GIN 



L 194] 



G L A 



pal reason why fishes cannot main- 

 tain life, when surrounded by air 

 instead of water, is that the bran- 

 chiae become dry, and lose the 

 power of acting when thus deprived 

 of their natural moisture. The 

 rectification of this error is due to 

 Mourens, who pointed out the true 

 cause." 



GI'NGLYMOID. (from wfavpos and 

 e$>os, Gr.) Resembling a hinge; 

 pertaining to that species of hinge- 

 like joint which admits of flexion 

 and extension. 



GI'BASOLE. (from ^yro, 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 remark- 

 able property of reflecting a red 

 colour when turned towards the 

 sun, or any bright light. From 

 this peculiar property it obtained 

 its name. Girasole is sometimes 

 strongly translucent, and the finest 

 specimens resemble translucid jelly. 



GLA'CIEB. (glacier, Fr. Amas de 

 montagnes de glace, qui se trouvent 

 en quelques endroits de la Suisse de la 

 Savoie ei du Dauphine, au sommet des 

 montagnes. J Great accumulations or 

 extensive fields of ice, common 

 in mountainous countries. The 

 presence of glaciers depends on the 

 accumulation of a large mass of 

 snow, subject to variations of 

 temperature sufficient partially to 

 thaw and then to reconsolidate the 

 mass in its downward course. They 

 have been compared, aptly enough, 

 to gigantic icicles. At Mont Blanc, 

 the glacier of Montanvert is said 

 to descend 1,200 feet below the 

 summit of the mountain. " I was 

 much struck," says Mr. Darwin, 

 " by observing the great difference 

 between the matter brought down 

 by torrents and by glaciers : in the 

 former case a spit of gravel is 

 formed, but in the latter a pile of 



boulders." Glaciers are instru- 

 ments of the degradation of land, 

 inasmuch as they drive before them 

 and transport such substances as 

 they may have power to move. In 

 front of glaciers there is generally 

 a pile of rubbish, composed of 

 pieces of rock, earth, and trees, 

 which they have forced forward, 

 known in Switzerland by the name 

 of moraine. If there be a line of 

 moraine some distance from the 

 front of the glacier, it is considered 

 that the glacier has retreated to 

 the amount of that distance ; but 

 if there be no other than that 

 which the glacier immediately 

 drives before it, it is considered to 

 be on the increase. 



GLA'CIAL DEPOSITS. These consist of 

 clays, sands, and gravels, sometimes 

 stratified, sometimes rudely piled 

 together, and containing great 

 blocks of rock. These deposits are 

 generally known as "drift," and 

 " erratic block groups." 



GLANCE, (giants, 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. Moly- 

 bdena-glance ; 6. Bismuth-glance; 

 7. Antimony-glance; 8. Melane- 

 glance. 



GLANCE-COAL, (glanzkohle, Germ.) A 

 variety of coal, known also as an- 

 thracite. This is the glanzkohle of 

 Werner, the glance-coal of Jameson, 

 the native mineral carbon of Kir- 

 wan, and the blind-coal of some 

 authors. There are several varie- 

 ties of the glance-coal, namely, con- 

 cJioidal glance-coal, or that having 

 a conchoidal fracture and splendent 

 lustre; slaty glance-coal, or that 

 with a slaty structure; columnar 

 glance-coal, and fibrous glance-coal. 

 This combustible, at first view, 

 strongly resembles coal, from which, 



