in botany: A genus of plants belonging to the class of syngenesia, and to the order of polygamia necifaria; and in the natural system arranged under the 49th order, composite. The receptacle is paeleanous; the pappus has a two-horned margin, and the calyx is squarrose. There are eight species; the laciniatum, teretibinthinum, perfoliatum, connatum, aftericum, trifoliatum, foliagoides, and trilobatum. The first six of these are natives of North America. Silver, one of the perfect metals, and the whitest and most brilliant among them all, is of the specific gravity, according to Bergman, of 10.552; but according to Kirwan, of 11.095. Its ductility is not greatly inferior to that of gold, as a grain of silver leaf measures somewhat more than 51 square inches; and the silver wire used for astronomical purposes measures only the 750th part of an inch in diameter; which is no more than half the thickness of the hair of the human head. It is harder and more elastic than lead, tin, or gold; but yields to than copper, platinum, or iron: like other metals it grows hard by hammering, but is easily reduced to its former state by annealing. It is more ductile than gold, and is particularly acted upon by sulphurous vapours; hence its surface tarnishes in the air, and assumes a dark brown colour.

"It has been long thought (says Mr. Fourcroy) that silver is indestructible by the combined action of heat and air. It is certain, that this metal kept in fusion, without contact of air, does not appear to be sensibly altered; yet Junker had affirmed, that by treating it a long time in the reverberatory furnace, in the manner of Isaac Hollandus, silver was changed into a vitreous calx. This experiment has been confirmed by Macquer. That learned chemist exposed silver 20 times successively in a porcelain crucible to the fire of the furnace at Seves; and at the 20th fusion he obtained a vitrified matter of an olive green, which appeared to be a true glas of silver. This metal, when heated in the focus of a burning glass, has always exhibited a white pulverulent matter on its surface, and a greenish vitreous covering on the support it rested upon. These two facts remove all doubt respecting the alteration of silver; though it is much more difficult to calcine than other metallic matters, yet it is capable of being converted after a long time into a white calx, which, treated in a violent fire, affords an olive-coloured glass. It may be possible perhaps to obtain a calx of silver by heating this metal when reduced into very fine laminae, or into leaves, for a very long time in a matrix, as is done with mercury."

Macellan informs us, that by melting in a due proportion with gold or steel, silver becomes greenish or bluish; so that it is capable of producing the white, yellow, red, green, blue, and olive colours, more or less conspicuously according to the various circumstances of heat and proportions of the mixture. Though he makes mention of the vitrifications by Macquer already taken notice of, he denies that it can be calcined by heat alone. "Silver (says he) is so fixed by itself in the fire, that, after being kept a whole month in fusion, it had only lost one 60th part of its weight, which might be on account of some alloy. It is therefore incapable of being calcined by mere heat; and the calx of silver, which can only be made by means of its solution in acids, is reducible to its metallic form without the addition of any oxigenous substance. But when silver is exposed to the violent heat of the solar rays collected by a powerful lens, a kind of smoke is seen surrounding it, which proves at last to be the minute particles of the metal raised and dispersed by heat, as is evident if a thin plate of gold be exposed to it; for then the particles of silver are seen upon the gold in the same manner as those of gold are seen upon silver in a similar experiment."

By slow cooling after it has been melted, silver crystallizes into quadrangular pyramids. M. Baume observes, that, in cooling, it assumes a symmetrical form, observable on the surface by small fibres resembling the feathers of a pen. M. Fourcroy observes, that the fine button obtained by cupellation, often presents on its surface five or six sides arranged amongst each other like a pavement; but the crystallization in tetrahedral pyramids has not been observed particularly excepting by Messrs. Tillet and Mongez. It has been supposed that silver melts with a smaller degree of heat than copper; but the late improved thermometer of Mr. Wedgwood shows that this is a mistake; silver requiring 130° of Fahrenheit more than copper to bring it into fusion. It is found in the earth,

