SILURIAN ROCKS-SILURIDE. The Silurian system contains an enormous thickless of rocks, nearly 30,000 feet, according to some estimates, the absolute thickness being greatly increased by immense beds of interstratified igneous tocks. The upper limit, underlying the Old Red Sandstone, is universally accepted, but there has been considerable diversity of opinion in regard to the inferior boundary. Professor Sedgwick, having lescribed the rocks of North Wales, which at first were considered to be older than the series which Murchison had illustrated, designated them Cambrian. This name has been retained for the immense mass of indurated shales and sandstones of a thickness nearly equal to that of the Silurians, which contain only faint traces of organic life, and underlie the Llandeilo formation. But Sedgwick claims also the Lower Silurian rocks as a portion of his system; the priority of name, and the uniform facies of the organic remains of the whole of the Silurian rocks, have, however, induced geologists to consider the limits as originally given by Murchison as those of the system. The subdivisions of the rocks of the period are the following: 80 to 1000 150 900 of the same age as the corresponding strata iz north of Scotland. On the continent, Silurian strata have bes examined and co-related with the British tipes a Bohemia, by M. Barrande; in Scandinavia, by M Angelin; and in Russia, by Murchison and others In North America, also, extensive regions are covered with these strata. They have been wrought out and their fossils described by the Canadian and United States surveyors. Similar strata have am been detected in India, Australia, and South America. The life of the period presents a group of ver characteristic organisms, which, with the exept a of the fish-remains found in the upper bes, al belong to the invertebrata. Many of them are o fined to the Silurian rocks, or occur only very rarey in some of the Paleozoic formations. The Gra lites are a strictly Silurian family of Zoophytes, and most of the forms of Trilobites are found orym this period, though some members of the tribe are found in rocks of Devonian and Carbonif rous at Besides these, may also be specified such forms as Heliolites and Favosites among the Corals; Actin crinites and the Cystidians among the Ect> derms; Orthis and Lingula among the B-sch RWŽA, Thickness in Feet and Lituites and Maclurea among the Cephalant In all the immense thickness of Silurian roke, mo 800 deposit has been discovered containing or ataTa that have lived on land. Some fragments have been noticed that have a faint resemblance to the branches of Lepidodendron, and minute bodeg occur in the bone-bed, which are referred to the spores of a terrestrial cryptogam. The only o 1400 indications of plants are impressions believedt hom been produced by sea-weeds. The anthraciti, sh of Wales and Scotland probably derived thy anthracite from the algae that must have abans ! in the Silurian seas. In Shropshire, a number 800 shells have been found, whose nearest allies a littoral species, and these appear to ina ate the 1000 existence there of an ancient shore. The Sara rocks are, however, generally sea-deposits, and Forbes has ingeniously shewn, from the small 26 € the conchiferæ, the paucity of spiral univalves, the great number of floating shells and of the pract Örthida, and the great rarity, or absence, ex»;" a 1500 the upper beds, of fossil fish, that it is most prac they were deposited in a sea more than 70 Lath deep. 7. Woolhope Limestone and Denbighshire Grit, 8. Tarnnon Shale, 9. May-hill Sandstone and Pentamerus Limestone, MIDDLE SILURIAN ROCKS. Upper Llandovery 300 150 1000 12,000 5800 The typical Silurian strata are in Wales, and the SILURIDÆ, a family of malacopteroas. És adjoining English county, Shropshire. With the divided into many genera, and including a great exception of the southern and south-eastern districts, number of species, mostly inhabitants of the late where the Old Red Sandstone and Coal Measures and rivers of warm countries. The S. exh but great occur, the whole of Wales is composed of Silurian and diversity of form. Their skin is generally nik-t, Cambrian rocks. The same deposits are found in Cum- but some have a row of bony plates along the latera berland and the north of Lancashire. The whole of line, and a few are completely mailesi with bar Scotland south of a line drawn from Dunbar on the plates. The dorsal fin is single in some, ott a east to Girvan on the west, consists of graywacke have two dorsal fins, the second being sometas rocks, slates, and limestones of Silurian age, with adipose, as in the salmon family. The dorsal to a the exception of one or two small patches of Old sometimes armed with a strong spinous ray asi 1 Red, Carboniferous, and Permian strata. The most of the family the first ray of the pectina a rocks, till recently referred to an azoic group, below is very strong and serrated, so as to be caps @ 1 the lowest fossiliferous strata in the north of Scot-inflicting a severe wound, and by this the