MEN 



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M E R 



large cavities of the body : these 

 membranes, after lining the sides 

 of their respective cavities, are 

 reflected back upon the organs 

 which are enclosed in those cavities, 

 so as to furnish them with an ex- 

 ternal covering. Thus the bowels 

 are covered by the peritoneum, the 

 lungs by the pleur ; nevertheless, 

 . in consequence of these membranes 

 being reflected, the lungs and 

 bowels may be said to be external 

 to their investing membranes. 



ME'NACHINE. (from Menachan, a val- 

 ley in Cornwall.) The name given 

 to a metal, to which the name 

 titanium is now more generally 

 applied. The menachine of Gregor 

 and the titanium of Klaproth are 

 the same substance, and to Gregor 

 is owing the merit of the discovery. 



ME'NACHANITE. (from Menachan, or 

 Menaccan, in Cornwall.) An oxide 

 of titanium, or menachine, com- 

 bined with iron. It is of a greyish- 

 black colour, and occurs in small 

 grains resembling gunpowder, of 

 no determinate shape, and mixed 

 with a fine grey sand. Specific 

 gravity 4'4. Before the blow-pipe 

 it neither decrepitates nor melts. 

 According to the analysis of Klap- 

 roth, it consists of oxide of iron 

 51-00, oxide of titanium 42'45, 

 silica 3 '50, oxide of manganese 

 0-25. 



ME'NILITE. (from Menil-montant, 

 near Paris, where it is found.) The 

 Menilit of Werner ; Silex meni- 

 lite of Brongniart ; Quartz resinite 

 subluisant of Hau'y. A brown or 

 yellowish-grey tuberose variety of 

 uncleavable quartz. By some 

 authors this mineral is placed as a 

 variety of semi-opal. From its 

 only having been found at Menil- 

 montant, near Paris, and from the 

 resemblance of some of its darker 

 varieties to pitch, it is sometimes 

 called Pitch-Stone of Menil-mon- 

 tant. Hoffmann divided Menilite 

 into two subspecies, namely, Brown 



Menilite and Grey Menilite. Meni- 

 lite occurs in small irregular or 

 roundish masses, often tuberose, or 

 marked with little ridges on its 

 surface. It is translucent, often 

 only at its edges. Structure rather 

 slaty ; fracture conchoidal or splin- 

 tery. It scratches glass. Specific 

 gravity 2-18. Infusible before the 

 blow-pipe. Constituents, silica 

 85-5, alumine 1, lime 0-5, oxide of 

 iron 0'5, water and carbonaceous 

 matter 11. 



MENI'NGES. (from ^v^g, Gr., a 

 membrane.) A name given to the 

 membranes which cover the brain. 



MENI'SCUS. (from ytn/wWos, Gr. A 

 lens, one of whose surfaces is 

 convex and the other concave, and 

 in which the two surfaces meet if 

 continued. As the convexity 

 exceeds the concavity, a meniscus 

 may be regarded as a convex lens. 



MEPHI'TIC A'CID. Another name for 

 carbonic acid. 



MEPHI'TIC AIE. Another name for 

 nitrogen gas. 



MEECTJEY. (mercure, Fr. mercuric, It.) 

 One of the sixty simple or elemen- 

 tary bodies. This metal is of the 

 same colour as burnished silver; 

 when pure and fluid, it is still 

 opaque, and nearly silver-white, 

 with a strong lustre. Its specific 

 gravity is 13-56, or thirteen times 

 and a-half heavier than water, its 

 density being next to those of plat- 

 inum and gold. Mercury freezes at 

 a temperature of 39 or 40 below 

 the zero of Fahrenheit, that is, at 

 a temperature of 71 below the 

 freezing point of water ; under 

 common circumstances we always 

 find it fluid, and in this respect it 

 remarkably differs from all the 

 other metals. It has obtained its 

 name from its fluidity and colour. 

 The boiling point of mercury is 

 somewhere about 680, at which 

 temperature it is converted into 

 vapour of a highly expansive 

 power j this vapour may be again 



