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[297 ] 



MIT 



connection with the texture or 

 cleavage of a mineral was pointed 

 out, and, even then, it required 

 numerous and striking instances 

 of the critical discernment of Baiiy, 

 and other eminent mineralogists, in 

 predicting from the measurements 

 of the angles of crystals which had 

 heen confounded together, that 

 differences would be found to exist 

 in their chemical composition, all 

 which proved fully justified in their 

 result before the essential value of 

 this character was acknowledged. 

 The invention of the goniometer 

 by Carangeau, and subsequently 

 the reflecting goniometer by Dr. 

 "Wollaston, which last has been 

 improved by Sang, gave a fresh 

 impulse to that view of mineral- 

 ogy which makes the crystalline 

 form the essential or leading char- 

 acter, by putting it in the power of 

 every one, by the examination of 

 even the smallest portions of a 

 broken crystal, to ascertain the 

 character on which the identity of 

 a mineral in the system of Hauy 

 was made to depend. Mineralogy, 

 however, as a branch of natural 

 history, remains still distinct from 

 either optics or crystallography. 

 But whatever progress may have 

 hitherto been made in mineralogical 

 pursuits, every new advance has 

 opened a wider and more interesting 

 prospect. Mineralogy is in reality 

 essential to the geologist; it is 

 the very alphabet to the older 

 rocks, and it is probably to be at- 

 tributed in great measure to the 

 want of due preparation for the 

 study of these rocks, by an intimate 

 acquaintance with minerals in the 

 simple state, that the primary and 

 transition tracts have been investi- 

 gated in a far less degree than 

 those of a newer origin. The 

 science is still in its infancy, 

 and in many of its paths can 

 proceed only with a faultering 

 and uncertain step. Herschell. 



Jameson. Cleaveland. Phillips. 



MI'NITJM:. (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 yiietW, less, and 



MEI'OCENE. j KCLIVOS, recent, Gr.) 

 The name given by Sir C. Lyell to 

 a subdivision of the tertiary strata. 

 He says, " the European tertiary 

 strata may be referred to four suc- 

 cessive periods, each characterized 

 by containing a very different pro- 

 portion of fossil shells of recent 

 species." These four periods he 

 names, Newer Pliocene, Older Plio- 

 cene, Miocene, and Eocene. The 

 Miocene period has been found to 

 yield from eighteen to twenty-five 

 per cent, of recent fossils. This 

 was the result of an examination 

 of 1021 fossil species by M. De- 

 shayes. Many shells belong ex- 

 clusively to the Miocene period. 

 The Miocene strata are largely 

 developed in Touraine, and in the 

 South of France near Bordeaux, in. 

 the basin of Vienna, and other 

 localities. The miocene strata con- 

 tains 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. In regard to the 

 relative position of the strata, they 

 underlie the older Pliocene, and 

 overlie the Eocene formations, 

 when any of these are present. 



MI'TRA. A genus of shells belonging 

 to the Columellaria in Lamarck's 

 arrangement. It is a subfusiform 

 univalve, with a long, pointed, tur- 

 retted apex, a notched base, and 

 no canal. Covered with an epi- 

 dermis of a light brown colour. 

 The columella is plicated ; the 

 inferior plicee being the smallest. 



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