a land, are now generally believed to be highly are protected from alligators and other camis altered beds of this period. The southern boundary All have the mouth furnished with barne & # of these beds is a line drawn from Stonehaven to less numerous; the two principal barbels thug m Helensburgh. A huge trough, filled up with Old the upper lip, and formed by elongation of the cate Red Sandstone and Carboniferous strata, separates maxillary bones. The barbels are bein, tim the highly altered strata of the north from the less organs of touch, probably of use in directing t- a altered deposits of the south. An extensive region to its prey. The bones of the head ani ot of Silurian rocks occurs in the south-eastern coun- of the skeleton exhibit many peculiant s ties of Ireland and in Galway; and a great track which we cannot enter. The & are of the same beds extends from the centre of Ireland inhabitants of muddy rivers, lurking ameta (Cavan, &c.) to the coast of Down. The metamor- mud. The only European species is the SLYN, PA phic rocks of the north-west are most probably also SHEAT-FISH, or SHADEN (Silurus glans, tie larg SILVAS-SILVER. of European fresh-water fishes, and sometimes found in the sea near the mouths of rivers. It does not inhabit any of the rivers of Britain; its introduction has, however, recently been attempted. Neither is it found in France, Spain, or Italy, but it is plentiful Sly Silurus (Silurus glanis). of only roth of an inch, and one grain of the metal being capable of yielding 400 feet of wire. It possesses a high degree of tenacity, a wire with a diameter of th of an inch being able to support a weight of nearly 188 pounds. It requires a heat of 1873° Fahr. to fuse it, and on cooling, expands at the moment of solidification. It is an excellen conductor of heat and electricity, and is not affectea by exposure even to a moist atmosphere at any temperature. When, however, it is fused, it absorbs a considerable quantity of oxygen, which it expels in the act of solidification with a peculiar sound, technically known as spitting." But although it does not rust or become oxidised, it usually becomes tarnished on prolonged exposure to the air, owing to the formation of a film of sulphide (or sulphuret) of silver, and this change occurs more rapidly in towns than in the country, in consequence of sulphuretted hydrogen being more abundant in the atmosphere of the former than of the latter. This metal is unaffected by the hydrates or nitrates of the alkalies, even at a high temperature, and hence silver crucibles, &c. are highly useful in many laboratory operations. in the Danube, the Elbe, and their larger tributaries, also in the rivers which fall into the Caspian Sea; and it is found in some of the rivers of North America. It attains a length of six or even eight feet, and a weight of 300 or 400 pounds. The flesh Hydrochloric and dilute sulphuric acid have is white and fat; but soft, luscious, and not very scarcely any action on silver, but nitric acid and easily digestible. In the northern countries of Europe, boiling sulphuric acid oxidise it, and form salts; it is preserved by drying, and the fat is used as lard. nitric acid being by far its best solvent. Silver has The habits of the fish are sluggish; it seems rather strong affinities for chlorine, bromine, iodine, and to lie in wait for its prey than to go in quest of it.-sulphur, and combines with the first three and sulSeveral species of this family are found in the Nile, phuretted hydrogen at ordinary temperatures. It is among which is the HARMOUTH or KARMOOT (Clarias well known that common salt, especially in the anguillaris), a fish in its general form and appear- melted state, when left for any time in contact with ance much resembling that just described. It was silver, corrodes that metal, soda being formed from anciently an object of superstitious regard in the the oxygen of the air, while the liberated chlorine Thebaid. attacks the silver. crystallised in cubes or octahedrons, or occurring in Silver is frequently met with in the native state, fibrous masses. It is also found in combination &c., and sulphide of lead is almost always accomwith gold, mercury, lead, antimony, arsenic, sulphur, silver; it is, however, never found as an oxide. panied with a greater or less amount of sulphide of SILVAS, or SELVAS (Span. selva, a forest), the name given to the western portion of the great plain of the Amazon, in the north-west of Brazil. The Silvas, which are about one-third of the whole plain, contain more than 700,000 English sq. m., and consist of low land on a dead level, densely covered with primeval forests, and annually inundated by the overflow of the mighty river or its tributaries. viz., a suboxide, Ag0; an oxide, AgO; and a perSilver forms three compounds with oxygenThe forests are rendered wholly impenetrable from oxide, AgO. All these oxides possess the common the denseness of the underwood, matted together as properties of being reduced by heat to the metallic it is by creeping and climbing