GAS 



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G E O 



round it, varying in number from two to 

 six ; sometimes they are wanting alto- 

 gether. The eyes are very small, and 

 sometimes wanting. Several are entirely 

 naked ; others have merely a concealed 

 shell, but most of them are furnished 

 with one that is large enough to receive 

 and shelter them. Most of the aquatic 

 gasteropoda, with a spiral shell, have an 

 operculum, a part sometimes horny, some- 

 times calcareous, attached to the pos- 

 terior part of the foot, which closes the 

 shell when its occupant is withdrawn into 

 it and folded up. The Umax or slug is 

 an example of the class. Cuvier divides 

 this class of Mollusca into nine orders, 

 namely, 1. the Pulmonea ; 2. the Nudi- 

 branchiata ; 3. the Inferobranchiata ; 4. 

 the Tectibranchiata ; 5. the Heteropoda ; 

 6. the Pectinibranchiata ; 7. the Tubuli- 

 branchiatse ; 8. the Scutibranchiata ; 9. 

 the Cyclobranchiata. 



GA'STRIC. (from ya<rr?}|0, Gr. yastrique, 

 Fr. yastrico, It.) Belonging to the sto- 

 mach or belly. 



GAULT. See Gait. 



GA'VIAL. A subdivision of the genus 

 crocodile, characterized by the narrow, 

 elongated, almost cylindrical jaws, which 

 form an extremely lengthened muzzle. 

 Dr. Mantcll. 



The living species of the crocodile 

 family are twelve in number, namely, 

 one gavial, eight crocodiles, and three 

 alligators. Teeth of the fossil gavial 

 have been found in the Tilgate strata, 

 and one of these is figured in Dr. Man- 

 tell' s Geology of the South-east of Eng- 

 land, who observes, " it appears that the 

 strata of Tilgate Forest contain the re- 

 mains of at least two, if not four, species 

 of crocodiles: that one of these (that 

 with slender curved teeth) resembles the 

 gavial of Caen, and probably was about 

 twenty-five feet in length. 



GE'HLINITE. A mineral allied to Vesu- 

 vian, and named after Gehlin. Colours, 

 various shades of green and brown. 

 Authors are not yet agreed as to its con- 

 stituents, &c. 



GE'LATINE \(gelee, Fr. gelatina, It.) A 



GE'LATIN. concrete animal substance ; 

 the principle of jelly. If a piece of the 

 fresh skin of an animal, after every im- 

 purity is carefully separated, be put into 

 a quantity of cold water, and boiled for 

 some time, part of it will be dissolved. 

 Let the decoction be slowly evaporated 

 till it is reduced to a small quantity, and 

 then put aside to cool. When cold, it 

 will have assumed a solid form, and pre- 

 cisely resemble that tremulous substance 

 known as jelly. This is, what is called 

 by chemists, gelatin. If the evaporation 

 be carried farther, the substance becomes 



hard, semitransparent, breaks with a 

 glassy fracture, and is, in short, that 

 substance known under the name of glue. 

 Gelatine therefore is the same with glue, 

 only that it is free from those impurities 

 with which glue is so often contaminated. 

 Gelatine is colourless and transparent; 

 when thrown into water it soon swells, 

 and assumes a gelatinous appearance, and 

 gradually dissolves away. By evaporat- 

 ing the water it may again be obtained 

 unaltered in the form of jelly. Cold 

 water dissolves it slowly, but water at a 

 temperature of 90 rapidly. Gelatin is 

 insoluble in alcohol. 



GELA'TINOUS. (gelatineux, -euse, Fr. qui 

 resemble a de la gelee.) Of the nature 

 of gelatine ; containing gelatine ; jelly- 

 like ; viscous. 



GELA'TINATE. To assume the appearance 

 of jelly. 



GELATINA'TION. The process of being 

 converted into a jelly-like substance. 



GEM. (gemma, Lat.) 



1. In mineralogy, any precious stone. 

 Gems may be divided into natural and 

 artificial ; the latter are made of what is 

 termed paste, coloured with different me- 

 tallic oxides. 



2. In botany, the bud, a small conoid 

 body, covered with scales, formed during 

 summer on the branches of trees, con- 

 taining the rudiments of a future plant, 

 or part of a plant : some plants produce 

 flowers and leaves, others leaves only, and 

 some flowers only. 



GEMELLI'PAROUS. (from gemelli and pario, 



Lat. ) Producing twins. 

 GE'MTNATED. In conchology, marked with 



a double elevated striae connecting the 



wreaths. 

 GE'MINOUS. (geminus, Lat.) Double ; 



in pairs. 



GE'MMULE. A little bud. 

 GE'NERA. The plural of genus. 

 GENE'RIC. } (generique, Fr. generico, It.) 

 GENE'RICAL. $ That which comprehends 



the genus, or distinguishes from another 



genus ; but does not distinguish the spe- 

 cies. 

 GENE'RIC ALLY. With regard to the genus, 



though not to the species. 

 GENI'CULATE. > (geniculat us, