Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/373

 ROB

liquor let out of the cooler is boiled up again, and flioots

more alum. .,,, c ..,

ROAD goofe, in zoology, the name of a (mall fpecies of wild

goofe. See the article Goose. ROAN, in the manege. A roan horfe is one of a bay, forrel, or black colour, with grey or white Spots interfperfed very thick- when this party-coloured coat is accompanied with a black head and black extremities, he is called zrean with a black-a-moor's head. And if the fame rmxturc is predo- minant upon a deep forrel, it is called claret roan. ROASTING, in metallurgy, is the Separation of volatile bo- dies from thofe which are more fixed by the combined action of air, and fire; and is generally the firft procefs in the feparation of metals from their ores; it differs from fublimation only in this, that in this operation the volatile parts are dimpated, when refolved into vapours; whereas in that they are preferved.

Sulphur and arfenic are in this manner collected and pre- • Served in the roajiing of many ores; and fublimation made, as it were, occasionally in the procefs.

The feparation of the volatile parts of bodies, from the more fixed is, however, in many cafes very difficult, and much nicety is required in the conducting this operation; this is the cafe, for inftance, when the whole compound body melts in almoft the fame degree of fire that is neceflaryto raifu, and dimpate the volatile parts 'in the air; in filch cafes, care muff be taken, firft: previoufly to pound a little the body to be roajled, that its furface contiguous to the air may be increafed in extent. A gentle fire is alfo neceflary on fuch occafions, and a very free accefs of the air, which is the vehicle of thefe vapours. When the body in the roajiing grows on thefe occafions into large lumps or clots, the furface of it mult be reftored to the necefiary extent, by repeated poundings, for it is necefTary above all things, that the matter be kept extended and recent, and never collected into a heap.

Bodies the moil refractory in the fire, are always the moft cafily roajied; for a great fire may be confequently kept up to fuch, nor need the operation be repeated fo often. Care rrruft always be taken, however, that while the volatile bo- dies arc diffiparing in the fire, they do not carry up with them fomething from the fixed ones alfo; for this is a dis- advantageous accident, and too often happens, efpecially when a fire too violent is ufed in the beginning of the opera- tion; to prevent this, it is fometimes neceflary to add fome fixing body to the mafs. Cramer's Art of Foff. p. 189. The bufmefs of roajiing of ores of metals, as now ufually pradtifed, is fubject to many inconveniences, which may be moft of them eaftly remedied, and the whole bufmefs re- duced to a few eafy rules, t. The roajiing of ores mould be always, performed, without addition, when the ores are rich, or of itfelf merely of a metallic nature. But the ad- ditions of quicklime, potafhes, iron filings, and the like, are necefTary, when arfenical, antimonial and fulphureous matters are found to be mixed with the ores. 2. The fire is to be fo regulated from the fi*fr, that only the lighter or jpore volatile fulphureous or arfenic fumes may fly off, otherwife the more metallic part would likewife go, and without fome contrivance to catch it would be loft. The ore muff, however, always feel the force of an open flame, otherwife the Sulphur, arfenic, &c. will never be thoroughly diflodged. 3. The more thefe immature fub- ftances abound in ore, the gentler the fire fhould be at firft and when the greater part of the fulphureous matter is thus exhaled, the fire is then to be quickened. 4. Where fuch additions are ufed, as arc not metalline, as lime, mud, pot-afh, &c, they ought always to be feparated after wards from the matter before the fufion, by waffling. Shaw's Lectures, p. 251. ROB, (Civ/.) in pharmacy, the infpiffated juice of any fub- ftance, ufually boiled up to the confiftence of honey. It is poflible, that great improvements might be made, by introducing the ufe of this form among the malt diftillers. The great inconvenience attending that art being, that the malt being of a large bulk, in proportion to its faccharine part, and requiring a large proportion of water to extract that faccharine part, many large veffels, fuch as main tubs, coolers, fermenting back.;, 6v, are necefiary; and the necefTary labour on the Subject is increafed, and the com- modity rendered dearer. The remedy of this fhould Seem, the introducing a new art fubfervient to that of the malt diftiller, and confining itfelf to the boiling down of malt wort to art*, fo as to Supply the malt {filler with his fubject, in the fame manner as the fine {tillers are Supplied with treacle by the Sugar baker. By this means the bufmefs of the malt Stiller would be reduced to a great degree of Sim- plicity, and the Spirit produced would be alSo much finer than at prefent, becaufe the Subject would come tolerably refined to his hands, and purged of its grots, mealy and hufky matter, which yields a difagrceable oil in diftillation, and is alfo apt to burn to the ftill,a:id Spoil the Spirit. It is pof- Sible that a Spirit purer and finer than that from treacle might this way be procured from malt prudently managed. lb. p. 219. ROBALO, in zoology, a name by which fome have called die Mmuri an American fea fiih of the lupus marinus, or

ROC

baftl- kind, m&tgb&fs Hift. Pifc. p. 272. Sc-c &&&£.