plants, which form myriads of festoons glowing with nature's brightest state, and of being very readily decomposed by the tints. The vegetation of the Silvas, under the stimu- action of light. The oxide, AgO, is the only one of lating action of the abundant irrigation, the intense dark-brown heavy powder, devoid of taste or smell, these compounds requiring special notice. It is a tropical heat, and the inconceivable richness of the somewhat soluble in water, to which it communialluvium which constitutes the soil, shews an exuberance of growth far surpassing that of any other cates a metallic taste and an alkaline reaction. It portion of the earth's surface, and from its very acids, and forming normal salts with them. It acts as a powerful base, neutralising the strongest luxuriance, presents a bar to civilisation no less is obtained by the addition of a solution of potash effectual than do the barren deserts of Africa or the to a solution of the nitrate or any other soluble gloomy wastes of Central Asia. The few Europeans salt of silver, falling as a hydrated oxide, which, who have penetrated into this region have sailed up the Amazon and some of its tributaries, and from them we have received the little knowledge that we do possess of this immense tract of wild forest. It is the haunt of innumerable wild animals, especially monkeys and serpents, and of a few aboriginal inhabitants, who are sunk in the lowest stage of barbarism. SILVER (symb. Ag, equiv. 108, sp. gr. 10:53) is a metal which, in its compact state, is of a brilliant white colour, possesses the metallic lustre to a remarkable degree, is capable of being highly polished, and evolves a clear ringing sound when struck. It is harder than gold, but softer than copper, and is one of the most ductile of the metals. It is malleable, may be hammered into very thin leaves, and may be drawn out into very fine wire, the thinnest silver-leaf having a thickness at a temperature above 140°, becomes anhydrous. If a concentrated solution of ammonia be digested for some hours upon freshly precipitated oxide of silver, Fulminate of Silver (q. v.), or Fulminating Silver in the form of a black powder is produced, and the same dangerous compound is formed when an ammoniacal solution of nitrate or chloride of silver is precipitated by potash. The salts which the oxide of silver forms with acids are characterised by the readiness with which they decompose, the mere a tion of light blackening and partially reducing them. None of these salts occur in nature. The following are the most important of those which have been formed artificially. Although ordinary air has no oxidising action on silver, ozonised air rapidly attacks it. SILVER. Nitrate of Silver (AgO,NO) crystallises in large, clourless, transparent square tablets, which blacken on exposure to light, or in contact with organic matters, owing to reduction, and dissolve in their own weight of cold water. This property of producing a permanent black colour with organic matters has led to its employment as a marking ink for linen, &c. The black stains which it forms on the skin, on linen, &c., may be removed by the employment of a strong solution of iodide of potassium, or more readily by a solution of cyanide of potassium. The crystals fuse at a temperature of about 425°, and the molten mass, when cast into cylindrical moulds, solidifies, and forms the sticks of lunar caustic which are employed in surgery, medicine, and Photography (q. v.). Nitrate of silver is prepared by dissolving pure silver in moderately strong nitric acid, and evaporating till the solution is sufficiently concentrated to crystallise. The most characteristic test for the salts of silver is the action of hydrochloric acid, or of a soluble chloride, which produces a white curdy precipitate of chloride of silver, insoluble in nitric acid, but readily soluble in ammonia: it is also soluble in hyposulphite of soda, with which it forms an intensely sweet solution; cyanide of potassium also dissolves it; the chloride of silver speedily assumes a violet tinge when exposed to light.'-Miller's Elements of Chemistry, 2d ed., vol. ii. p. 732. Of the haloid salts of silver, several occur native. The most important of these compounds is chloride of silver (AgCl), which is found native either in cubes or in a dense semi-transparent mass, and is known as horn silver, and may be procured as a dense white flocculent precipitate by the procedure described in the preceding paragraph. In consequence of its sensibility to light, it is employed in photography. When heated to about 500°, it fuses into a yellow fluid, which, on cooling, solidifies into a yellowish gray semi-transparent horny mass. This salt is insoluble in water and in all the diluted acids, but dissolves in a solution of ammonia, from which it crystallises in octahedra. Its solution in a solution of hyposulphite of soda is employed in silvering iron, copper, and brass goods. Traces of this salt are found in sea-water, the chloride of sodium probably acting as the solvent. Bromide of