1. Native, generally of the fineness of 16 carats; and of this there are several varieties. 1. Thin plated or leaved. 2. Capillary silver, of fine or coarse fibres or arborecent, from Potosi in America and Kunberg in Norway. 3. A kind is also met with resembling coarse linen in the surface, which in Saxony is called knit cobalt. Abundance of this kind is to be met with in Potosi, but more rarely in Saxony and Norway. 4. Sometimes native silver is met with in a crystalline or regularly figured state with shining surfaces. This is found at Kunberg, but is very scarce. There appears likewise a kind of crystallization on the thin plates of native silver, their surfaces being full of minute pyramidal crystals. Most of the American silver is of the native kind; so is that at Kunberg in Norway. It is not, however, met with native to commonly in other European mines. A very small quantity of it is found in the mines of Salberg in Westphalia, and of Lofoten in Dalarne, and several other places in Sweden. It has been found in pretty large lumps in clay mixed with nickel, partly decayed or withered; in which situation it formed the compound called the fercus antiferum, or goose dung ore. 5. A piece of native silver in coal is shown in the mineralogical academy at Freyberg; and Laidman, quoted by Le Camus, speaks also of a similar silver ore found in a mine of pit-coal. The capillary silver, according to the observations of Henckel and Rome de Lille, seems to have been produced by a decomposition of red silver ore; and Wallerius affirms, that if sulphur is mixed in a gentle heat with silver, the latter takes a capillary form. 6. Native silver is likewise sometimes found in the form of spider's webs, and for that reason called by the Spaniards aranea. 7. It is met with in branches formed by octaedrons inserted into one another. Some of these show the mark of a leaf of fern or of a tree; others are cubes or single octaedrons, whose angles are truncated, though these last are but rare. 8. It is often found dispersed through sand and ochre, as well as in grey limestone in Lower Austria, and in a greenish clay near Schenitz, or mixed with ochre, clay, and calciform nickel. It is generally alloyed with copper, sometimes with gold, iron, or regulus of antimony; and sometimes it contains even five per cent. of arsenic. That found near Kunberg contains so much gold, that the colour of it is yellow.

Wallerius distinguishes seven species of native silver; viz. 1. In irregular masses and lumps, at Kunberg in Norway and other places, in a bed of clay. 2. In a granular and jagged form in America and Norway. 3. Arborecent, in the places already mentioned. 4. In thin thin leaves, between the fissures of stones, in Norway and Germany. In a capillary form, in the places already mentioned, including the cobweb silver of the Spaniards already mentioned. 6. Crystalized. 7. Superficial. Mr Daubenton enumerates eight varieties of native white silver, of different forms, most of which have been already enumerated. The materials in which this metal is most commonly found in its native state are, baro-felenite, limonite, felenite, quartz, chert, flint, serpentine, gneiss, agate, mica, calcareous spar, pyrites, schilus, clay, &c. Sometimes it is met with in large masses, of the weight of 60 pounds or more, in or near the veins of most metallic ores, particularly in Peru and in various parts of Europe, of a white, brown, or yellowish colour. In Norway and at Alsace it is found in the form of solitary cubes and octahedral lumps, of 50 and 60 pounds weight.

2. Native silver alloyed with other metals. 1. With gold, as in Norway, where it contains so much as to appear of a yellow colour. 2. With copper. 3. With gold and copper. 4. Amalgamated with mercury, as in the mines of Salberg. M. Rome de Lille mentions a native amalgam of silver and mercury found at Michel Landberg in the duchy of Deux Ponts, in a ferruginous matrix, mixed with cinabar, and crystallized in a hexagonal form, and of a large size. It was before the French revolution preserved in the king's cabinet at Paris. 5. With iron. According to Bergman, this ore contains two per cent. of iron; but Mongez informs us, that it often does not exceed one per cent. 6. With lead. "Silver (says Mr Magellan) is always contained in lead, though the quantity is generally insufficient to defray the expense of separating it. In the reign of Edward I. of England, however, near 1600 pounds weight of silver were obtained, in the course of three years, from a lead mine in Devonshire, which had been discovered about the year 900. The lead mines in Cardiganshire have at different periods afforded great quantities of silver; so that Sir Hugh Middleton is said to have cleared from them £2000 in a month. The same mines in the year 1745 yielded 80 ounces of silver out of every ton of lead. The lead in only one of the smelting houses at Holywell in Flintshire produced no less than 37521 ounces, or 3126½ pounds of silver from the year 1754 to 1756, and from 1774 to 1776. There are some lead ores in England, which, though very poor in that metal, contain between 300 and 400 ounces of silver in a ton of lead; and it is commonly observed, that the poorest lead ores are the richest in silver; so that a large quantity of silver is probably thrown away in England by not having the poorest sort of lead ores properly assayed." 7. Mr Monnet found silver united with arsenic among the ores which came from Guadalcanal canal in Spain, and an ore of the same kind is furnished by the Samson mine near Andreaberg in the Hartz; but Mr Mongez very properly remarks, that these ores must be distinguished from such as have the arsenic in the form of an acid; for in this case they are properly mineralized by it, whilst there can only be a mixture of native silver, or some of its calces with arsenic in its reguline form. 8. Bergman mentions silver in a state of union with antimony. The ore yields some smoke when roasted, but has not the garlic smell observable in the arsenical ores. 9. The white silver ore, found in the mines near Freyberg, has the metal united to the regulus of arsenic and iron, the three metallic ingredients being nearly in equal proportions. All the extraneous matters with which the silver is united are sometimes in exceedingly small proportion, but not to be neglected where they exceed the hundredth part of the whole mass. 10. A particular kind of stony silver ores is mentioned by Wallerius under the title of lapideae, and which contain the following varieties, viz., the calcareous silver ore at Annaberg in Austria, when the metal is mixed with an alkaline limestone; the spathoic ore, either white, variegated, or yellowish, found at Schenitz in Hungary; the quartzite white ore in a powdery form, mixed with ferruginous scoria, found at Potosi in America; the dark and variegated quartz-ore silver ores, with many other subdivisions distinguished from one another by little else than their colour.

