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attributes similar power to certain fishes of the Nile, which the head is also protected by bony plates; the mouth is buit he called choerus (xoipos), and which are supposed by some slightly cleft, and provided with four long barbules; the naturalists to belong io the modern genus Synodoniis. second dorsal has a bony spine in front; the foremost ray

The genus Doras is divided into two sections on account of the pectoral fins is strong, but that of the anterior dorsal of the structure of the mouth. In some it is situated at the is comparatively feeble and short. The species of Callichthys end of a depressed muzzle, and is provided with two broad appear to be confined to the tropical portions of South bands of delicate teeth, both in the upper and lower jaws. America. [CALLICHTHYS.) In others the opening of the mouth is situated on the under Genus Arges, Cuv. and Val.- The principal characters of side of a conical muzzle, and the opening is of a circular this genus are—teeth bifid at the extremity, and with the form-here the teeth are either wanting or are hardly points curved inwards; palate destitute of teeth; opening of visible; the maxillary barbules are sometimes furnished ihe mouth large; maxillary barbules two in number ; anwith small lateral branches. To the first of these sections terior dorsal fin small, and with the front ray feeble ; adipose belongs the Silurus costatus of Linnæns, a species found in fin long; the other fins with the outer rays prolonged into the rivers of Guiana.

a filament. A species of Doras, described by Dr. Hancock, in the The species which forms the type of this genus (Arges fourth volume of the Zoological Journul, p. 241, under the sabalo, Cuv. and Val.) is a small fish about eight incles in name of D. costatus, is a native of Demerara, where it is length, which was brought by Mr. Pentlaur from Upper called the Flat-head Hassar: it possesses the singular property, Peru, being found in the reighbourhood of the mission of says Dr. Hancock, of deserting the water, and travelling Santa Anna, at a height of from 4500 to 4800 French over land. 'In these terrestrial excursions large droves of metres above the level of the sea. The specimen was given the species are frequently met with during very dry seasons, to M. Valenciennes, who prized it much, since it threw a for it is only at such periods that they are compelled to this light on the affinities of a fish described by Humboldt, under dangerous march, which exposes thiem as a prey to many the name Pimelodus Cyclopum, relating to which that and such various enemies. When the water is leaving the author lias given such an interesting account. The Pimepool in which they commonly reside, the Varrows (a species lodus Cyclopum, which M. Valenciennes thinks most proof Esox, Linn.), as well as the second species of Hassar, to bably belongs to the present genus, is about four inches in which I shall presently refer, bury themselves in the mud, length, and is found in lakes at the height of 3500 metres while all the other fishes perish for want of their

natural above the level of the sea. But the most remarkable cirelement, or are picked up by rapacious birds, &c. The flat- cumstance relating to these fishes is that they are frehead Hassars, on the contrary, simultaneously quit the quently ejected in the eruptions from the volcanoes of the place, and march over land in scarch of water, travelling for kingdom of Quito, and in such quantities that the fetid a whole night, as is asserted by the Indians, in search of odour arising from their putrefaction was perceired at a their object. I have ascertained by trial that they will live great distance, and the putrid fevers which prevailed in many hours out of water, even when exposed to the sun's those districts were attributed to the niasmaia they prorays. Their motion over land is described to be somewhat duce. These fishes sometimes issued from the crater of the like that of the two-footed lizard. They project themselves volcano, and sometimes from lateral clefts, but constantly at forwards on their bony arms by the elastic spring of the tail an elevation of from 5000 to 5200 metres above the level of exerted sideways. Their progress is nearly as fast as a man

In a few hours millions are seen to descend from will leisurely walk. The strong scuta or bands which en- Cotopaxi, with great masses of cold and fresh water. velope their body must greatly facilitate their march, in the The

genus

Brontes, Cuv. and Val., is founded upon a fish manner of the plates under the belly in serpents, which are possessing all the characters of the preceding genus (and raised and depressed by a voluntary power, in some mea- which, it appears, like the Pimelodus, is thrown out from sure performing the office of feet. It is said that the other the volcanoes of Cotopaxi), but which differs in having no species, the round head (Callichthys littoralis, Hancock), adipose fin. has not been known to attempt such excursions, although Genus Astroblepus, Cuv. and Val., consists of but one it is capable of living a long time out of its element; but, as species (the Astroblepus Grixalvii of Humboldt). This I before observed, it buries itself in the mud in the manner fish possesses all the characters of the genus Bronles, bavof the Yarrows, when the water is drying up.