silver (AgBr) is found in Mexico, where it is known as Plata verte, or green silver, in the form of small crystals or crystalline granules of a pale olive-green tint. Iodide of silver (AgI) occurs native in several Mexican mines in the form of thin, flexible, pearly scales. Sulphide (or sulphuret) of silver (AgS) is the principal ore of silver. It occurs native, sometimes crystallised in cubes or octahedra, and sometimes in masses. From its gray metallic lustre, it has received from mineralogists the name of silver glance, It is well known that if silver spoons are allowed to remain in contact with boiled eggs for some time, they become tarnished by the action of the suphur; a minute quantity of sulphuretted hydrogen being probably evolved. The discoloration is easily removed by washing the darkened silver Brande gives the following directions for preparing marking ink: Dissolve two drachms of nitrate of silver and one drachm of gum-arabic in seven drachms of water, and colour the liquid with Indian ink. The cloth must be first prepared by moistening the spot with a few drops of a soda solution, prepared by dissolving two ounces of crystallised carbonate of soda and two drachms of gum in four ounces of water. Professor Miller recommends, as a cheap indelible marking ink, a solution of coal tar in naphtha; it resists the action of chlorine, and is used by bleachers to mark their goods. with a solution of cyanide of potassium. Sale of silver unites with various other metallic sup. when fused with them, especially with the su of arsenic and antimony. Red silver ore (3.Agymg is a native compound of this kind. The alloys of silver and copper (see ALST and MINT), when cast into ingots, are many found to differ in their composition in the internil and external parts, in consequence of a molecu change that takes place during the cocing and slow solidification of the molten mass In containing more than 719 parts of silver in low, the central portions are richer in silver than exterior; in alloys of less value, the reverse observed, while in ingots containing 9 more parts of silver in 1000, the ext is nearly uniform throughout. When exactiv parts of silver and 281 of copper are com (corresponding to the formula AzCu), nɔ servaration whatever of the metals occurs. Many met as tin, zinc, antimony, bismuth, arsenic &c, w», mixed with silver, render it brittle and u..t its ordinary uses; they are, however, easily ring v in the process of refining. An alloy consistan five parts of silver, six of brass, and two of m is used as a solder for silver. An alloy of silver an mercury, known as silver amalgam, occurs native s a crystallised form. It is a mineral of a a white colour, and its composition is repres uted ly the formula, AgHg. Silver, like gold, has been known and pris! - m the earliest ages. Its production is not at ill k-p ing pace with the new discoveries of gold Tie richest silver mines in the world are the iẻ Mexico, the estimated annual yield of w. about 1,600,000 lbs. troy of the pure metal is next in importance, but its pro lue is not m than a fifth or a sixth that of Mexion, Ca Bolivia have also considerable silver mines America, with the exception of Mexico, has Litterte furnished only a small quantity; but a rus rich silver ores from California was shewn in t last great Exhibition (182) in London, wis how re said to be obtained from veins so extens ve 29 20 encourage the hope of its silver mines becs -scarcely less famous than its gold-bearing a' ava deposits. The total silver produce of North and South America is a little over 2,000,000 Is try annually. Of European countries, Spain is the most prolom tive in silver. In the district of Guadilaxara, & ma new mines were opened a few years ago, w'un tarɛ already reached a degree of prosperity quite extraordinary, the vein upon which they are placed taining, curiously enough, large quantities of a = ver ore, called freislebenite (a compound of si am antimony, lead, and silver), which has been ! teta looked upon as a very rare natural suistan e Nrt to Spain, Austria, Saxony, and the Herz distrita Northern Germany, yield the largest suprbes Te silver mines of Kongsberg in Norway are ¦ kem valuable, and have been long famous. "Great Retam has no silver mines, properly so callesi, ol extent; but since the introduction in 199 Pattinson's process for the desilverising of lead smelted from argentiferous galena, a large qurame has been annually obtained in this way, the j in 1864 being 641,088 ounces. (See Lian) ́I= mineral veins of Cornwall, some bunches of ra silver ores have recently been found, but of limits th extent. The forms in which silver is found in natuTM numerous, but we need only notice a few of ten It is frequently found native in crystal 1 amorphous masses, which are sometimes s ¡able size. One fine piece found at kungsartg SILVER. now in the Copenhagen Museum, and weighs 500 lbs. But the quantity of silver found in nature in the metallic state is comparatively small. Its principal ores are the different sulphurets-viz., silver