ROBBINS, in a Ship, Small lines which make the &il fait to the yards, being reeved into eylet holes in the fail under the head-rope for that purpofe. The word is make fajl the Rabbins : Sor at Sea they don't fay tie, but make faff.

ROBERSMEN, or Roeerdsmen', in our old writers, a fort of great thieves, mentioned in the ftatutcs, 5 Ed. 3. c. 14, And in Rich. 2. c. 5. Sir Edward Coke fays, that Robin Hood lived in the reign of Rich. 1 . oh the borders of England and Scotland by robbery, burning of houSes, ra- pine and fpoil, &c. And that thefe rderdfmm took their names from him. 3. Lift. 197. Blount, Cowel.

ROBIAHerba, in Botany, a name given by Paul us Mg\- neta, and many others to a plant ufed in dying. The near refemblance of the name to the word ruhia, has made many conclude that it was the mbia, or madder which they meant by it, but they have taken care in their writings to diftinguiffi it from that plant, and it is plainly the gmiftella tin£ioria, or dyers weed, 1 " that they meant by the robia kcrba. They fay it was ufed to dye yellow, and that it was alfo a cuftom to ftain the hair with it. Thefe are the properties recorded of the cymene and escomenimn of the Gieeks, and latum or lutcahcrba of the Latins, which were names of the genijtella tinSloria. Pliny fays, that the lutttm had leaves like flax and flowers like broom, which is exactly the cafe with the gemjlelia tinc- foria, but by no means agrees with the glaff um or woad-

ROBINIA, in botany, the name of a genus of plants, called pfeudo-^cacia by Tournefort, and the generality of authors. The characters are thefe j the pcrianthium is Small and one leaved, it is divided into four fegments at the end, the three under fegments are very narrow, but the upper one four times as broad, tho' of the fame length with the reft, and is {lightly emarginatedj the flower is of the papilionaceous kind. Thevexillum is large, round and obtufe. The alee are of an oblong oval figure, and ftand free, having a very ihort obtufe appendage : the carina is nearly of 1 a femiorbicular figure, it it compreiled, obtufe and of the fame length with the ala?. The ftamina are diadelphous filaments pointing upwards. The anthers are roundifh. The germen of the piftill is oblong and of a cylindric figure; the Style is ca- pillary and turns upwards, and the ftigma is hairy and placed forward at the apex of the ftyle* The fruit is a large and long pod of a conipreffed figure and Somewhat gibbous; it contains a few kidney fhaped feeds. Linncei Gen. PI. p. 349. Town. Lift. p. 417. Rivin. 4. 74.

ROCELLA, a kind of fucus or fea wrack found in the Mediterranean and other feas, and in fome places ufed by the dyers for a purple colour, and called by the botanical writers, in general, alga tintloria. Cafp. Bauhin. Pin. p. 365.

ROCHET, the name given to a fifh, otherwife called cuculus and red gurnard. See Cuculus and Gurnard.

ROCHETTA, in the glafs trade, another name for polverine. Seethe article Polverine.

ROCKS {Cycl.) — Thefe are generally fuppofed great enemies to vegetation, and the people of Scotland have been deterred from cultivating many of their heft lands, from an obser- vation that they had*a rockyhottom. This is however but a vulgar error among them, fat rocks of a proper kind and properly difpofed, as very many of theirs are, fertilize and are beneficial to the land, not hurtful.

In many parts of England we fee gardens the moft beau- tiful that can be imagined, both in regard to flowers and excellent plants, on a foil where the burtom is a hard rock, and the earthy covering not more than a foot or thereabout in depth. In fome of thefe, all the disadvantages the Scotch complain of take place, and yet the gardens are fruitful, many of them having lofty hills on the fouth fide; the declivity due north, and the rock perfectly bare next the walls on the north fide.

The north fides of thefe hills in this very afpect, only with the rock covered with two or three foot of earth make very good hop gardens, producing a vaft quantity of a very valuable commodity at a final] expence j and it is remarkable that thofe gardens, which ftand in this expofure, inftcad of being fubject to particular evils, often efcape thofe blafls and other mifchiefs which affect the plantations of the fame kind on the fouth fide of the hills. It might be a very valuable article of trade, if the bleak hills of Scotland, or thofe of Some of our northern plantations in America, could be made thus fruitful in fo ufeful a commodity, and there feems only the want of a proper trial.

Another extremely valuable plant that might be railed on thefe barren rocky places, as they are generally fuppofed to be, is flax, in places where the defcent tstoofteep fur plough- ing in the common way. It has been proved that a hand plough with a item of afh of about Seven feet long, and a plate on each fide near the end to turn the turf, a coulter to be let out fhorter or longer to four or five inches deep to cut the earth up as deep as it lies upon the rock,- and an iron wheel, may be managed with cafe and convenience by two people, and will prepare ground for producing large crops of the fincft flax. The belt Sort of flax Seed of Flanders Sown on this fort of ground Succeeds fo well, that if brought

into