Silver is found mineralized by various substances; as,

1. With sulphur in the glassy or vitreous silver ore; though this name seems rather to belong to the minera argentii cornea or horn silver ore, to be afterwards taken notice of more particularly. It is ductile, and of the same colour with lead, but quickly becomes very black by exposure to the air; though sometimes it is grey or black even when first broken. It is found either in large lumps, or inhering in quartz, gypsum, gneiss, pyrites, &c. Its specific gravity, according to Kirwan, is 7,200. An hundred parts of it contain from 72 to 77 of silver, and it is rarely contaminated with any other metal.

Professor Brunnich says that it contains 180 merks of silver in the hundred weight. The medium between the glas ore and the red gilder ore is called rohglaswechsel in Hungary, and brittle glas ore in Saxony. It is black, and affords a powder of the same colour when pounded. In the mines of Himelflirst near Freyberg, it is said to have held 140 merks, but these pieces are very scarce at present; and indeed the Hungarian glas ores in general are now very scarce, as Professor Brunnich informs us, though they are now and then found in the windshafts, which are frequently covered with a thin membrane or rather crust, of the colour of pyrites. Mr Magellan says that this ore is nothing else but native silver penetrated by sulphur; for, on being exposed to a slow heat, the latter flies off, and the silver shoots into filaments. There are nine varieties of it. 1. Like black lead, or plumbago, the most common kind of any. 2. Bruckman mentions a kind brown on the outside and greenish within. 3. The yellow ore has its colour from some arsenic contained in it, which forms an ornament with the sulphur. 4. It is also found of a greenish, and 5. bluish colour; the latter is friable, like the scoria of metals, and is called at Freyberg Schlackenerz, or the ore of scoria. 6. It is found also in the arborecent. 7. Lamellated. 8. Crystalized into octahedral or hexagonal prisms, and into ten pyramids with ten sides. 9. Lastly, it is found superficially covering the stones or masses of other ores.

2. The pyrites argenteus of Henckel contains silver Cronfeldt, and iron mineralized with arsenic. There are three varieties of it. 1. Hard, white, and shining ore, of a compact, lamellar, or fibrous texture. The brightest kind has least silver, only giving 6 or 8 ounces per quintal, and the richest about ten per cent. It is found in Germany and Spain. It contains no sulphur. 2. Of a yellowish white colour, and striated texture resembling bismuth, but much harder. It is found in Spain, and yields about 60 per cent. of silver. 3. In another kind the quantity of arsenic is so great, that it would scarcely deserve the name of silver ore if the arsenic were not very easily diffused. It is soft and easily cut; has a brilliant metallic appearance, and consists of conchoidal laminae. A quintal contains only from four to six ounces of silver, but it is easily reduced by evaporating the arsenic, after which the silver is left behind slightly contaminated with iron.