ing, like it, the head depressed, the eyes directed upwards, • The Indians say these fishes, carry water within them a single dorsal fin, the external rays of the fins prolonged for a supply on their journey. There appears to be some into a filament, and four branchiostegous rays, but it postruth in this statemeni; for I have observed that the bodies sesses no ventral fins. This fish is found at Rio de Palace, of the Hassars do not get dry, like those of other fishes, when near Papayana, where it is known by the name pescado taken out of the water; and if the moisture be absorbed, or negro; it attains about fifteen inches in length. they are wiped dry with a cloth, they have such a power of se Genus Heterobranchus, Geoff.- Here the head is furcretion that they become instantly moist again. Indeed it nished with a rough bony shield, which is flat and broader is scarcely possible to dry the surface while the fish is than in the other Silurians, on account of the lateral laminæ living.'

furnished by the frontals and parietals, which cover the Both the species of Hassar here mentioned, it appears, orbital and temporal bones. The operculum is still smaller make nests in which they lay their eggs in a flattened cluster, than in the preceding fishes, and what chiefly distinguishes and cover them over most carefully. This care does not end these fishes from others of ihe family is, that, besides the here. They remain by the side of the nest till the spawn is ordinary branchiæ, they have an apparatus ramifying like hatched, with as much solicitude as a hen guards her eggs; the branches of a tree adhering to the upper branch of the both the male and female Hussar, for they are monogamous, third and fourth branchial rays; the branchiostegous rays steadily watching the spawn, and courageously attacking vary from eight or nine to fourteen or fifteen in number. any assailant. Hence the negroes frequenily take them by The pectoral spine is strong and denticulated, but there is putting their hands into the water close to the nest; on no bony spine io the dorsal fin. The body is elongated and agitating which, the male Hassar springs furiously at them, naked, and the dorsal and anal fins are greatly extended and is thus captured.

the longitudinal direction. The barbules are eight in num• The round-head forms its nest of grass; the flat-head, of ber. The species inhabit the rivers of Africa, and some leaves; both at certain seasons burrow in the bank; they of those of Asia. lay their eggs only in wet weather. I have been surprised In some species the long dorsal fin is supported throughto observe the sudden appearance of numerous nests in a out by rays; these constitute the subgenus Clarias, Val.; morning after rain occurs, the spot being indicated by a and in others there is a dorsal fin supported by rays, and a bunch of froth, which appears on the surface of the water second behind this, which is adipose. To them the term over the nest; below this are the eggs, placed on a bunch of Heterobranchus is restricted in the Histoire Naturelle des fallen leaves or grass, if it be the littoral species, which they Puissons. cut and collect together. By what means this is effected Genus Saccobranchus, Cuv. and Val.—This genus is seems rather mysterious, as the species are destitute of cut founded upon the Silurus Singio of Hamilton's Fishes of the ting teeth. It may possibly be by the use of their serrated Ganges,' which possesses some interesting peculiarities in its arms, which form the first ray of ihe pectoral fins.'

internal organization, pointed out by Mr. Wyllie, in the 'ProGenus Callichthys, Linn.—The species of this genus ceelings of the Zoological Society, for May, 1840. have the body almost entirely covered by large bony plates, Genus Plotosus, Lacépède, is distinguished by the elon. thesc forming four longitudinal ranges, iwo on each side: gated form of the body and the possession of two dorsal lins, P. C., No. 1361.

Vol. XXII.--D

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the hindermost being supported by rays as well as the other. I then holding his court, who received him with every mark The head is protected by a bony plate, the lips are fleshy of distinction, but would not hear his message until he had and pendent, the jaws are furnished with strong and conical himself returned to Ispahán, where he directed Silva to teeth, and the vomer with rounded teeth. The species in- wait till his arrival. Accordingly, after a stay of two habit India.

months at Kazwín, the Spanish envoy returned to IspaGenus Aspredo, Linn.—The fishes of this genus, says hán, where Shah Abbás arrived shortly after, in July, Cuvier, present very singular characters, particularly in the 1619. He granted Silva an audience; but though he maflattening of the head and in the dilatation of the anterior nifested a wish to conclude a commercial treaty, and to be portion of the trunk, which chietly arises from that of the upon friendly terms with Spain, the Shah refused to subbones of the shoulder; in the proportionate length of the scribe to two conditions stipulated by the ambassador of tail; in the small size of their eyes, which are placed in the Philip III., namely, that he should restore some fortresses upper surface of the head. The intermaxillaries are situated belonging to Ormuz, which he had lately seized; and that under the ethmoid, directed backwards, and are only fur- he should exclude all other European nations from trading nished with teeth in their hinder margin. But the most with his dominions. The negotiations for the treaty being striking character consists in there being no power of motion thus suspended, Silva left Ispahan on the 25th of August, in the operculum, a character which distinguishes the pre- 1619, and returned by the same route to Goa, where he sent genus from all other osseous fishes. The branchial | landed in November, 1620. From Goa he sailed to Spain, opening consists of a simple slit in the skin under the ex where he died in 1628. ternal edge of the head, and the branchiostegous membrane During his residence in Persia Silva wrote an itinerary of is provided with five rays; the dorsal fin is of moderate size; his travels, with an account of such events as came within the anal is long; the tail moderate, and the adipose fin is his observation; and a sketch of the manners and customs wanting: the whole of the body is smooth and without bony of the inhabitants of that empire. This work was never plates. The species are found in the tropical parts of South printed in the original Spanish, though a French translation America.

