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Ms in there not being above fix Pounds of Indigo to a Ba] of Paftel,when the Paitel begins to cafi its blue Flower ; and in its not being heated for Ufe above twice. Thus blued, the Stuff is boil'd with Alum, or Tartar, then madder'd ; and, laftly, the Slack given with Galls, Copperas, and Su- mac : To bind it, and prevent its fmeering in Ufe, the Stuffs are well fcower'd in the Fulling Mill, when white, and well wafh'd afterwards. For Stufts of lefs Value, 'tis fufficient they be well blued with Paftel, and black'd with Galls and Copperas : But no Stuff can be regularly dyed from White into Black, without palling thro the intermedi- ate Slue. Yet there is a Colour call'd cold Slack, or Je- fuits Slack, prepar'd of the fame Ingredients as the for- mer, but without being firft dyed Slue. Here the Drugs are diflblv'd in Water that had boil'd four Hours, and flood to cool till the Hand wou'd bear it ; then the Stuff dipp'd in it, and again taken out fix or eight times. Some prefer this Slack to the other, but on weak grounds. This Me- thod of fDying Slack is faid to have been invented by the Jesuits, and to be flill pracYis'd in their Houfes, where they retain Numbers of iDyers. See Gray. See alfo Dying.
German or Fra?ikfort Black is made of the Lees of Wine burnt, then wa/h'd in Water, and ground in Mills for thatPurpofe, together with Ivory or Peach-Stones burnt. This Slack makes the principal Ingredient in the Rolling- Prefs-Printers Ink. It is ordinarily brought from Frankfort, Mentz, or Strasbourg, either in Lumps, or Pouder. That made in France is lefs valued than that of German}', by reaibn of the Difference between the Lees of Wine ufed in the one and the other ; tho 1'ome prefer that made at 'Pa- ris to that of Frankfort.
Ivory or Velvet Black, is made of Ivory burnt, ordinari- ly, between two Crucibles well luted 5 which being, thus, render'd perfectly black, and in Scales, is ground in Water, and made into Troches, or little Cakes, us'd by the Pain- ters ; as alfo by tho Jewellers, to blacken the Bottom or Ground o'- their Collets, wherein they fct their Diamonds to give 'em their Teint ot Colour.
Sfanifh Black, fo call'd becaufe firft invented by the Spaniards, and moft of it brought from them, is no other than burnt Cork ; ufed in various Works, particularly a- mong Painters.
Zamf-BziCK, or Smokc-BihcK, the Smoke of Rofin, prepar'd by melting and purifying the Rofin inlronVef- lels ; then fetting fire to it under a Chimney, or other Place made for the Purpofe, and lined a-top with Sheep- Skins, or thick Linen Cloth, to receive the Vapour, or Smoke, which is the Slack : In this manner they prepare vaft Quantities of it at 'Paris. In England it is, ordinarily, prepar'd from the refinous Parts of Woods, burnt under a kind of Tent, which receives it: It is ufed on various Occa- sions, particularly in the Printers Ink ; for which it is mix'd with Oils of Turpentine and Linked, all boil'd together. It muft be obferv'd, that this Slack takes fire very readily, and, when on fire, is very difficultly extinguifh'd : The beft Method of putting it out is, with wet Linen, Hay, or Straw ; for Water alone won't do it.
Earth-B-LACX. is a kind of Coal found in the Ground, which, well pounded, is ufed by the Painters in Frefco.
There is alfo a kind of Black made of Silver and Lead, ufed to fill up the Strokes and Cavities of Things engrav'd.
BLACKNESS, the Quality of a black Body, or a Co- lour arifing from fuch a Texture and Situation of the Su- perficial Parts of the Body, as docs, as it were, deaden, or rather abforb, the Light falling on it, without reflecting any, or very little, of it to the Eye. In which Senfe Slack- ness flands direftly oppofed to Whitenefs ; which confifts in fuch a Texture of Parts, as indifferently reflefts all the Rays thrown upon it, of what Colour foever they be. Sir Ifaac Newton, in his Of ticks, fhews, that for the Produc- tion_ of black Colours, the Corpufcles muft be lefs than thole which exhibit any other Colours 5 becaufe, where the Sizes of the component Particles are greater, there is too much Light reflected to conftitute this Colour ; but, if there be a little lefs than is requifite to reflect the white, and vety faint blue of the firft Order, they will reflea fo little Light, as to appear intenfely black ; and yet may, per- haps, refleft it varioufly to and fro within them fo long, till it happen to be ftifled and loft; by which means they will appear black, in all Pofitions of the Eye, without any Transparency. And from hence it appears why Fire, and Putrefaaion, by dividing the Particles of Subftances,' turn them black ; why fmall Quantities of black Subftance's im- part their Colours very freely, and intenfely, to other Sub- ftances to which they are applied ; the minute Particles of thefe, by reafon of their very great Number, eafily over- fpreading the grofs Particles of others : Hence alfo appears, why Glafs ground very elaborately with Sand, on a Cop- per-Plate, till it be well polifh'd, makes the Sand, toge- ther with what by rubbing is worn off from the Glafs and Copper, become very black ; and why black Subftances do, fooneft of all others, become hot in the Sun's Light, and
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burn, (which Effea may proceed partly from the Multi- tude of Refraaions in a little room, and partly from the eafy Commotion of fo very fmall Particles 5 ) and alfo why Slacks are ufually a little inclined towards a bluifh Co- lour : for, that they are fo, may be feen by illuminating white Paper, by Light refteaing from black Subftances, where the Paper will ufually appear of a bluifh white; and the Reafon is, that black borders on the obfeure blue of the firft Order of Colours; and therefore, refleas more Rays of that Colour than of any other. It is neceffary al- fo, to the Produaion of Slacknefs in any Bodies, that the Rays be ftopp'd, retain'd, and loft in them ; and thefe conceive Heat (by means of a Burning-Glafs, f£c.) more eafily than other Bodies ; becaufe the Light which falls upon them is not refleaed outwards, but enters the Bo- dies, and is often reflea:d and refraaed in them, till it be ftifled and loft. See Light and Colour.
