Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/140

 O C H

O C H

Alum, and vitriol alone, require no fuch additions, the firft of thefe containing a very large quantity of an alkalious, white earth, as the other does of an ochrcous yellow one. OCHRES, in natural hiftorv, the name of a large genus of earths, ufed principally by the painters. The mull com- mon kinds are either yellow, or red, 'though there are brown, blue, and green ochres, and a number of diftinft fpecies of all thefe colours. Of the yellow ochres, Dr. Hill, in his hiftory of fulfils, defcribes eleven fpecies. Of the red, the fame number. Of the brown two. Of the blue, and green, one fpecies each ; and of the biack, two. The greater number of thefe are, or have been, at one time, or other, in ufe in painting, in different parts of the world. Some, however, there are, efpecially of the yellow and red kinas, which that author has, himfelf, difcovercd in different parts of our own, and other kingdoms, which are worthy the tryals of the perfons concerned in that branch of trade, as they have already been proved, at his requeft, in fmall quantities, and found to anfwer very well,
 * 1) ///'a Hift, of Fofii p. 51.

The fpecies ef the yellow ochres are thefe: 1. The ochra Uviffima,friabiru,pallldijfme fiavefcens ; or very light friable pale yellow ochre. An earth found of late years in Penfylvania, Virginia, and fome other of our American plantations, which has been tried both in water, and oil, and makes a very pale ftraw colour in the former, and a fine yellow, though fomewhat deeper, in the latter ; but making no good colour, when burnt,

2. The ochra pondcrofa, dura, palllde fiavefcens ; the hard, heavy, pale, yellow ochre. This is found in Germany, Sax- ony, France, and England, and is well known to the painters, and much ufed by them for a pale yellow. They call this French ochre ; but it is dug in confiderable quantities in Dor- fctfhire. This makes but a dull colour, when burnt, and is, in it)* native ffate, much inferior to the common kind.

3. The ochra lcviff?na,fiava, frlabilis ; the light, crumbly, yellow ochre. This is frequently thrown out at the mouths of chalybeate fprings, and, fometimes, from fuch as are not manifeltly impregnated with the particles of that metal ; and is found in great abundance on Hampftead heath. This is not ufed by the painters, but is a bright yellow, and very fine, and is, therefore, worth trying.

4. The ochra levis, aurea, friabiiis ; the light, friable, gold- coloured ochre. This was the ochre of Theophraftus, and of the earlieir. ages we have accounts of. It is common in our gravel pits, in large loofe lumps. The painters of the prefent age are not acquainted with this ; but it is a very valuable fubftance, making a fine ftrong yellow in its na- tive ftate, and a very bright, and beautiful red, when burnt. Hill's Hilt, of FofT p. 52.

5. The ochra crocea, laminata, levis ; the light, plated, faftron- coloured ochre. This was alfo well known to the an- tient painters, though not fo early as the former, and is the Attic, or Athenian, ochre of Diofcorides. It is, like the for- mer, common in fmall plated mafTes, in our gravel pits, and, though not known to our prefent painters, has been tried, and proves a very fine yellow, both in water, and oil, in its native ftate, but does not make a bright red, on burning. Hill's Hift. of FofT p. 53.

6. The ochra pondcrofa, fiava, friabiiis ; the heavy, friable, yellow ochre. This is common in England, and is well known, and very much ufed in its native fiate among the painters. It is dug in Buckinghamfhire, Somerfetfhire, and Oxfordshire, but is greatly inferior to the two former kinds. Hill's Hift. of FofT. p. 54-

7. The ochra argillacea, pondcrofa, luiea, dura 5 the hard, hea- vy, clayey, yellow ochre. This is dug in Buckinghamshire, Yorkshire, and fome other counties, and is fentupto Lon- don, and ufed" by the painters, making a very lively yellow in its native ftate, and a pleafant, though not a ftrong red, when burnt. Hill's Hift. of FofT. p. 55.

H. The ochra duriffvna, pondcrofa, fiava \ the ftony. hard, and heavy, yellow ochre. This is well known to the painters, and much valued by them. It is dug in Buckinghamfhire, Staffordshire, and Yorkshire, but moft plentifully in Oxford- fliire, whence it is continually fent up in gyeat quantitiesto London. It makes, in its native ftate, a fine yellow, and, when burnt, a very beautiful red, and is the fort ufed for burning into red ochre in the colour-Shops.

9. The ochra argillacea, fordid:: fiavefcens ; the dull, dufky, yellow, clayey ochre. This is dug in Buckinghamfhire, Staf- fordshire, and Oxfordshire, and is fent up to London, and ufed in the coarfer mixtures at the colour-Shops, in its na- tive ftate, but, when rightly managed, it burns to a very fine valuable red. This, and the former, and fome other of the before-mentioned, conta ; n in them a conftderable quantity of a genuine clay, and thence are more compact and ftifF than the more pure kinds.

10. The ochra argillacea, hiteo-fufca levis ; the brownifh, yellow, light, clayey ochre. Tins is common in Bucking- hamfhire, Northamptonshire, and many other counties, and though not fo florid in its colour as many other ochres, yet makes a very pleafing paint, and has what the painters call a good body. This is not yet known among the painters, but

4

is worth tfcelr being acquainted with. Hill's Hift. of FofT

p. 56.