appeared in 1667, under the title of L'Ambassade de Don Genus Chaca, Cuv. and Val., which is the next in succes Garcias de Silva Figueroa en Perse, contenant la Politique sion in the Histoire des Poissons, is founded upon the Pla- de ce Grand Empire, les Meurs du Roi Shah Abbas, et une tystacus Chaca of Buchanan Hamilton. It inhabits the relation exacte de tous les Lieux de la Perse et des Indes où rivers of India.

cet Ambassadeur a été l'espace de huit anneés qu'il y a deThe genus Sisor is also founded upon a single species meuré,' par M. Wicq fort, Paris, 1667, 410. It is one of the described (under the name Sisor rhabdophorus) by the best accounts of Persia that we possess, and is much comauthor just mentioned, in his Fishes of the Ganges. mended by Chardin. During his residence in Goa Silva Genus

Loricaria.-Linnæus gave this name to a group also made an abridgment of Spanish history, which appeared of Siluridæ distinguished by the head and body being co at Lisbon soon after his death : Breviarium Historia vered throughout by large angular bony plates ; they differ Hispanicæ, Lisbon, 1628, 4to. A Latin letter of his, dated moreover from certain other Siluri which have the body Ispahan, 1619, and addressed to the Marquis of Bedmar, in protected by plates (such as Cullichthys and Doras), in having which he gave a short account of his travels, was also pubthe opening of the mouth on the under side of the muzzle, lished at Antwerp: Garciæ Silva Figueroa, Philippi III. in this respect approaching the genus Synodontis. The Hispaniarum Indiarumque Regis, ad Persarum Regem Leintermaxillaries are small and suspended beneath the gati, de Rebus Persarum Epistola,' Antw., 1620, 8vo, muzzle, and the mandibles are transverse and not united; SILVER, a metal whicb has been well known and highly they are furnished with long and slender teeth, and these valued from the remotest period-circumstances which are are flexible and terminate in a hook. The mouth is en readily explained by the facts of its occurring frequently circled by a large, circular, membranous veil; the pha- native, and possessing great lustre and fitness for immediate ryngeal bones are furnished with numerous teeth rounded use without being subjected to any metallurgic process. like paving-stones. The true opercula are fixed as in Aspredo, but two small external plates, which are movable,

Ores of Silver. appear to take their place. The branchiostegous rays are Native Silver.-This occurs crystallized, arborescent, or four in number. The first ray of the dorsal, pectoral, and dendritic, capillary, reticulated, granular, and massive. The anal fins is in the form of a strong spine.

primary form of the crystal is a cube. It has no cleavage This genus is subdivided into two subgenera. In the Fracture hackly. Colour white, but externally often one (Hypostomus, Lacép.), there are two dorsal fins; the blackish, owing probably to the presence of a little sulphur. hinder one is small and provided with but one ray. The Hardness 2.5 to 3. Lustre metallic. Colour pure white, labial veil is covered with papillæ, and provided with a small except when tarnished. Streak shining. Opaque. Specific barbule on each side. The belly is not protected by plates. gravity 10:47. Malleable, but commonly less so than pure The species are found in the rivers of South America. In silver, probably owing to an admixture of other metals. the second subgenus, to which Lacépède restricts the term Soluble in nitric acid, and the solution colourless when Loricaria, there is but one dorsal fin; the labial veil is fur- pure, but blue if copper be present; and if antimony, a nished with several barbules, and sometimes beset with white substance, and if gold, a black one remains undisvillosities; the belly is protected by plates. The species of solved. Fuses into malleable globules before the blowpipe. this section are also found in South America.

