70 GLOSSARY. 



GRAMINEJE, the order of plants to which grasses belong. Etym., 

 gramen, grass. 



GRANITE. An unstratified or igneous rock, generally found inferior 

 to or associated with the oldest of the stratified rocks, and some- 

 times penetrating them in the form of dikes and veins. It is 

 composed of three simple minerals, felspar, quartz, and mica, 

 and derives its name from having a coarse granular structure ; 

 granum, Latin for grain. Westminster, Waterloo, and London 

 bridges, and the paving-stones in the carriage-way of the Lon- 

 don streets are good examples of the most common varieties of 

 granite. 



GRAUWACKE, a German name, generally adopted by geologists for 

 the lowest members of the secondary strata, consisting of sand- 

 stone and slate, and which form the chief part of what are 

 termed by some geologists the transition rocks. The rock is 

 very often of a grey colour, hence the name, grau being German 

 for grey, and wacke being a provincial miner's term. 



GREENS AND. Beds of sand, sandstone, limestone, belonging to the 

 Cretaceous Period. See Table II. F, p. 390. The name is 

 given to these beds, because they often, but not always, contain 

 an abundance of green earth or chlorite scattered through the 

 substance of the sandstone, limestone, &c. See vol. iii. p. 324. 



GREENSTONE, a variety of trap, composed of hornblende and felspar. 



GRIT, a provincial name for a coarse-grained sandstone. 



GYPSUM, a mineral composed of lime and sulphuric acid, hence 

 called also sulphate of lime. Plaster and stucco are obtained 

 by exposing gypsum to a strong heat. It is found so abun- 

 dantly near Paris, that Paris plaster is a common term in this 

 country for the white powder of which casts are made. The 

 term is used by Pliny for a stone used for the same purposes by 

 the ancients. The derivation of it is unknown. 



GYPSEOUS, of, or belonging to, gypsum. 



GYROGONITES. Bodies found in fresh-water deposits, originally sup- 

 posed to be microscopic shells, but subsequently discovered to 

 be the seed-vessel of fresh-water plants of the genus chara. See 

 vol. ii. p. 273, and 2d Edit. p. 280. Etym. yvpoc, gyros, curved, 

 and yoro, go7ios, seed, on account of their external structure. 



UEMIPTERA, an order of insects, so called from a peculiarity in their 

 wings, the superior being coriaceous at the base, and mem- 

 branous at the apex, ?//.ao-v, hcmisu, half, and Trrefov, ptcron, 

 wing. 



HORNBLENDE, a simple mineral of a dark green or black colour, 