11. The laft is the ochra pondcrofa, frlabilis, aureo-crocea,

commonly called gialldlno, and by our painters Naples yellow.

See the article Giallolino.

The fpecies of the red cchres arc the following : 1. The

ochra rubra friabiiis ponder of a, qua fd Syricum antiquorum j

the red, heavy, friable ochre, the Syrian fd of the antients.

See the article Sil.

2. The ochra purpurea^ friabilh alkalina, qua almagra recen- tiorum, fil Atticum antiquorum ; the friable, purple, alkaline ochre, the ahmgra of the moderns, and Attic fil of the antients. See the artcles Sil, and Almagra.

Thefe are both ufed at this time in painting, and the latter alfo in medicine. The firft of them is common in many parts of England ; the latter feems peculiar to Spain.

3. The ochra purpurea ponder oftjfima dura; the hard, heavy, purple ochre. This is well known among the painters, and called by them Indian red, and by Lemery terra perfica. It is dug In the ifland of Ormuz, in the Perfian gulph, and thence is difperfed over all the Eaft-Iiidies. There is alfo fome of it dug about Bombay. It is ufed both there, and with us, as a fine red in painting. Hill's Hilt of FofT p. 58.

4. Ochra frialilis floride rubefeens ; the bright red, friable ochre. This is much efteemed in painting in many parts of the world, but is lefs known in England than in any other of the European nations. It is dug in vaft quantities in the country above Bengali, and is ufed by the painters in France and Germany, as a fine red. It would be wor- thy our traders in thefe commodities better acquaintance Hill's Hift. of FofT. p. 59.

5. The ochra friabiiis pallide rubefeens, qua bolus Veneta vul- go ; the pale red friable cchre, commonly called Venetian hole. See the article Veneta bolus.

6. The ochra friabiiis levis, pallide rubefeens, alhalina j the light, friable, alkaline, pale, red ochre. This is a very fine, and valuable earth, at prefent unknown in painting, but ve- ry eafy to be had, and worthy the bringing into ufe. It is thrown up in digging in our American plantation's, and proves, on tryal, to be a bright and fine colour in oil. Mill's Hift. of FofT p. 60.

7. The ochra argillacea palMJime rubefeens ;Jthe pale red, clayey, ochre. This is a fubftance yet unknown to the world, but produced in great plenty in Penfylvania, and Virginia, and will, at leaft, fupply to thofe countries all the purpofes of the Englifh. reddle.

8. The ochra purifftma levis pvrpurafcens ; the fine, light, purple ochre. This is a fubftance common in many parts of England, but not yet univerfally known among our painters. They often ufe it, indeed, without knowing what, or whence, it is ; fome conftderable quantities of it having, at times, been fent to London, from the foreft of Dean in Gloucefterfhire, and one or two of the colour-men engrof- fing it to themfelves, and felling it, when prepared, under the name of Indian red, the third fpecies of red ochre., to ■ which it is, at leaft, equal in beauty of colour.

9. The ochra purpurea pmderofa purifftma, qua rubrica fine- pica antiquorum; the fine, heavy, purple cchre, the rubrica fino- pica of the antients. See Sinopica rubrica.

10. The Ochra argillacea indurata rubra, qua Creta rubra auilorum ; the indurated, clayey cchre, called red chalk. See the article Chalk.

And the nth, and laft, the ochra faxea rubra, qua fil mar- morofum antiquorum ; the red, ftony ochre, the marbly fil of the antients. Hill's Hift. of FofT p. 62. See the article Sil. The fpecies of brown ochres are only two ; the firft is, what the painters call umber; and the fecond what they call Co- fagn earth. See the articles L t mekr, and Cologn earth. The blue, and green, are the fubftanccs called lapis armenus, and bergruen, which fee under the articles Armenus lapis, and Bergruen.

Of the black ochres there are, laftly, two fpecies ; the firft of thefe is tha ochra friabiiis, pmde-ofa, nig'-efeens ; the heavy, friable, black ochre. A very fine, and valuable earth, worthy to be brought into ufe among the painters, though, at prefent, unknown to them. It is found in perpendicular fiflures of the ftrata of ftone in Leicefterfhire, and fome other counties of England, and would make a very fine black, ei- ther in water, or oil. Hill's Hift. of FofT p. 65. The fecoud is the pfeudo cchra levis, nigrefcens, qua Creta ni- gra piclorum; the light, black, baftard ochre, called black chalk. See the article Chalk.

Thefe are the feveral fpecies of ochres at prefent known; and it is very plain, from this fhort account of them, that both our own country, and our plantations abroad, contain many treafures of them, the value of which is yet unknown. Dr.Lifterobferves, that ochreous earths are Separated in greater or lefs quantities, from all the medicinal fprings of England, and it is to thefe, and the nitrous and muriatic ialts, tha^ they all owe their virtues. The ochre they contain is ufually of the nature of that which our painters, to diftinguifh it from the yellower kind, call brown ochre. This is produced from the iron ores that are met with in the way of the current of

thefe