Native silver is met with in most parts of the world. in SILVA Y FIGUERO'A, GARCIA DE, was born of the British Isles, Germany, Hungary, in the north of illustrious parents at Badajoz, in 1574. At the age of Europe, but especially, and in largest quanuity, in Mexico fifteen his father sent him to court, where he entered the and South America. Silver occurs in mixture or comhousehold of Philip II. as page. He then joined the bination with other metals, as already hinted at. The first Spanish army in Flanders, where he greatly distinguished courpound of this nature we shall describe is himself, and obtained the command of a company. Having Antimonial Silver. Stibiuret of Silver. This occurs in subsequently shown some talent for diplomacy, he was de- crystals, in grains, and massive. spatched by Philip III. on an embassy to Shah Abbás, king Primary form of the crystal a right rhombic prism. of Persia, who was willing to conclude a treaty of commerce Cleavage parallel to the terminal plane and short diagonal with Spain. Silva embarked for Goa, where he arrived in of the prism. Fracture uneven. Colour silver white, or, 1614; but the governor of that place, who was a Portu. when tarnished, yellowish white. Streak silver white. guese, fearing lest Silva's mission should lead to an inquiry Lustre metallic. Opaque. Slightly malleable. Easily into the administration of the Spanish possessions in India, frangible. Hardness 3.5. Specific gravity 9:44 to 9.8. threw every impediment in his way, and refused to provide Before the blow-pipe on charcoal readily melts, with the him with a vessel and money to prosecute his journey, as he formation of white antimonial vapour, into a greyish globule, was ordered to do. Impatient at the delay, Silva embarked which is not malleable, but eventually pure silver is obon board a native vessel and sailed for Ormuz, which port tained. It is not lotally soluble in vitric acid, oxide 'of he entered on the 12th of October, 1617. Thence he sailed antimony remaining undissolved. to Bandel (Bender Abassi) in the dominions of the Shah, The Massive Varieties are amorphous, and have a grawhen he was well received. He reached Ispahan on the nular or foliated structure. 18th of April, 1618, by the then usual route of Lar and Antimonial silver is found in clay-slale at Andreasberg in, Shiraz. After a short residence in the latter place, Silva the Harz; in Baden; near Guadalcanal in Spain ; at Salzstarted for Kazwín, or Casbin, where Shah Abbás was burg; and at Allemont in France,

.

The Andreasberg mineral (1), analyzed by Vauquelin, I investing other substances. It occurs only at Andreasberg
and the Baden (2), by Klaproth, gave the annexed re in the Harz.
sults:-

According to Klaproth, it is composed of -
(1)
(2)
Chlorine

8.28
Silver

78.0
84.76
Silver

24.64
Antimony

22:0
16.24
Alumina

67.08
100
100

100 Telluric Silver occurs in coarse-grained masses. Colour Iodide of Silver. Herreralite.-Occurs massive in thin grey.

Lustre metallic. Soft. Somewhat malleable. plates, which are silver or greyish white, and which become Specific gravity about 8'5. It is dissolved by nitric acid, bluish by exposure to the air. Transparent. Translucent and when lieated, and before the blow-pipe, or charcoal, Lustre resinous to adamantine; in thin laminæ flexible gives a fused blackish mass, containing specks of metallic and malleable. Melts on charcoal before the blow-pipe, silver.

vapour of iodine being evolved, and globules of silver It is found at the silver-mines of Savdinski, in the Altai remaining. Found at Abarradon near Mazapil, in the Mountains, Siberia.

state of Zacatecas, Mexico, in serpentine. Analysis by Rose

Sulphuret of Silver. Vitreous Silver. Silver Glance. Silver

62.42

Henkelite.-Occurs crystallized and massive. Primary Tellurium

36.96

form a cube. Fracture fine-grained and uneven; sometimes Iron

• 24

small and flat conchoidal. Colour lead-grey; blackish

99.62 when tarnished. Lustre metallic. Opaque. Hardness Native Amalgam is a compound of silver and mercury. 2.0 to 2-5. Malleable. Sectile. Specific gravity about 7.2. [MERCURY.]

When heated by the blow-pipe, sulphur is expelled and Auriferous Native Silver occurs crystallized in cubes, silver remains. It occurs in Saxony, Bohemia, and in great capillary, and disseminated. Colour yellowish white. Spe. abundance in Mexico. It has been occasionally found in cific gravity 14.0 to 17.0). Different varieties gave the Cornwall, and in most silver-mines. annexed results to

Analysis, (1) by Klaproth, of a specimen from Freiberg;
Fordyce. Klaproth.

Boussingault.
(2) by Berzelius :-

(1) (2) Silver 72 34 15.5 17.6 26 35:07

Sulphur

15 12.95 Gold 28 64 84.5 82.4 74 64.93

Silver

85

87.05 100

100 100

98 100 100 100 100 Arsenical Antimonial Silver, or rather Arsenio-ferru- Derived from the decomposition of the last mentioned.

