue, and woad. Yellows with fustic, Persian berries, quercitron, turmeric, and weld. Reds, with archil or cudbear, Brazil wood, cochineal, kermes, lac, logwood, madder, safllower, or carthamus. The purple, green, and orange dyes may be conveniently considered under the heads of ScARLET DYE, INDIGo, and QUERCITRoN. We shall conclude this article with a few practical remarks. M. Roard, long the skilful director of the Gobelins' dyeworks, has observed that copper boilers exercise a considerable influence upon delicate dyes. He found that ammonia causes a blue precipitate in the alum bath made in such boilers, while it causes merely a white precipitate in the same bath, made in vessels of glass, porcelain, and tin. When wool is kept for some hours in boiling-water contained in a copper vessel, it acquires a greenish gray tint; a result increased by the ordinary mixture of alum and tartar. If into this bath white wool be plunged, it receives a greenish yellow, or sometimes an ochrey hue. These observations of M. Roard are of considerable importance, and should lead dyers to employ tin or at least brass boilers instead of copper ones for all vivid colours. Heating with steam, either by double vessels, by straight or spiral tubes, ‘. on all occasions to be preferred in the dye-house to naked fires, which seldom fail to carbonize some portions of the vegetable or animal matters, and thereby to degrade the colours. The top edge, or surface of the boilers should be about three feet and a half above the floor; this being a height which the workmen find most convenient for their manipulations when they stand upon a step 8 or 10 inches high. The stuffs mordanted with alum should not be transferred to the bath immediately, but be allowed to drain and air for 24 hours. The colours are thereby rendered more lively than when dyed soon after the aluming. As experience has proved that an old alum bath is better than one fresh made, it should not be thrown away, but be strengthened or refreshed by the requisite additions of alum and tartar. It is certain that wools boiled in alum the second time, are more beautiful than those boiled in it the first time. DYER, JOHN, born in 1700, was the second son of a respectable solicitor of Aberglasney in Caermarthenshire. He received his education at Westminster school, and when that was completed, began the study of the law. An early taste for poetry and painting led him to relinquish his legal pursuits, and he travelled about South Wales in the capacity of an itinerant painter. At this period he wrote his poem ‘ Grongar Hill,’ which was published in 1727. Though he seems to have made but small proficiency in painting, he went to Italy to study, where he wrote the “Ruins of Rome,’ a descriptive poem, published in 1740. On his return to

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