M I N 



[ 169 ] 



M O L 



the character on which the identity of 

 mineral in the system of Haiiy was mad 

 to depend. Mineralogy, however, as a 

 branch of natural history, remains stil 

 distinct from either optics or crystallo- 

 graphy. But whatever progress may have 

 hitherto been made in mineralogica] 

 pursuits, every new advance has opened a 

 wider and more interesting prospect. 

 The science is still in its infancy, and in 

 many of its paths can proceed only with 

 a faultering and uncertain step. Hers- 

 chell. Jameson. Cleaveland. 



MI'NIUM. (minium, Lat.) A red oxide 

 of lead. Minium is of a bright scarlet ; 

 it occurs in a loose state, or in masses, 

 composed of flakes with a crystalline 

 texture. It is found in the lead mines of 

 Westphalia. It is used in glass-making, 

 enamelling, and some other arts. 



MI'OCENE. (from /mW, less, and Kaivbg, 

 recent, Gr.) The name given by Mr. 

 Lyell to a subdivision of the tertiary 

 strata. He says, the European tertiary 

 strata may be referred to four successive 

 periods, each characterized by containing 

 a very different proportion of fossil shells 

 of recent species. These four periods he 

 names, Newer Pliocene, Older Pliocene, 

 Miocene, and Eocene. The Miocene 

 period has been found to yield eighteen 

 per cent, of recent fossils. This was the 

 result of an examination of 1021 fossil 

 species by M. Deshayes. Many shells 

 belong exclusively to the Miocene period. 

 The Miocene strata are largely developed 

 in Touraine, and in the South of France 

 near Bourdeaux, in the basin of Vienna, 

 and other localities. The miocene strata 

 contain an admixture of the extinct genera 

 of lacustrine mammalia of the Eocene 

 series, with the earliest forms of genera 

 which exist at the present time. 



MI'TRA. A genus of shells belonging to 

 the Columellaria in Lamarck's arrange- 

 ment. It is a subfusiform univalve, with 

 a long pointed turreted apex, a notched 

 base, and no canal. Covered with an 

 epidermis of a light brown colour. The 

 columella is plicated ; the inferior plicae 

 being the smallest. Mitres are found 

 both fossil and recent. The recent are 

 found at depths varying to seventeen 

 fathoms, on reefs, in sands, and in sandy 

 mud. Of the fossil mitres, Lamarck de- 

 scribes thirteen species as having been 

 found in the neighbourhood of Paris. 



MO'CHA STONE, (from Mocha, in Arabia.) 

 The quartz agathe arborise of Haiiy. 

 Called also dendritic agate. A mineral, 

 containing in its interior very beautiful 

 delineations of leafless shrubs, trees, &c., 

 of a brown or dark colour. Mocha stones 

 resemble those agates which are found on 

 the Sussex coast called dendrachates. 



MODI'OLA. (from modiolm, Lat. a little 

 measure.) A genus of shells belonging 

 to the family Mytilacea. A transverse 

 inequilateral bivalve. Parkinson states 

 that modiolae do not attach themselves 

 by a byssus, but this is incorrect. The 

 modiola is a littoral shell, moored to 

 rocks, stones, and shells. One species, 

 modiola discors, floats free, enveloped in 

 its own silky byssus. One modiola lives 

 in the ascidias, and another floats among 

 the Gulf or Sargasso weed. The fossil 

 species have been found in the neigh- 

 bourhood of Paris, and some in this 

 country. 



MO'LAR (from mola, a mill, Lat. molaire, 

 Fr.) A grinder-tooth. The large double 

 teeth are called molar teeth, or grinders ; 

 these are, however, subdivided according 

 to their different forms ; thus those with 

 two fangs are called bicuspid, or false 

 molar teeth. The posterior molar teeth 

 are differently shaped in carnivorous ani- 

 mals, for they are raised into sharp, and 

 often serrated, edges, having many of the 

 properties of cutting teeth. In insecti- 

 vorous and frugivorous animals, their 

 surface presents prominent tubercles, 

 either pointed or round, for pounding the 

 food ; while in graminivorous quadrupeds 

 they are fiat and rough, for the purpose 

 simply of grinding. 



MOLA'SSE. (from mollis, soft, Lat.) The 

 name given to a soft green sandstone 

 found in Switzerland ; one of the most 

 recent of the tertiary deposites. Lyell. 

 In the Molasse of Switzerland there are 

 many deposites affording sometimes coal 

 of considerable purity. Prof. Buckland. 

 Mr. Bakewell observes, " By many 

 geologists it is maintained that the beds 

 of soft sandstone, called molasse, belong 

 to the London clay division of the ter- 

 tiary formations. That some of these 

 beds may be tertiary, I do not deny ; but 

 I am fully convinced, that many beds 

 called molasse, in Savoy, are covered by 

 the Jura limestone and oolites, having re- 

 peatedly seen them in contact, and got 

 specimens from each bed at the line of 

 junction." 



WO'LECULE. (molecule, Fr. petite partie 

 d'un corps.} A minute particle of a mass 

 or body, differing from atom, inasmuch as 

 it is always a portion of some aggregate. 

 All substances consist of an assemblage 

 of material particles, which are far too 

 small to be visible by any means human 

 ingenuity has yet been able to devise, 

 and which are much beyond the limits of 

 our perceptions. The size of the ulti- 

 mate particles of matter must be small in 

 the extreme. Organised beings, possess- 

 ing life and all its functions, have been 

 discovered so small that a million of them 