Black Sulphuret of Silver. Earthy Silver Glance.ginous Antimonial Silver.—This substance occurs mammillated or in small globular and reniform masses, and dark lead-grey, inclining to black. Devoid of lustre, or

Occurs massive and pulverulent. Fracture uneven. Colour sometimes investing other substances. When untarnished it is nearly silver white, but is commonly tarnished yellowish

only feebly glimmering. Somewhat sectile. or blackish; its lustre is metallic. It is harder than anti- ing, metallic. It is found in Norway, Siberia, Hungary, &c., monial silver , but is sectile and brittle. Specific gravity 9-4. usually investing other silver-ores or filling up cavities

in them. Before the blow-pipe antimony and arsenic are volatilized with the alliaceous smell, and a globule of impure silver

Sulphuret of Silver and Arsenic. Light Red Silver.

Colour cochineal remains. Its localities are nearly the same as those of

Proustite.- Primary form a rhomboid. antimonial silver. Klaproth obtained from a specimen from to aurora red; streak lighter. Lustre adamantine. TransAndreasberg

lucent to transparent. Specific gravity 5.5 to 5.6.

It is found at Joachimsthal, Johanngeorgenstadt, AnnaSilver

12.75

berg, &c. Antimony

4.00 Iron

Rose's analysis (1) and Proust's (2) give the following as

44.25 Arsenic,

35

the composition of a specimen from Joachimsthal:-
96
(1)

(2) The native compounds of silver next to be described are Sulphur 19.51 Sulphuret of Silver . 74.35 those in which it occurs in combination with the wi

Silver

64.67 Sulphuret of Arsenic 25 metallic elements. It is not found simply combined with Arsenic

15:09 oxygen, nor at all with azote, hydrogen, or fluorine.

Antimony 00.69

99.25 Chloride of Silver. Horn Silver. Muriate of Silver.

99.96 Laxmannite.--This ore occurs crystallized and massive. Sulphuret of Silver and Antimony. Ruby Silver. Dar Primary form of the crystal a cube. No cleavage. Frac- Red Silver. Braardite. Occurs crystallized and massive. ture uneven, Hardness 1.0 to 1.5. Yields to the pres- Primary form a rhomboid. Cleavage parallel to the primary sure of the nail. Streak shining. Specific gravity 4.75 to planes, usually indistinct. Fracture conchoidal. Colour, 5.55. Translucent. Opaque. Lustre resinous. Colour by reflected light, from lead-grey to iron-black; by transgrey, yellowish, greenish, and blue of various shades. Mal- mitted light, from brilliant to dark red. Lustre adamantine. leable and sectile. Fusible in the flame of a candle. Translucent. Opaque. Hardness 2.0 to 2.5. Extremely Heated with potash by the blow-pipe, yields a globule of brittle. Streak red. Specific gravity 5.8 to 5.9. metallic silver. Insoluble in nitric acid, but dissolved by Massive Varieties.- Structure granular, compact, lamelammonia. When rubbed with a piece of moistened zinc, lar, dendritic, amorphous. the surface becomes covered with metallic silver.

It is found in many parts of Europe and America, as This ore oc rs in various parts of Europe and America, Germany, Norway, Mexico and Peru, and also in Cornalong with others of the same metal. The largest masses, wall. which are of a greenish colour, are brought from Mexico According to Bonsdorff, a specimen from Andreasberg and Peru. It is found in veins, chiefly in primitive rocks. yielded by analysis Two specimens from Peru (1) and from Saxony (2), ana

Sulphur

16.609 lyzed by Klaproth, gave

Silver .

58.949
(1)
(2)
Antimony

22.846
Chlorine.

24

21.50 Silver

76
67.75

98.404
Oxide of Iron

6.00

Sulphuret of Silver and Antimony. Miargyrite.-Occurs Alumina

1.75

crystallized. "Primary form an oblique rhombic prism. Sulphuric acid

0.25

Cleavage imperfect. Fracture uneven. Colour iron-black 100

97.2 in mass; but in thin fragments deep red by transmitted light. Buttermilk Silver. Earthy Corneous Silver.- This is Nearly opaque. Lustre bright metallic. Hardness 2:0 to regarded as a variety of the foregoing. It is described as 2.5. Very sectile. Streak dark red. Surfaces of the crysbeing of a brownish colour, with occasionally a tinge of tals usually striated. Specific gravity 5'2 to 5*4. green or blue. It is opaque, dull, with an earthy fracture, It is found with argentiferous arsenical pyrites at Braunsand is soft, sectile, and heavy. It occurs massive, and also dorft, near Freiberg, Saxony.

