Lubrication, introduction of a substance between the contact surfaces of moving parts to reduce friction and to dissipate heat. A lubricant may be oil, grease, graphite, or any substance—gas, ...

Carbon [Lat.,=charcoal], nonmetallic chemical element; symbol C; at. no. 6; at. wt. 12.011; m.p. about 3,550°C; graphite sublimes about 3,375°C; b.p. 4,827°C; sp. gr. 1.8–2.1 (amorphous), 1.9–...

Pencil, pointed implement used in writing or drawing to apply graphite or a similar colored solid to any surface, especially paper. From prehistoric times lumps of colored earth or chalk were ...

Zeya, river, c.800 mi (1,290 km) long, rising in the Stanovoy Range, Russian Far East, and flowing south to join the Amur River at Blagoveshchensk. It carries gold in its upper reaches, and it...

Ratnapura [Sinhalese,=city of gems], town (1995 est. pop. 46,000), SW Sri Lanka. Located in a rubber- and rice-producing area, Ratnapura is Sri Lanka's major precious-stone center, with ruby a...

Crucible, vessel in which a substance is heated to a high temperature, as for fusing or calcining. The necessary properties of a crucible are that it maintain its mechanical strength and rigid...

Bohemian Forest, Czech Český Les, Ger. Böhmerwald, mountain range, extending c.150 mi (240 km) along the S Czech-German border and extending into Austria. The Czech name for its southern secti...

Allotropy [Gr.,=other form]. A chemical element is said to exhibit allotropy when it occurs in two or more forms in the same physical state; the forms are called allotropes. Allotropes general...

Gneiss, coarse-grained, imperfectly foliated, or layered, metamorphic rock. Gneiss is characterized by alternating light and dark bands differing in mineral composition and having coarser grai...

Schist, metamorphic rock having a foliated, or plated, structure called schistosity in which the component flaky minerals are visible to the naked eye. Schists are distinguished from the other...