METALS 



METAL-WORK 



151 



with a tendency to blue or gray. Most of them 

 have been obtained in crystal*, and probably all of 

 them are capable of crystallising under certain 

 conditions. (4) Metals are remarkable for their 

 opacity, except when they are chemically reduced to 

 extremely thin films. (5) All the metals are fusible, 

 although* the temperatures at which they assume 

 the fluid form are very different (see MELTIXO- 

 l-uiN'T) ; and some of them, as mercury, arsenic, 

 cadmium, zinc, &c., are also volatile. (6) Great 

 weight, or a high specific gravity, is popularly but 

 erroneously regarded as a characteristic of a metal ; 

 while platinum, osmium, and indium (the heaviest 

 belies known in nature) are more than twenty 

 times as heavy as water, lithium, potassium, and 

 sodium are actually lighter than that fluid. 

 (7) Great differences are observable in the hard- 

 ness, brittleness, and tenacity of metals. While 

 potassium and sodium may be kneaded with the 

 tinker, and lead may be marked by the finger-nail, 

 most of them possess a considerable degree of hard- 

 ness. Antimony, arsenic, anil bismuth are so 

 brittle that they may be easily pulverised in a 

 mortar ; while others, as iron, gold, silver, ami 

 cupper, req u ire great force for their disintegration. 

 'Hiking iron and lead as representing the two 

 extremes of tenacity, it is found that an iron wire 

 will bear a weight twenty-six times as heavy as a 

 leaden wire of the same diameter. See DUCTILITY, 



M M.LEABILITY. 



,M"ials enter into combination with one another 

 when they are fused together, and such combina- 

 tion is termed an Alloy (c|.v. ), unless when mer- 

 cury is one of the combining metals, in which case 

 the resulting comjxiund U termed an AIHH/I/IHH 

 (q.v.). It is doubtful whether all alloys are true 

 chemical compounds. Definite compound! of the 

 metals with each other do, however, certainly 

 exist, and are sometimes found native, as, for 

 example, the crystallised silver and mercury com- 

 pound represented l>v the formula AgHg. 



In consequence of their strong affinities for the 

 metalloids the metals are seldom found in a free or 

 iincotnbined state, even in the inorganic kingdom, 

 and never in animals or plants. The more common 

 metals, in consequence of their strong affinity for 

 oxygen and sulphur, are very rarely met with in 

 the iincombined state ; but some of those which are 

 less abundant, such as gold, silver, and platinum, 

 are found uncumhined, in which case the terms 

 iitili'i-r and finjin are applied to them ; and other 

 metals, as mercury and copper, occur both in a free 

 and in a combined state. Many native alloys are 

 found, but the ordinary sources of the metals are 

 oxides, sulphides, chlorides, and cjulnmates, sul- 

 phates, ano other salts. These are termed the ores 

 of the metals. The method* of obtaining the 

 metals from their various ores fall under the head 

 of MKTAI.LI'HCV. 



Various classifications of the metals have lieen 

 suggested by different chemists. The following is 

 probably one of the most convenient : 



(I.) The Light Metals, sulxlivided into 



(1) The metals of the alkalies viz. potassium, 

 sodium, ciesium, rubidium, lithium. 



(2) The metals of the alkaline earths viz. 

 barium, strontium, calcium, magnesium. 



(3) The metals of the true earths viz. alumi- 

 nium, gliicinuin, zirconium, yttiiuni, erbium, ter- 

 bium, thoriiium, cerium, lanthanum, didymium. 



(II.) The Heavy Metals, subdivided into 



( 1 ) Metals whose oxides form power fill bases 

 viz. iron, manganese, chromium, nickel, cobalt, 

 zine, eadmium, lead, bismuth, copper, uranium, 

 thallium. 



(2) .Metals whose oxides form weak ba 

 icids viz. arsenic, antimony, titanium, tantalum, 



niobium (or columbium), tungsten, molybdenum, 

 tin, vanadium, osmium. 