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Rose.

According to Rose, it yielded

Bismuthic Silver.--Occurs in acicular crystals and massive.
Sulphur

21.95

Fracture uneven. Colour, when first broken, lead-grey, but
Silver

36:40

liable to tarnish. Antimony

39:14

Massive Varieties disseminated, amorphous. Fracture
Copper

1:06

fine-grained, uneven. Lustre metallic. Opaque. Soft. lron

0.62

Sectile and brittle.

99.17 It is found accompanying pyrites and galena at SchapSulphuret of Silver and a little Iron. Biegsamer Sil- pach in the valley of Kinzig, Baden. bergianz.-Occurs crystalline and massive. Crystals small Analysis by Klaproth:and tabular. Cleavage parallel to the terminal planes.

Sulphur

16.3 Colour nearly black. Lustre metallic. Very soft. Readily

Silver

15.0 separable into thin flexible laminæ.

Iron

4.3 Found only in Hungary and at Freiberg.

Copper

0.9 According to Wollaston, this mineral (which is extremely

Bisnuth

27 rare) consists of sulphuret of silver with a little iron.

Lead

33 Sulphuret of Silver and Iron. Sternbergite. Flexible

96.5 Sulphuret of Silver.-Occurs crystallized. Primary form Seleniuret of Silver. Selensilver.-Occurs crystallized. a right rhombic prism. Cleavage parallel to the terminal Primary form a cube. Occurs in thin plates. Hardness plane, distinct. Laminæ very flexible. Colour dark brown, between gypsum and calcspar. Flexible. Specific gravity often with a blue tarnish. Streak black. Lustre metallic. 8:0. Colour iron-black; streak the same, but brighter. Hardness 1:0 to 1'5. Specific gravity 4:2 to 4*25.

Occurs at Tilkerode in the Harz, associated with seleniuret It is found at Johanngeorgenstadt, Schneeberg, and Jo- of lead. achimstahl in Bohemia, with other silver-ores.

Analysis by G. Rose :A specimen from the last-mentioned locality yielded, ac

Selenium

24.05. cording to the analysis of Zippe

Silver

65.56 Sulphur

30

Seleniuret of lead, with a little iron 6.79
Silver
33.2

96-40
Iron

36

Seleniuret of Silver and Copper. Eukairite.- Occurs 99.2

massive. Structure granular. Colour grey. Lustre shiuBrittle Sulphuret of Silver, Antimony, and Iron. Brittle ing: Disposed in films on calcareous spar. Silver Glance.-Oecurs crystallized. Primary form a right sweden.

Found in a copper-mine at Skrickerum in Smaland, rhombic prism. Crystals commonly macled. Fracture

Analysis by Berzelius :usually conchoidal, with a shining metallic lustre. Colour

Selenium

26 dark grey or iron-grey. Harduess 2:0 to 3. Specific

Silver

3893 gravity 5.9 to 6.4.

Copper

23:05 It is found in Saxony, Bohemia, Hungary, Siberia, and

Earthy matter

8.90 Mexico.

Carbonic acid and loss

312 Analysis of a specimen from Frieberg by

100
Klaproth.

Carbonate of Silver and Antimony. Selbite.-Occurs
Sulphur

12
16:42
massive and disseminated. Fracture uneven.

Colour
Silver

66.5
68.54

greyish-black. Structure fine granular. Lustre metallic.
Antimony

10
14.68

Opaque. Soft. Brittle. Heavy.
Iron

0:00

Found at Altwolfach in the Black Forest.
Copper

0.5
0.64

Analysis by Selb:-
98.5
100.28
Carbonic acid.

12 Sulphuret of Silver and Copper. Silberkupferglanz.

Silver

72-6 Occurs massive. Compact. Fracture brilliant, granular,

Oxide of antimony and a trace of

15.5 flat conchoidal. Colour dark lead-grey. Streak shining.

copper Lustre metallic. Opaque. Soft. Specific gravity 6:25.

100.1 Found at Schlangenberg, near Colivan in Siberia.

This analysis cannot however be correct, if the ore contain Analysis by Stromeyer :

carbonate of silver. Sulphur

15.96

drseniale of Silver and Iron. Gansekothigerz; GooseSilver

52.87

dung Silver-ore-Occurs massive. Mammillated. Fracture Copper

30.83

conchoidal; sometimes earthy, and mixed with cobaltorc. Iron

00:34

Colour yellow or pale green. Sireak white. Lustre resinous.