3. The red or ruby silver ore, the rothzulden of the Germans, has the metal combined with sulphur and arsenic. It is a heavy shining substance, sometimes transparent, and sometimes opaque; the colour generally crimson, though sometimes grey or blackish. It is found in shapeless masses, or crystallized in pyramids or polygons, sometimes dendritic or plated, or with radiated incrustations. It is found in quartz, flint, spar, pyrites, sparry iron ore, lead ore, cobalt ore, jasper, baro-felinite, gneiss, &c. When radiated or flatted, it is called rothzulden blatt. It cracks in the fire, and detonates with nitre. Its specific gravity is from 5,400 to 5,684. Bergman informs us, that this kind contains, in the hundred, 60, sometimes 70, pounds of silver, 27 of arsenic, and 13 of sulphur. The darkest coloured ores are the richest, the yellow kinds much poorer; but the most yellow do not belong to this species, being in fact an orpiment with 6 or 7 per cent. of silver. This last kind is brought chiefly from Potosi in America, and is called rosi-pler by the Spaniards.

4. The schwartz gulden, or silver malm, contains the metal mineralized by sulphur and a small quantity of arsenic and iron. It is of a black footy colour, and was supposed by Cronstedt to contain a good quantity of copper, to which its colour was owing; but later experiments have evinced, that there is no copper at all in it. It is either of a solid or brittle consistence, and of a glaify appearance when broken, or of a looser texture, and footy or deep black colour; or it is found like moss, or thin leaves, lying on the surface of other silver ores, or those of lead and cobalt, or in clays, ponderous spar, gneiss, &c. It contains from 25 to 60 per cent. of silver.

5. The minera argentii alba, the Weißgulden ore of the Germans, is a heavy, soft, opaque substance, fine grained or scaly, bright and shining in its fractures, of a whitish, steely, or lead colour; sometimes crystallized in pyramidal or cylindrical forms, but often in amorphous grains, or resembling moss, or in the form of thin laminae incrustating other bodies, found in quartz, spar, stellitein, pyrites, blend-ore, cobalt-ore, sparry iron ore, fluors, &c. It is very fusible. Its specific gravity is from 5 to 5,300. Its proportion of silver from 10 to 30 per cent. It is found, though not commonly, in Saxony, Hungary, the Hartz, and St Marie aux Mines.

6. The weifertz, or white silver ore, is an arsenical pyrites, containing silver. It is met with in the Saxon mines so exactly resembling the common arsenical pyrites, that it cannot be distinguished from it by inspection. Cronstedt supposes that the silver it contains may exist in a capillary form; but Professor Brunnich thinks this is not altogether the case. It is very scarce, but met with near Freyberg. There is likewise a brown acuin having the appearance of rags, met with in the crevices and upon the lumps of cubic lead ore in a mine near Clausthal and other places, which contains a great quantity of silver. It is of a whitish shining colour; hard, granulated, and solid, sometimes striking fire with steel. It discovers a mixture of arsenic, by emitting a garlic smell when heated.

7. The leberertz of the Germans has the metal combined with sulphurated antimony. It is of a dark grey and somewhat brownish colour. A variety of a blackish blue colour is found in the form of capillary crystals, and called federertz or plumose silver ore. It is met with in Saxony, and contains sometimes a mark or half a pound, sometimes only two, three, or four ounces, and sometimes only a mere trifle of silver, per cent. There is another silver ore, also called leberertz by the Germans, which contains arsenic and regulus of antimony. This ore is sometimes also found of a dark grey colour; for the most part amorphous, but sometimes crystallized into pyramids. It appears red when scraped, and contains from one to five per cent. of silver. The greatest part of this ore is copper, and the next arsenic. According to Bergman, the copper amounts to 24 per cent. It is found in Transylvania; and a kind was lately discovered in Spain, of a hard solid consistence, and of a greyish blue colour.

8. The goede ding ores contain silver mineralized with sulphur in combination with iron, arsenic, and cobalt. It looks like the weifzulden, excepting that the cobalt, by its decomposition, gives it a rosy appearance. There are two varieties; one of a dull tarnished surface and ferruginous look; the other has a shining appearance like the leberertz. It contains from 10 to 40 or 50 per cent. of silver. The arsenic is in an acid state, and united to the cobalt.

