MIN 



MIS 



when they admit light, but are not trans- 

 parent ; opaque, when they transmit no 

 light, even when reduced to a finely 

 laminated state. The lustre, or degree 

 in which the surface of minerals reflects 

 light, is various : it may be glimmering, 

 glassy, pearly, resmous, silky, metallic, 

 adamantine. 



5. The texture of minerals is regular 

 or irregular ; lamellar, when it presents 

 the appearance of thin plates ; fibrous, 

 when composed, as it were, of threads or 

 filaments ; radiating, when the fibres 

 converge towards a point. 



MINERAL CAOUTCHOUC. A va- 

 riety of bitumen, resembling caoutchouc 

 in elasticity and softness, and in remov- 

 ing pencil-marks. 



MINERAL CHARCOAL. A fibrous 

 variety of non-bituminous mineral coal. 



MINERAL GREEN. A hydrated sub- 

 carbonate of copper, used as a pigment. 



MINERAL YELLOW. Patent yellow. 

 A pigment consisting of chloride and 

 protoxide of lead. 



MINERALIZATION. The process of 

 converting a substance into a mineral. 

 A metal combined with oxygen, sulphur, 

 &c., loses its metallic properties, and 

 becomes mineralized. The latter bodies 

 are then termed mineralizers : thus, in 

 the native oxides, oxygen is called the 

 mineralizer ; in the ores of lead and 

 copper, sulphur is the mineralizer, &c. 



MINERA'LOGY. The science which 

 relates to the accurate description, and 

 natural classification of minerals. That 

 branch of the subject which relates to 

 the arrangement of the descriptive cha- 

 racters of minerals, for the purpose of 

 distinguishing them from one another, 

 is more properly an art. 



MI'NIMUM (superl. of parvus, small). 

 The least possible quantity or effect, as 

 opposed to maximum, or the greatest 

 possible. 



MI'NIUM. Red lead or vermilion ; an 

 oxide of lead, of an intensely red colour, 

 employed as a pigment. Native minium, 

 from Hessia, Siberia, &c., is probably 

 produced by the decomposition of galena. 



MINOR TERM. In Logic, the mewor 

 term of a categorical syllogism is the 

 subject of the conclusion. The minor 

 premiss is that which contains the minor 

 term. In hypothetical syllogisms, the 

 categorical premiss is called the minor. 



MINUTE. The sixtieth part of a de- 

 gree of a circle. Minutes are denoted by 

 one acute accent, thus (') ; the second, 

 or sixtieth part of a minute, by two such 

 221 



accents ("); and the third by three ('"). 

 See Hour. 



MI'OCENE (ue/wv, less, Kaii/of, recent). 

 A division of tertiary strata, intervening 

 between the Eocene and Pliocene forma- 

 tions; so called, because a minority of 

 its fossil shells are referable to living 

 species. 



MIRACH, or /3 ANDROMEDA. A 

 star of the second magnitude, in the 

 constellation Andromeda. 



MIRAGE. A meteorological phenome- 

 non, depending partly on the vapour of 

 the atmosphere, and partly on the inter- 

 mixture of strata of air of different tem- 

 peratures and densities. It assumes the 

 appearance of a sheet of water, often 

 exhibiting the reflected or inverted 

 images of distant objects. This unusual 

 refraction frequently occurs when there 

 intervenes between the spectator and the 

 objects an expanse of smooth water, as 

 on the Oldenburg coast of the North Sea, 

 where it is called Kimmung ; or as at the 

 Straits of Messina, where it is called 

 Fata Morgana. 



MIRROR {mirer, French, to look at). 

 Any polished body which is impervious 

 to the rays of light, and reflects them 

 equally, so as to exhibit the images of 

 objects placed before it. When formed 

 of metal, it is sometimes termed specu- 

 lum, the Latin term for a looking-glass. 



1. Plane Mirror. That which has a 

 plane surface, as the common looking- 

 glass. 



2. Concave Mirror. That which has a 

 hollow surface, which collects the rays 

 and reflects them to a focus in front of 

 the mirror, thereby enlarging the image 

 of the object. 



3. Convex Mirror. That which has a 

 convex surface, which disperses the rays, 

 and consequently diminishes the image 

 of the object. These concave and convex 

 surfaces are formed of different curves, 

 according to the purposes intended, and 

 may be spherical, parabolic, or elliptical. 

 Mirrors with mixed surfaces are either 

 cylindrical or conical. See Burning- 

 glass. 



MISPI'CKEL. Arsenical pyrites; an 

 arsenio-sulphuret, some varieties of 

 which, containing accidentally admixed 

 silver, constitute Werner's weiss-ertz. 



MIST. A meteorological phenomenon, 

 occasioned by the vapour of the atmo- 

 sphere becoming visible; and this is a 

 consequence of the temperature of the 

 air being reduced below that of the 

 vapour. 



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