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velvet ; and on these are distributed 

 myriads of blood-vessels, spread like a 

 delicate net work, over every part of their 

 surface. A large flap, termed the oper- 

 culum, extends over the whole organ, 

 defending it from injury, and leaving 

 below a wide fissure for the escape of the 

 water which has performed its office in 

 respiration. For this purpose the water 

 is taken in by the rnouth, and forced by 

 the muscles of the throat through the 

 apertures which lead to the branchial 

 cavities ; in this action the branchial 

 arteries are brought forward and sepa- 

 rated to a certain distance from each 

 other, and the rush of water through 

 them unfolds, and separates, each of the 

 thousand minute filaments of the bran- 

 chioe, so that they all receive the full 

 action of that fluid as it passes by them. 

 When a fish is taken out of the water, the 

 animal vainly reiterates its utmost efforts 

 to raise the branchiae, and relieve the sense 

 of suffocation it experiences in conse- 

 quence of the general collapse of the fila- 

 ments of those organs, which adhere 

 together in a mass, and can no longer 

 receive the vivifying influence of oxygen. 

 " It has been generally stated," says Dr. 

 Roget, "by physiologists, even of the 

 highest authority, that the principal rea- 

 son why fishes cannot maintain life, when 

 surrounded by air instead of water, is 

 that the branchiee become dry, and lose 

 the power of acting when thus deprived 

 of their natural moisture. The rectifica- 

 tion of this error is due to Flourens, who 

 pointed out the true cause." 



GI'NGLYMOID. (from ytyyXv/zos and tldoQ, 

 Gr.) Resembling a hinge ; pertaining 

 to that species of hinge-like joint which 

 admits of flexion and extension. 



GI'NGLYMUS. (ytyyX^juof, Gr.) Articu- 

 lation admitting flexion and extension. 



GI'RASOLE. (from gyro, to turn, and sol, 

 the sun, Lat.) The name given to a 

 variety of opal. The silex girasol of 

 Brongniart, and quartz resinite girasol of 

 Haiiy. The girasole is of a milk white 

 colour, but it possesses a remarkable 

 property of reflecting a red colour 

 when turned towards the sun, or any 

 bright light. From this peculiar property 

 it obtains its name. Girasole is some- 

 times strongly translucent, and the finest 

 specimens resemble translucid jelly. 



GLA'BROUS. (glaber, Lat.) Smooth ; the 

 opposite to hairy ; downy. 



GLA'CIAL. (glacialis, Lat. glacial, Fr.) 

 Icy ; frozen. 



GLA'CIER. (glacier, Fr. Amos de mon- 

 tagnes de glace, qui se trouvent en quel- 

 ques endroits de la Suisse de la Saroie et 

 du Dauphint, au sommet des montagnes.} 

 Great accumulations or extensive fields 



of ice, common in mountainous coun- 

 tries. 



GLA'CIS. (glacis, F.) A sloping bank. 



GLANCE, (glantz, Germ.) 



1 . A name given to some minerals which 

 possess a metallic, or pseudo-metallic 

 lustre. 



2. An order of minerals, containing eight 

 genera. 1. Copper glance ; 2. Silver- 

 glance ; 3. Lead-glance ; 4. Tellurium- 

 glance; 5. Molybdena-glance ; 6. Bis- 

 muth-glance ; 7. Antimony-glance ; 8. 

 Melane-glance. 



GLANCE -COAL, (glanzkohle, Germ.) A 

 variety of coal, known also as anthracite. 

 This is the glanzkohle of Werner,; the 

 glance-coal of Jameson, the native mine- 

 ral carbon of Kirwan, and the blind- 

 coal of some authors. There are several 

 varieties of the glance-coal, namely, con- 

 choidal glance-coal, or that having a 

 conchoidal fracture and splendent lustre ; 

 slaty glance-coal, or that with a slaty 

 structure ; columnar glance-coal, and 

 fibroifs glance-coal. This combustible, 

 at first view, strongly resembles coal, 

 from which, 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 diamond, appears to be 

 essentially composed of pure carbon, but 

 in a very different state of aggregation. 

 The glance-coal of Kilkenny contains 

 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 occasion- 

 ally found among rocks of the primary 

 and transition series. It is sometimes 

 nearly allied to graphite. It may be dis- 

 tinguished from coal by the difficulty 

 with which it burns, by its greater spe- 

 cific 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 shining 

 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 