9. The dal fahleretz contains silver mineralized with sulphurated copper and antimony, and resembles the dark-coloured weifzulden, giving a red powder when rubbed. It is found either solid or crystallized, and is met with in the province of Dal, where it is melted by a very difficult process, calculated to preserve the different metals it contains. There is another kind which has arsenic united to the rest of the ingredients. It is only the grey copper ore impregnated with silver, of which it contains from one to twelve per cent. the quantity of copper being from 12 to 24 per cent. and the remainder consisting either of sulphur or arsenic, with a little iron. It is the most common of all silver ores; and M. Monnet remarks, that where copper is united to arsenic, silver is always to be found. A variety has been found at Schemnitz, containing a portion of gold also.

10. The pecheblende is an ore of zinc containing silver, and is met with in the Saxon and Hungarian mines among the rich gold and silver ores. It is either of a metallic changeable colour or black. Of these there were formerly two varieties, viz. either in the form of fine scales or in balls, but the latter is now entirely unknown. A black blend is found in Bohemia, which is very heavy, with the surface somewhat elevated like some kinds of haematites, but no silver has yet been extracted from it.

11. The bleeglanz, potters ore, or galena, contains silver mineralized with sulphurated lead. It is also called pyritous silver, and is of a brown colour, yielding but a very small portion of metal. It is met with at Kunftberg. When the silver is combined with sulphurated lead and antimony, the ore is called *friperz*.

12. The *marcasite* containing silver has the metal united with sulphurated iron. There are great varieties of this ore holding different proportions of the metal; some produce only half an ounce of silver per cent. A liver-coloured marcasite is found at Kunberg in Norway, containing from three to three ounces and a half of silver per cent.

13. Silver is found mineralized with sulphurated and arsenical cobalt; the stone sometimes containing dendrites. These kinds keep well in water, but generally decay in the air, and lose the silver they contain. It is found at Morgentern near Freyberg and Annaberg.

14. The *buttermilk* ore contains silver mineralized by sulphur, with regulus of antimony and barytes. It is found in the form of thin particles or granular spar. Wallerius says that it is soft like mud, and feels like butter. He suspects it to be produced from other silver ores washed away by running waters. Bomare adds, that the miners look upon it as a certain sign of other ores in the neighbourhood, though some are persuaded that it is only an unripened silver ore, which would soon become perfect.

15. The *combustible* silver ore is a black brittle substance, leaving about six per cent. of silver in its ashes. It is in fact a perfect coal in which silver is found.

16. The *hornetze*, or horn silver ore, in which the silver is united with the muriatic acid, is the rarest of all the silver ores. It is sometimes found in snowy cubic crystals, but is met with of many different colours. Its principal characteristic is to change to a violaceous brownish colour when exposed to the sunbeams, as happens also to the artificial luna cornea. It is frequently crystallized in a cubic form, though not always of a white colour. Sometimes it resembles an earth easily fusible without smoke. There is a black kind, friable, and easily reducible to powder; the other is in some degree malleable, may be cut with a knife, and takes a sort of polish when rubbed. The vitreous silver ore, which is sometimes mixed with the horn silver, is soluble in nitrous acid; and this affords a method of separating them, the horn silver ore being insoluble in that menstruum. When the horn silver is free from iron, it generally contains 70 per cent. of silver at least; but these ores mostly contain some portion of iron, a small part of which is even united to the marine acid. This kind of ore was first analyzed by Mr Woulfe, who discovered the presence of the vitriolic acid in it.

17. Another kind of horn silver ore is mentioned by Mr Bergman, in which the metal is mineralized by the vitriolic and marine acids, along with some sulphur. He doubts, however, whether the mineralization be perfect in this case, as the salt and sulphur do not admit of any other than a mechanical union. But since iron is often found in these ores, a marcasite may thus be sometimes formed.

18. The *silver goose dung ore* is of a greenish colour, with a mixture of yellow and red. Some think it is a mixture of red silver ore and calx of nickel.

19. The *foliaceous* silver ore. The colour of this ore is mortdoré. Some imagine it to be a native silver ore; others that it is a mixture of galena, ochre, and silver. It is sometimes found in the mountain cork, and is so light that it will swim upon water. It contains but one ounce of silver per quintal.