(3) Metals whose oxides are reduced by heat 

 noble metals viz. mercury, silver, gold, platinum, 

 palladium, iridium, ruthenium, rhodium, osmium. 

 ( Several of the rare metals are here omitted. ) 



Another classification is that by which the metals 

 are arranged in six groups, each group being named 

 after a metal which possesses the common charac- 

 ters in a well-marked degree: viz. (1) the sodium 

 group, (2) the calcium, (3) the iron, (4) the 

 copper, (5) the platinum, and (6) the antimony 

 groups. 



Metal-work, ARTISTIC. Leaving celebrated 

 statues and groups cast in bronze to be described 

 under the head SCULPTURE, we shall briefly notice 

 here a few important examples of artistic work in 

 metal which are rather classed as specimens of 

 decorative art than of pure sculpture. Of early 

 gold and silver work one of the most renowned 

 objects is the altar made of these two metals in the 

 church of St Ambrose at Milan. It was executed 

 by \Volvinus in the 9th century, and contains 

 figures in relief of Christ and the Apostles with 

 ornamental borders in enamel. Another very line 

 example of work in gold and enamel is the Palo, 

 (fOru (altar front) of St Mark's, Venice, by Byzan- 

 tine artists of the 10th or llth century. Some 

 specimens of Celtic art, partly in precious metal, 

 such as Ihe Tara Brooch and the Ardagh Chalice 

 the latter supposed to Vie of the 10th century are 

 of exquisite beauty (see BROOCH). The shrine of 

 the Magi in Cologne Cathedral is a magnificent 

 reliquary of the 12th century, in which the figures 

 are of gold and the architectural decorations covered 

 with enamels and precious stones. A considerable 

 number of specimens of ecclesiastical gold and silver 

 work of the 13th century remain, including a few of 

 great interest. Of 14th-century examples a time 

 when the goldsmith's art ceased to be employed 

 exclusively in the service of the church the 

 splendid silver reliquary in the church of Orvieto, 

 by Ugolino of Siena, is very remarkable. Perhaps 

 the two most important monuments of the gold- 

 smith's art made in the middle ages are the altar of 

 St James, Pistoia, and that of the Baptistery of St 

 John at Florence. They were begun in the 14th 

 century, and a number of the most famous Italian 

 artists were in succession engaged upon them for a 

 period of 150 years. Both are of silver, oneof them 

 being decorated with subjects from the life of St 

 James, and the other with scenes from the life of St 

 John. Giglio of Pisa, Pietro Tedesco, Ricciardi, 

 Cipriano, and Filippo were among the artists en- 

 gaged on the St James' altar ; and Cioni, Ghiberti, 

 Cenni, Verrocchio, and Pollaiuolo worked at that 

 of St John. Some of the greatest artists in Italy in 

 the 14th and 15th centuries practised to some extent 

 the goldsmith's art, including Lucca della Kobhia, 

 (iliilierti, Brunelleschi, Donatello, and Jacopp della 

 Quercia. In the 16th century Cellini's is the 

 greatest name, although well-authenticated works 

 by him in the precious metals are few in number. 

 There are some very artistic productions in pewter 

 by the French artist Francis Briot, who lived in 

 the 16th century. 



Bronze is a metal in which many fine works have 

 lieen executed, and these are often of large size. 

 Few early examples exist of which the artists are 

 known. Stanracius of Constantinople cast in the 

 llth century the bronze gates of St Paul's- without- 

 the- Walls at Rome, destroyed in 1823, but of which 

 drawings exist. A century later an artist named 

 Barisanus made the fine bronze door of the cathe- 

 dral of Monreale in Sicily. One of the most 

 artistic productions in this metal of the 13th century 

 is the candelabrum in Milan Cathedral, 15 feet 

 high. The east door of the Baptistery at Florence, 