100 Found chiefly in the mines of Clausthal in the Harz; Sulphuret of Silver, Antimony, and Copper. Romelite. and also in Cornwall, and at Allemont in France. Mine d'Argent grise Antimoniule.-Occurs crystallized. It does not appear to have been accurately analyzed. Primary form a right rhombic prism. Cleavage parallel 10. Having now mentioned the principal minerals which conthe lateral planes. Colour nearly silver-white. Lustre | tain silver, it is to be observed that few of them are largely shining, metallic. Opaque. Hardness 2 10 2.5. Ex- worked as ores: the principal are native silver, chloride of tremely brittle. Specific gravity 5.5 to 5-6.

silver, and sulphuret of silver. The first, when the quantity It consists principally of sulphur and the metals above is considerable, is separable by mere fusion; the chloride named, but in proportions not yet determined.

and the sulphuret are obtained by amalgamation with merSulphuret of Silver, Arsenic, Antimony, and Copper. cury; the sulphuret being first converted into a chloride Polybusite. Brittle Silver.-Occurs crystallized. Primary by treatment with common salt, &c. A considerable quaiiform a right rhombic prisın. Cleavage imperfect. Fracture tily of silver is also procured from the lead-ore of this uneven. Colour iron-black. Lustre metallic. Translucent. country by cupellation. Opaque. Hardness 2:0 to 2.5. Specific gravity 6.269. Occurs in Bohemia, Saxony, and other parts of Europe ;

Properties of Silver. and in Mexico and Peru.

The properties of silver are, that it has a purer white Analysis (1) of a specimen from Mexico by Rose, and colour than any other metal; it has great brilliancy, and is (2) from Freiberg by Brandes:

susceptible of a very high polish. Its specific gravity is
(1)
(2)

about 10:4 when cast, and 10.5. to 10o6 when stamped or
Sulphur

17.04
19:40

rolled. It is sufficiently soft to be cut with a knife. It is
Silver

64.29
65.50

very malleable and ductile, so that it may be beaten into
Arsenic

3:74
3:30

leaves about 1-10,000th of an inch in thickness, and drawn
Antimony

5:09
000

into wire much finer than a human hair. It does not rust Copper

9.93
375

or oxidize by exposure to the air, but when the air contains Iron

0:06
5.46

sulphurevus vapours it tarnishes, becoming first yellowisha 100.15

97.41 and afterwards black, Tbree metals only, viz. iron, copper, Sulphuret of Silver, Iron, Copper, Bisnuth, and Lead. / and platinum, exceed silver in tenacity; a wire 0.787 of 1

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line in diameter supports rather more than 187 pounds It is composed of without breaking. When exposed to a bright red beat

One equivalent of chlorine .

36 silver melts, which, according to Daniell, is equivalent to

One equivalent of silver

108 18730 of Fahrenheit; on fusion its appearance is extremely brilliant, and during this it absorbs oxygen from the air to the

Equivalent 144 amount of about 22 times its volume, and this it gives out Chloride of silver is largely and advantageously used either by cooling or by being poured into water. When leaf. both in qualitative and quantitative analyses, to determins silver or fine silver-wire is heated by voltaic electricity, it the presence and quantity of chlorine, chlorides, and hydroburns with a fine green flame; if intensely heated in the chlorates. open fire, it boils, and a portion is vaporized.

Fluorine and Silver may be combined to form fluoride of Oxygen and Silver combine to form three compounds, silver. It is an uncrystallizable soluble compound; when viz. suboxide, protoxide, and peroxide.

heated it fuses; and at a higher temperature and exposed Protoxide of Silver is prepared by oxidizing and dissolv- to the air it is slowly reduced. ing the metal in dilute nitric acid; when lime or baryles It is composed of water, or solution of potash or soda, is added to the solution

One equivalent of fluorine .

18 of nitrate of silver, a precipitate is formed, which is the prot

One equivalent of silver

108
oxide of silver, composed of
One equivalent of oxgyen
8

Equivalent 126
One equivalent of silver

108

Sulphur and Silver form sulphuret of silver; this com

pound has been already noticed as existing in nature and Equivalent 116

constituting the vitreous silver-ore. It may be prepared by The properties of this oxide are, that it is of a brownish direct action, as by healing alternate layers of silver and colour, inodorous, tastless, very slightly if at all solubie in sulphur; thus obtained, it is a soft malleable dark-coloured water; it is decomposed by the action of light, being reduced compound; it may be procured also by decomposing soluto metallic silver and oxygen gas, and the same effect is tion of nitrate or of ammoniuret of silver by hydrosulphuric produced by heat. It is insoluble in the alkalis or alkaline acid, hydrosulphates, or soluble sulphurets. It is insoluble earths in general

, but is rapidly and largely dissolved by in water, ammonia, or other alkalis or acids, except nitric ammonia. Nitric, acetic, sulphuric, and some other acids acid, which decomposes and is decomposed by it with the combine with it readily, but it is decomposed by hydro- formation of sulphate of silver. chloric acid, the results being chloride of silver and water. It is composed of It gives a yellow colour to glass and porcelain. This is the

One equivalent of sulphur

16 oxide which is the basis of all the common salts of silver.