These are all the varieties hitherto observed in which silver is met with in the earth, though it may perhaps occur in various other forms. It would be worth while to examine whether, in those countries where gold and silver are found in large quantities, the precious metals may not be contained in some proportion in the most common ores, more especially when the particles of gold and silver have not been able to extricate themselves in such a manner as to lie separate in fissures, veins, or hollow places of the mine. A mineralization of silver with alkali is said to have been lately met with at Annaberg in Austria; but the account of it as yet can scarcely be depended upon. Professor Brunnich says, that the silver contained in the limestone at that place appears to be native when the stone is polished.

The purest silver is that which is extracted from luna cornea, and is the only kind that ought to be trusted in the nice operations of chemistry. The process, however, is very tedious, and presents a very unexpected phenomenon, as this metal, though one of the most fixed, is nevertheless volatilized in the operation in such a manner that it exhales through the pores of the crucible; and small globules of silver are afterwards found in the cover, and even in the support of the crucible. According to Cramer, this loss may be prevented by fumigating the crucible with black soap, and mixing with the luna cornea half its weight of oil or tallow, which last must also be added by little and little during the operation.

M. Magellan takes notice of a remarkable appearance observable in dissolving silver in the nitrous acid. He observes, that this acid is its specific menstruum, attacking it even when cold with considerable effervescence, growing hot, and emitting a considerable quantity of orange-coloured fumes, which diminish in proportion as the saturation advances. The metal appears of a pale brown colour in the conflict, and the solution becomes quite black. This last appearance, however, is owing to a thin, black, fuliginous substance, like smut, which is at once formed into a crust on the surface of the thin plates of silver in the first attack of the acid upon them. This is a very singular phenomenon, and hitherto unaccounted for, these black crusts being comminuted into smaller and smaller particles by the action of the acid; and, when the effervescence is over, they are seen distinctly to fall to the bottom of the vessel, and to form a black sediment, leaving the liquid solution quite transparent, but of a blue colour inclining to green. This colour might be attributed to some small mixture of copper, though the silver used in the experiment was of the purer kind. The chemists of Dijon say, that the nitrous solution of silver looks of a fine blue colour, if the acid be pure and well concentrated; but if it has any mixture of vitriolic or marine, a precipitation of vitriolated silver or luna cornea takes place. Afterwards the solution becomes as colourless as water, but gives a lasting black tinge to animal substances. This solution is of great use in chemistry, serving to form the lunar caustic, to purify the common aquafortis from a mixture of the vitriolic and marine acids, and is a very nice test of the existence of these acids in mineral waters.

Silver does not combine with earths, even by the most violent heat, though Mr Fourcroy supposes that its calx might Silver might give an olive green to glass. Mr Magellan informs us, that its calx, precipitated by volatile alkali, gives a yellow colour to glass, and that he has seen it retained in this manner so high as almost to appear of a red colour. It unites with most metals, even with iron. The nature of this alloy has been but little inquired into, though Fourcroy is of opinion that it may probably be of the greatest utility in the arts. It combines in all proportions with copper, by which it is not deprived of its ductility, but renders it harder and more sonorous; by which means it is often used in bells. It is otherwise highly useful, on account of its indestructibility by fire and air, and its extreme ductility. Its fine colour renders it extremely proper for ornamental purposes, and it is applied like gold on the surface of different bodies, and even on copper. It likewise enters the texture of rich silks; but its most considerable use is that of being employed as money of an inferior value to gold. In this case, it is alloyed with one-twelfth part of copper. It is likewise often employed in making household utensils of all kinds, though its great price renders it less common than it would otherwise be for this purpose. For plate, it is usually alloyed with one twenty-fourth of copper, which gives it a greater degree of hardness and coherence, without rendering it in the least noxious.

Silver has also been used in medicine; but its extreme causticity, when dissolved in the nitrous acid, and its inactivity otherwise, have brought it into disuse. The crystals of silver have been recommended in very small quantity in tropical cases; but they are by no means superior, or even equal in efficacy, to much safer medicines. The solution of silver, under the name of Greek water, has been used for the purpose of dying hair of a dark colour; and the same solution evaporated to a consistence, and fused, forms the lunar caustic of the thaps.

Shell Silver, is prepared of the shreds of silver leaf, or of the leaves themselves, for the use of painters, after the same manner as shell gold. See Shell-Gold.