G L A 



G L A 



however, it materially differs. Its 

 colour is black, or rather grayish 

 and iron-black, sometimes tinged 

 with blue or brown. It, perhaps, 

 never possesses the pure deep black 

 of coal. Glance-coal, like the dia- 

 mond, appears to be essentially 

 composed of pure carbon, but in a 

 very different state of aggregation. 

 The glance-coal of Kilkenny con- 

 tains about 97 per cent, of carbon ; 

 that of Rhode Island about 94 or 

 95. It occurs in beds in the coal 

 formation, in the secondary class of 

 rocks; it is occasionally found 

 among rocks of the primary and 

 transition series. It is sometimes 

 nearly allied to graphite. It may 

 be distinguished from coal by the 

 difficulty with which it burns, by 

 its greater specific gravity, and by 

 its composition : it differs from 

 graphite in being less heavy; its 

 trace on paper is dull and blackish, 

 whereas that of graphite is a shin- 

 ing metallic gray ; and graphite is 

 unctuous to the feel, whereas 

 glance-coal is not. 

 GLAND, (glande, Fr. glandula, It.) 

 1 . Bodies employed to form or alter 

 the different liquids in the animal 

 body. There are two distinct sets 

 of glands, the conglobate, and the 

 conglomerate. Great variety is 

 observable both in the form and 

 structure of different glands, and in 

 the mode in which their blood- 

 vessels are distributed. In some 

 glands, the minute arteries suddenly 

 divide into a great number of 

 smaller branches, like the fibres of 

 a camel-hair pencil ; this is called 

 the pencillated structure. Some- 

 times, the minute branches, instead 

 of proceeding parallel to each other, 

 after their division, separate like 

 rays from a centre, presenting a 

 stellated arrangement. In the 

 greater number of instances, the 

 smaller arteries take a tortuous 

 course, and are sometimes coiled 

 into spirals. It is only by means 



of microscopic aid that these 

 minute structures can be rendered 

 visible. 



2. In botany, a small transparent 

 tumour or vesicle, discharging a 

 fluid, either oily or watery, and 

 situated on various parts of plants, 

 as the stalk, calyx, leaves, &c. 

 These glands are composed of 

 closely compacted cells, which 

 perform the functions of secretion, 

 or the conversion of the nutritious 

 juices into particular products 

 required for various purposes in 

 the economy of the plant. The 

 perfume of the flowers and leaves 

 of plants arises from secretions from 

 glands. 



GLANDI'FEROUS. (from glandifer, Lat.) 

 Bearing acorns, or fruit resembling 

 acorns. 



GLA/NDULAH. } (glanduleux, Fr. glan- 

 GLA/NDTTLOUS. ) duloso, It. glandu- 

 losits, Lat.) 



1. Pertaining to glands; contain- 

 ing glands ; full of glands. 



2. In botany, applied to the 

 margins of leaves having glands. 



GLA/NDULOFS GNEISS. A variety of 

 gneiss, (in which the mica is some- 

 times arranged in undulated layers,) 

 presenting numerous small masses 

 of felspar or quartz, of a globular 

 or ellipitical form, interspersed like 

 glands through the mass. From 

 this circumstance it has obtained 

 its name. 



GLASSY PUMICE. The Glasiger Bim- 

 stein of Werner and Harsten. A 

 subspecies of pumice, for a de- 

 scription see Pumice. 



GLAU'BBEITE. An hydrous sulphate 

 of soda and lime. A mineral of a 

 white or yellow colour; crystal- 

 lised in oblique four-sided prisms ; 

 consisting of 51 parts sulphate of 

 soda, and 49 parts sulphate of 

 lime. It is less hard than carbo- 

 nate of lime, but scratches sulphate 

 of lime. It is found in New 

 Castile, in Spain, disseminated in 

 muriate of soda. 