One equivalent of silver

108 Suboride of Silver was first procured by Faraday, by the partial decomposition of the protoxide; when the ammonia

Equivalent. 124 cal solution of this is exposed to the air, its surface becomes Phosphorus and Silver.-The sesubstances combine when covered with a pellicle or dark film, which is the suboxide in heated together; and form a while brittle compound; when question; it is probably owing to the decomposition of a fused and exposed to the air, it loses phosphorus. It may be portion of the ammonia, which in this case yields hydrogen formed either by projecting phosphorus on red-hot silver, to a part of the oxygen of the protoxide of silver.

or by heating a mixture of silver filings, phosphoric acid, According to Wöhler, it may be obtained also by subject and charcoal. ing citrate of silver to a temperature of 212°.

It is composed of
Suboxide of silver appears to be a di-oxide, composed of -

One equivalent of phosphorus 16
One equivalent of oxygen

One equivalent of silver
Two equivalents of silver
216

Equivalent 124
Equivalent. 224

Iodine and Silver readily combine when hydriodic acid It does not readily, if at all, form salts with acids. or jodide of potassium is added to a solution of nitrate of

Peroxide of Silver has been stated to be obtained by elec- silver. The iodide of silver formed is precipitated of ą trizing a weak solution of silver. It separates at the positive greenish-yellow colour: it is insoluble in waier or ammonia, pole in the state of minute acicular crystals.

and decomposed when heated with potash; when fused, it Sulphuric and phosphoric acid decompose it with forma- acquires a red colour, and is discoloured by light; in the tion of respective salts of the protoxide, and by ammonia it invention of the Daguerreotype, a film of this compound, on is acted upon and decomposed with great energy.

the surface of a polished plate of silver, is the substance It appears to be a binoxide, composed of

that receives the impressions of light. It is decomposed by Two equivalents of oxygen

16

concentrated nitric or sulphuric acid. One equivalent of silver

108

It is composed of
One equivalent of iodine

126
Equivalent 124

One equivalent of silver

108 Chlorine and Silver readily combine, and the compound, as already mentioned, forms one of ore of silver.

Equivalent 234 · It may be artificially formed in sereral ways, first by leat The compounds containing oxide of silver consist of the ing the metal in a finely divided state in the gas, or by ammoniuret and the oxisalts of silver: we shall first mention adding any soluble chloride, as common salt, to nitrate or the any soluble salt of silver, except the hyposulpbite.

Ammoniuret of Silver. -Protoxide of silver dissolves with When recently precipitated, or if kept from the action of great readiness in ammonia, and by careful operation the Jight, chloride of silver is perfectly white, but by exposure to substance discovered by Berthollet, and called fulminating daylight it becomes slowly bluish-white, and eventually silver, is obtained. It should be prepared only in very small altaost black. The direct rays of the sun produce this effect quantity at a time, on account of the facility and violence almust instantaneously; on this property is founded its use with which it explodes ; in exploding it forms water, sets in photogenic drawing: the exact nature of the change which free azotic gas, anil metallic silver, remains ; it is procured by takes place does not appear to have been satisfactorily adding a small quantity of solution of ammonia to oxide of determined. This chloride is quite insoluble in water, either silver; a portion is dissolved, and a black powder, which is cold or hot; the stronger acids take it up sparingly, and it is the fulminating ammoniuret of silver remains; it may be precipitated from them by dilution; it is dissolved however also formed by adding solution of potash from the ammonioto some extent by hyposulphurous acid, and readily and nitrate of silver; a very gentle heat or slight friction causes. largely by ammonia. It is decomposed by hydrosulphuric it to explode, sometimes even before it is dry. Its exact. acids, and soluble sulphurets, which immediately blacken it composiiion has not been determined. by converting it into sulphuret of silver; it is also decom We come now to the compounds of the oxacids and oxide: posed by hydrogen gas, and by iron and zinc when put into of silver, or the oxisalts of silver; it is the protoxide only contact with it and water. By mere heat it undergoes no which enters into combination with acids; at least they are: change except fusion, and when it has solidified on cooling, the only well-known compounds. The first we shall menit has the appearance of horn; hence the name of horn silver tion is for the native chloride.

Nitrate of Silver. - This is one of the most important

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108

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