BLACK ROD, or Gentleman-Ufher of the Slack Rod, is Chief Gentleman-Uftier to the King : He is call'd in the Slack Book, Lator Virge Nigra: Si? Hofiiarins, and elfe- wherc Virgi-Safulus. His Duty is to bear the Rod before the King at the Feaft of St. George at Wmdfor : He has alfo the keeping of the Chapter-Houfe Door, when a Chap- ter of the Order of the Garter is fitting ; and, in time of Parliament, attends the Houfe of Peers. His Badge is a Slack Rod, with a Lion Gold a-top. This Rod has the Authority of a Mace. The Office was formerly held by Patent.
BLACKS, or Negro's, a Nation of People, fo call'd from the Colour of their Skin : For the Reafon of their Colour, and the Commerce made with 'em, fee Negro.
BLADDER, in Anatomy, a thin expanded membranous Body found in feveral Parts of an Animal, ferving as a Re- ceptacle of fome Juice, or of fome liquid Excrement; from whence it takes various Denominations, as Urinary-Slad- dcr, Gall-Sladder, &c.
Bladher, by way of Eminence, isalargeVeffel, which ferves as a Receptacle of the Urine of Animals, after its Secretion from the Blood in the Kidneys. It is fituated between the Duplicature of the Peritoneum, and the lower Part of the Abdomen, between the Os Sacrum and the Os Pubis, above the ftrait Gut in Men, and in the Neck of the Womb in Women. It is tied to the Navel by the Urachus degenerated into a Ligament, its Sides to the Umbilical Arteries, and its Neck to the Inteftimtm ReSum in Women. It is compos'd of three Coats ; the firft a Covering of the Peritonaeum ; the fecond is compos'd of Mufcular Fibres, which run ir- regularly feveral ways; and the third, which is full of Wrinkles for facilitating its Dilatation, is both glandu- lous and nervous. Its Glands feparate a vifcous and flimy Matter, which defends it from the Acrimony of the Salts in the Urine : Around its Neck there goes a fmall Mufcle, call'd SphinBer Vejicie, which contraas the Orifice of the Sladder, to prevent the Urine from dripping involuntarily, or till it thruft open the Paffage, by the Contraaion of the fecond Coat of the Blader, which is therefore call'd Ztera- for Urine. The Sladder has Blood- Veffels from the Hy- fogafiricks ; and Nerves from the Inter coflak. See U-
RINE, &C.
BLAIN, a Diftemper incident to Bcafts, confifting in a Bladder growing on the Root of the Tongue againft the Wind-Pipe,which at length fwelling, (lops the Wind. It comes by great chafing, and heating of the Stomach ; whereby, as iomejudge, it ftill grows, and increafeth by moreHeat.
BLANCHING, the Art or Manner of Sleaobing, or Whitening. See Bleaching.
Blanching of Wax. See Wax.
Blanching, in Coinage ; the Preparation of the Pieces, given 'em before the ftriking, to give 'em the Luftre and Btillant. The Stanching, as now praBis'd, is perform'd by heating the Pieces in a kind of Peel, with a Wood Fire, in manner of a Reverberatory, fo as rhe Flame paffes over the Peel. The Pieces being fufficiently heated, and cooled again, are put lucceffively to boil in two other Peels of Cop- per, wherein are Aqua fortis, common Salt, and Tartar of Moutpellier ; when they have been well drain'd off this firft Water in a Copper Sieve, they throw Sand and frefh. Water over 'em ; and when dry, they are well rubb'd.
The antient Method of Stanching was, by putting the Pieces, after heating, in a large Veffel of common Water, and fome Ounces of Aqua fortis ; but in different Propor- tions for Gold and Silver. This Method is now difus'd, partly by reafon of its Expenfivenefs, and partly becaufe it diminifhes the Weight of the Metal. See Coining.
BLANK VERSE. See Verse and Rhyme.
BLATA BIZANTIA, or Unguis Odoratus, the upper Part of a Shell call'd by the Latins Conchy Hum, Thefe Shells are of different Magnitudes ; but the Figure, in all, is that of a Claw of a Wild Beaft ; whence its fecond Name } the firft being occafion'd by its being ufually brought from Confiaminofle, the antient Siztouium. The Slata Sizan-
tia
