MET 



[ 289 



MET 



are deemed relatively and compara- 

 tively as new metals. Iron is of 

 all ages. The specific gravity of 

 metals, if we exclude those recently 

 discovered by Sir H.Davy, is always 

 greater than that of minerals ; tellu- 

 rium, the lightest metal, being above 

 6'0, while the heaviest earthy body 

 is less than 5'0. Metals are opaque; 

 they possess a peculiar lustre, which 

 has been termed metallic lustre, 

 retaining it even when reduced to 

 powder. They are mostly malle- 

 able, or capable of being hammered 

 into various orders and thin leaves ; 

 and ductile, or capable of being 

 drawn into wires of greater or less 

 fineness. They are not soluble in 

 water. They all unite with oxygen, 

 and, probably, all with chlorine. 

 They are fusible, or capable of being 

 rendered fluid by a heat attainable 

 by artificial means ; becoming again 

 solid on cooling. They are elastic, 

 hard, heavy, and, generally, sono- 

 rous. Some of the metals possess a 

 degree of taste and smell. All the 

 metals are expansible by heat, and 

 their degree of expansibility appears 

 to bear a relation to their fusibility. 

 Two or three of the metals occur 

 in small quantities in the masses of 

 some of the earlier rocks, but in 

 general the metals are found in 

 veins ; some in veins traversing the 

 older rocks, and rarely or never in 

 those of a more recent description ; 

 others most abundantly, or only in 

 those of newer formation. 



METALLIC LTJ'STRE. One of the most 

 conspicuous properties of metals is 

 a particular brilliancy which they 

 possess, and which has been called 

 the metallic lustre. There are other 

 bodies which apparently possess this 

 peculiar lustre, as, for example, 

 mica, but in them it is confined to 

 the surface, and accordingly dis- 

 appears when they are scratched, 

 whereas it pervades every part of 

 metals. 



META'LLIC QBE. Metals existing in 



the state of an oxide, or a salt, 

 or united with a combustible, are 

 called ores ; and this term is, by 

 analogy, extended to the native 

 metals and alloys. They appear to 

 be the production of every period, 

 but more frequently exist in pri- 

 mary and transition, than in secon- 

 dary rocks, or than in alluvial 

 earths. 



META'LLIC O'XIDE. A metal combined 

 with any proportion of oxygen, is 

 called a metallic oxide, provided it 

 does not possess the properties of an 

 acid. 



META'LLIC SALTS. Those salts which 

 have a metallic oxide for their base; 

 carbonate of lead is an example. 



METALLIC VEINS. "Perhaps," says 

 Mr. Bake well, " the reader may 

 obtain a clearer notion of a metallic 

 vein, by first imagining a crack or 

 fissure in the earth, a foot or more 

 in width, and extending east and 

 west on the surface, many hundred 

 yards. Suppose the crack, or fis- 

 sure, to descend to an unknown 

 depth, not in a perpendicular direc- 

 tion, but sloping a little to the 

 north or south. Now, let us sup- 

 pose each side of the fissure to 

 become coated with mineral matter, 

 of a different kind from the rocks 

 in which the fissure is made, and 

 then the whole fissure to be filled 

 by successive layers of various 

 metallic and mineral substances ; 

 we shall thus have a type of a 

 metallic vein. Its course from 

 east to west is called its direction, 

 and the dip from the perpendicular 

 line of descent, is called its hading" 

 " There is a remarkable circum- 

 stance," says Prof. Phillips, " in 

 the distribution of metallic veins 

 in the same class of stratified rocks, 

 a peculiarity depending on local 

 influences; such, that while the 

 slates of Cornwall near the granitic 

 eruptions, yield tin and copper, and 

 the Snowdonian slates, and those 

 of Coniston Water Head yield 