glance, or sulphuret of silver, containing when pure 87 parts of silver and 13 of sulphur; brittle silver ore, or sulphuret of silver and antimony, of which the composition is, silver 68 5, antimony 147, and sulphur 164; and red silver ore, called also ruby silver, of which there is a dark and a light kind, the composition of the former being similar to brittle silver ore, but it is a little less rich in silver, and the latter only differs in containing arsenic instead of antimony. The bulk of the silver obtained in Mexico and South America is got from these ores. The only other of much importance, except the mixed ores to be presently noticed, is horn silver, or chloride of silver. In a pure state, it consists of silver 75, and chlorine 25. It occurs extensively in Mexico and Peru, but is not common in European mines. Besides the ores named above, a good deal of the silver of commerce is obtained from mixed ores, that is, the ores of other metals are frequently found to contain it. In many cases, the amount of silver falls greatly short of 1 per cent. These ores are for the most part sulphurets of tin, arsenic, copper, iron, and lead. In the reduction of silver ores, the processes followed are based upon the fact, that both lead and mercury have a strong affinity for silver. A more recent process depends upon the solubility of chloride of silver in a hot solution of common salt, and its separation again on cooling. The simplest process is ordinary smelting, and is only applied to the richest ores. These are crushed, mixed with old slag, lead in some form, and a little iron ore and lime. The mixture is then heated in a furnace with charcoal, which brings down the silver and lead together as an alloy. The silver is afterwards easily separated by cupellation, the principle of which is described in the article ASSAY; but on the large scale, instead of a small bone ash cupel, a cupellation furnace, say 6 feet in diameter, is used, of which fig. 1 is a section. Here Fig. 1.-Silver Cupellation Furnace. plan, called the amalgamation process, is more commonly adopted. The following is an outline of the way in which this is practised at Freiberg in Saxony. Ore consisting chiefly of silica, with but little lead, copper, &c. as sulphurets, and only from 3 to 34 oz. of silver per cwt., is ground to powder by machinery, described under METALLURGY; but a large propor tion of sulphuret of iron is also present, or must be added. About 10 per cent. of common salt is then mixed with the ore, and the mixture heated in a The Reverberatory Furnace (q. v.) to a temperature sufficient to expel water, and in part arsenic, zinc, and antimony. After two hours, the sulphur of the sulphurets takes fire, and is burned off as sulphurous acid, or converted into sulphuric acid, so that the metals become oxides and sulphates. temperature of the furnace is now raised, when the chlorine of the common salt forms volatile chlorides with zinc, antimony, and iron, and a fixed chloride with silver. During the roasting, the contents of the furnace are continually stirred, so that they ultimately form a coarse powder. The product of the roasting furnace, after being ground to a fine powder, is mixed in the proportion of 10 cwt. with 3 cwt. of water and 1 cwt. of iron in fragments; the mixture being effected in oak casks made to revolve on their axes. See figs. 2 and 3. This operation lasts two hours, and effects the solution of the sulphates and common salt; and the reduction of the chloride of iron and the chloride of copper to subchlorides-a change required in order to prevent the formation of subchloride of mercury in the next stage, which would be lost, and the principal part of the process, the merso cause a waste of quicksilver. Next follows curialising. Quicksilver to the amount of 20 cwt. is made to run into each of the casks, which are then set in motion, and continue for 22 hours at the rate of 12 revolutions per minute. The result of this is the reduction of the chloride of silver in presence of the metallic mercury, with which the silver forms an amalgam. a, sole formed of wood ashes; b, bricks; c, bed of slag; d, dome of iron plate; ee, tuyères for bellows; f, fireplace; g, crane for lifting doine the alloy is melted, bellows are used to remove the lead as litharge, or oxide of lead, and a cake of silver is left on the cupel forming the bottom of the furnace. It happens that not many even of the richer ores are pure enough to be treated with advantage by simply roasting them with lead; accordingly, another In order to separate the amalgam from the earthy 1 SILVER. matters and the sulphates and chlorides, the barrels, which were hitherto only two-thirds full, are now filled with water (the dilution throwing down any chloride of silver held in solution by the sea-salt), and kept revolving for two hours; after which, by Fig. 3.