MANUFACTURES.

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Manufac- In England, where, at that time, it appears that•ures. woad was not cultivated, the first mention of indigo inthe laws occurs in the year 1581, under the reign ofElizabeth; not, however, on account of a blue but ablack dye. No woollen cloths were to be dyed blackwith the nutgall, madder, and other materials, till theyhad received the first ground, or been rendered blue bywoad, or woad and indigo together ; the consequence ofwhich law was an increase in the consumption of indigo;and from that time the use of indigo has gradually in-creased in this Country, and now forms a very importantarticle of commerce, producing a revenue of upwards of£ .£30,000 per annum.

°f (603.) Culture of indigo .—In the cultivation of thiskplant, one of the most i mportant points to be attended to is,to have the ground thoroughly drained and cleared fromweeds. The soil should be fine and rich, and theclimate warm; and the season of sowing should berainy, as the earth must either already have imbibedwater, or rain must speedily follow the sowing, otherwisethe seed becomes heated and rots, and all the labourspent upon it is of course lost. The ground being pre-pared, a number of slaves ranged in a line inarch acrossmaking little trenches of the width of their hoes, andtwo or three inches deep, and about a foot distant fromone another every way ; then returning, they drop someseeds in each trench, and afterwards cover them with theearth taken out.

During the process of vegetation the ground must becarefully weeded, in order to prevent any mixture ofherbs, which would injure the indigo in its manufacture.In moist weather the plant comes up in two or threedays, and in about two or three months after it is fit forcutting. If suffered to run until it runs into flower, theleaves become too dry and hard, and the indigo obtainedfrom them proves less in quantity and less beautiful:the due point of maturity is known by the leaves begin-ning to grow less supple or more brittle. . In rainyseasons, the cutting may be repeated every six weeks:cutting in dry weather kills the plant; but if that isavoided, one plant will continue to afford fresh crops fortwo years.

The manner in which it is commonly prepared is asfollows: a large quantity of the herb is put into a vator cistern of strong mason-work, with so much water asis sufficient to cover it, and some wood is laid above toprevent it rising up. The matter begins to fermentsooner or later, according to the warmth of the weatherand the maturity of the plant, sometimes in six or eighthours, and sometimes in not less than twenty. The liquorthen grows hot, throws up a plentiful froth, thickensby degrees, and acquires a blue colour, inclining tov iolet, and in proportion as the heat increases, azote is dis-engaged, the vegetable is decomposed, and the mixtureabsorbs oxygen ; the fermenting fluid passes from agreen to a violet tinge, and this by degrees changes toa blue colour. The great art of the manufacturer is tocheck the fermentation at a proper degree ; for if it ischecked too soon, the plant remains impregnated withmuch essential salt, which diminishes the quantity ofindigo; and if allowed to remain too long, the tenderextremities of the plant undergo a putrefaction whichdestroys the beauty of the colour. Some years ago,a method of invariably ascertaining the correct fermen-tation of the indigo was published at St. Domingo,wnicn consisted in writing on white paper with thematter to be examined, and if the ink be of a very

high colour it is a proof that the fermentation has not Mechanicalarrived at its true point. The experiment is repeated Processes,every quarter of an hour, until it is perceived that theliquid has lost its colour, which is said to be a verycorrect method of ascertaining the proper degree offermentation. Others pour a quantity of the liquidinto a silver cup, which they shake until the grains aredeposited, and judge by the quality of them the properstate of fermentation. When the feculent particles beginto be precipitated to the bottom of the cup, it is thenjudged that the herbs have attained the true degree ofmaceration to obtain indigo. Five or six minutes afterthe liquid has been put into the cup, it is perceived toform round its edges a cordon of feculte or sediment, atfirst of a green colour and then blue. When the mace-ration is not at the requisite point, the cordon or girdledetaches itself with difficulty from the sides of the cup,but finally precipitates, and the water above it becomeslimpid, although of a yellowish hue. When these signsare perceived, they infallibly indicate the success of thefirst operation.

The liquid impregnated with the tincture is then letoff by cocks in the bottom of the vessel into another vatplaced for that purpose, without disturbing the herb.

In the second vat the liquid is strongly and inces-santly beaten and agitated with a kind of bucket fixed to apole, until the colouring matter is united into a body.

A good deal of nicety is required in this operation also,for if the beating ceases too soon, a part of the colour-ing matter remains dissolved in the liquid; and, if con-tinued too long, a part of that which had separated isdissolved afresh. The exact time for discontinuing theprocess is determined by taking up some of the liquoroccasionally in a little cup, and observing whether theblue fecula is disposed to separate and subside.

The whole being now suffered to rest until the bluematter has settled, the clear water is let off by cocks atdifferent heights in the sides of the vat, and the bluepart discharged into another vat by the cock at thebottom. Here it is suffered to settle for some timelonger, then further drained in cloth bags or sacks, andexposed in shallow, wooden boxes to the air, withoutadmitting the sun, and carefully keeping it from the raintill thoroughly dry.

Before it is quite dry, it is cut into small pieces of aninch square, which may be detached readily from thebox when it is quite dry. Yet, however well dried anddrained the indigo may be, it always experiences in thefirst month of its fabrication a considerable diminutionof quantity. It is packed for commerce either inbarrels or in sacks of coarse linen, covered with ox-hides, so perfectly sewed together as entirely to ex-clude the air. These packets are called “ ceroons ; theyare much preferable to barrels, as they are more solidand more conveniently transported from one place toanother.

Indigo is commonly divided, from the colour it ex-hibitswhen broken, into three kinds, viz. copper-coloured,purple, and blue. These different appearances probablydepend upon the different methods of preparing theindigo used by different manufacturers, upon the age ofthe plant, which greatly influences the appearance of theindigo, or upon the time at which the plant is gathered.

The superiority of some ot the indigoes of the EastIndies over those of America is said to proceed from theleaves of the plant being alone employed and the twigthrown away. Some heat the water in the steeping