240 MICA 



Copper, 100; gold, 93-6; silver, 73-6; zinc, 28'5 ; platinum, 16-4; iron, 15'8; tin, 

 15 - 5; lead, 8'3 ; mercury, 3'5 ; potassium, 1'33. 



The metals -which hardly, if at all, conduct electricity, are zirconium, aluminium, 

 tantalum, in powder, and tellurium. 



3. Metals are probably opaque ; yet gold-leaf, as observed by Newton, seems to 

 transmit the green rays, for objects placed behind it in the sunbeam appear green. 

 This phenomenon has, however, been ascribed to the rays of light passing through 

 an infinite number of minute fissures in the thinly-hammered gold. 



4. All metals are capable of combining -with oxygen, but with affinities and in 

 quantities extremely different. Potassium and sodium have the strongest affinity for 

 t ; gold and the platinum-group of metals the feeblest. Many metals become acids by a 

 sufficient dose of oxygen, while, with a smaller dose, they constitute salifiable bases. 



5. Metals combine with each other, forming a class of bodies called alloys, except 

 when one of them is mercury, in which case the compound is styled an amalgam. 



6. They combine with hydrogen into hydrurets or hydrides ; with carbon, into car- 

 burets or carbides ; with sulphur, into sulphurets or sulphides ; with phosphorus, into 

 phosphurets or phosphides ; with selenium, into scleniurets or selcnidcs with boron, 

 into borides ; with chlorine, into chlorides ; with iodine, into iodides ; with cyanogen, 

 into cyanides ; with silicon, into silicides ; and with fluorine, into fluorides. 



7. Metallic salts are definite compounds mostly crystalline of the metallic 

 oxides with the acids. 



METAIiS, NATIVE. The metals which are found in the condition of obvious 

 metallic existence are but few. Gold is almost always found native, generally com- 

 bined with a small percentage of silver, and sometimes with other rarer metals. 

 Silver is frequently discovered in an almost pure metallic state. Platinum is another 

 metal, which, like gold, is generally found in the metallic state, but this metal is almost 

 always combined with palladium, osmium, and other metals of that type. Copper 

 is very often found in the native state, and in a condition of great purity. The 

 occurrence of large masses of copper copper rocks, indeed is one of the most 

 striking features of the Lake Superior copper deposits. Lead is said to have been 

 found native at Grassington, in Yorkshire. Recently it is reported to have been 

 discovered in Victoria, Australia, and again in California. Bismuth is often found 

 native ; and Iron, the meteoric variety, is occasionally met with in this condition. 



1VXETAI<S, KTOBXiE. This term was applied to gold and silver in ages when the 

 principles of chemical science were unknown. The name was intended to convey 

 the fact that these metals were slow to combine with the ' baser ones," such as iron. 

 The term is not now employed scientifically. 



METEORITES. (Aerolithe, Fr.) The name of mineral bodies which have been 

 known to fall from the region beyond the earth's atmosphere to the surface of the 

 earth. There are, however, a certain number of bodies found on the surface in various 

 parts of the world, "which are thought to bo of meteoric origin, and are hence called 

 Meteorites, which correspond in chemical composition and structure with those which 

 have been seen to fall. They are usually divided into Meteoric Iron and Meteoric 

 Stones. The meteoritic irons have been termed Siderites, whilst the term Aerolites has 

 been retained for the stony meteorites. The following may be regarded as the average 

 composition of meteoric iron : Iron, 85'54 ; nickel, 8'55 ; cobalt, 1'50; copper, 0'20; 

 magnesia, 2 - 04; chromic oxide, 0'21 ; silica, 3'0 ; phosphorus, - 12 ; with traces of 

 carbon, sulphur, tin, and manganese. For numerous analyses, see Watts's ' Dictionary 

 of Chemistry.' See AEROLITES. 



!VIETHYI,AIVIIN-. CPH'N (CH 5 JU). The most volatile of the organic bases. 

 It is formed by similar reactions to ethylamine ; it is regarded as ammonia in which 

 an equivalent of hydrogen is replaced by methyle ; it is gaseous at ordinary tempera- 

 tures ; it is the most soluble in water of all known gases, one volume of water at 54 

 dissolving 1,150 volumes. 



METHYLATED SPIRIT. When ordinary alcohol is mixed with 10 per cent, 

 of 'wood alcohol' (Methyle), it is, according to an excise regulation, sold duty free 

 under this name. Methylated spirit is extensively used in the manufacture of var- 

 nishes, lacquers, &c. See Watts's ' Dictionary of Chemistry.' 



METHYXiEXE, a peculiar liquid compound of carbon and hydrogen, extracted 

 from pyroxilic spirit, which is reckoned to be a bi-hydrate of methylene. 

 METRIC SYSTEM. See WEIGHTS AND MEASURES. 



MICA is a finely-foliated mineral, of a pearly metallic lustre. It is harder than 

 gypsum, but not so hard as calc-spar ; flexible and elastic ; spec. grav. 2 - 6o. It is 

 an ingredient of granite and gneiss. The large sheets of mica exposed for sale in 

 London are mostly brought from Siberia. They are used, instead of glass, to enclose 

 the fire, without concealing the flame, in certain stoves. 



The mica of Fahlun, analysed by Eose, afforded silica, 46-22 ; alumina, 34'52 ; 