-Plan of Part of Amalgamating Apparatus. means of a stop-cock, the amalgam is allowed to flow into the amalgam chamber, and the rest of the contents, except the iron fragments, into a washtun. The superfluous quicksilver has next to be separated from the amalgam. This is done in bags of ticking, through which the mercury at first flows readily by its own weight, and is afterwards squeezed out on a flat surface. The result of this operation is, that the amalgam of mercury, silver, copper, &c. is left in the bags: its actual composition being nearly 85 per cent. of mercury, 10 per cent. of silver, and 5 of copper, lead, and antimony. Finally, the quicksilver of the amalgam itself is separated by heat in the distilling furnace, fig. 4. Here the Fig. 4.-Furnace for Distilling the Amalgam. a, iron retort: b. iron pots; c, fireplace; d, flue; f, condensing pipe; g, trough for collecting mercury. amalgam is put into a row of iron pots, which go into a large retort. When heat is applied, the quick silver volatilises, and is condensed in a pipe attached to the retort, from which it is collected in a trough. The impure silver left in the retort is refined by fusion and subsequent cupellation. There is another process carried on at Freiberg and elsewhere, by which the use of mercury is dispensed with. It consists in treating the ore as above described till it leaves the roasting-furnace. At this stage, the roasted ore is digested in a warm concentrated solution of sea-salt, which readily dissolves the chloride of silver. On diluting the solution, and allowing it to cool, the chloride of silver will separate again, and could thus be obtained as a compound of comparative purity. But it is found preferable, instead of diluting the liquid, to intro duce metallic copper, which has the property of decomposing the chloride of silver: the che unites with the copper to form chloride of oupper, and the silver is precipitated. In Mexico, the extraction of the silver from its ores is chiefly accomplished by amalgamation, bat the plan employed differs a good deal from the ar process described above, and is more primitive and wasteful, owing to the formation of subchion le of mercury. It is estimated that as much as 6,000 cwt. of quicksilver has been lost in this way at the American mines in the course of 200 years. It has now become a common practice at Swa where the great British copper smelting works are situated, to extract the silver which exists in an appreciable, though small quantity, in many es er ores. Several processes are followed, but it wil suffice to name the liquation process. Bl.-ter copper, that is, copper unrefined, which has a smelted from an argentiferous ore, is melted with three or four times its weight of lead, and cast 10 ingots. When these are moderately heated, ti copper does not fuse, but the lead and silver melt, and run off together. The lead is t separated from the silver in the usual way by cupellation. The physical and chemical properties of silver are such as make it specially valuable for many pr poses in the arts; the chief of which are not the articles Alloy, Mint, Plating, Galvan.sin, and Photography. Ordinary mirrors have their ing produced by a coating of an amalgam of ta and mercury; but a process has for some years been practised, by which a mirror-like cot ng of silver is given to glass objects of any round as w. 38 flat form. It consists in mixing some of the salts dĺ silver, usually the nitrate, with an alcoholic solat. a of grape-sugar or of certain essential oils, whet has the property of reducing the silver to the metal lic state, and depositing it on the surface of the glass. 12 15 MEDICINAL USES OF SILVER. Nitrate of it. in small doses, constitutes an excellent tone, asi t appears to exert almost a specific influence over certain convulsive diseases. As a tonic, frequently prescribed in the early stages of p.ti. and in cases of irritability of the mucous metrase of the stomach; and epilepsy and chorea fre yield to its influence, when many other re have been tried in vain. There is unfortunate t great drawback to its administration-viz, when its use has been continued for some this salt communicates a permanent slate i bluish-gray hue to the skin. There is very danger of this change of colour occurring of the medicine is not administered for a longer per d than three months. In prescribing this sait, its usual to begin with a small dose, about ones 1. a grain, and gradually to increase it to two or t grains, three times a day. It is best aim n.st. in pills made with some vegetable extract surgical uses of nitrate of silver have been almay noticed in the article on LUNAR CAUSTIC. Oxide of silver is employed in the same case the nitrate. It is especially recommended in car exc affections of the stomach, and in menorrha, I may be given in the same doses as nitrate. of silver has been employed both in America 2: a Germany in the same cases as the nitrate, an a certain forms of syphilitic disease. It is state t to produce the discoloration of the skin causes t the nitrate; but as the same statement was a dently made regarding the oxide, and was fou to be fallacious, we are not inclined to put any a.th in this assertion, especially as the nitrate must be |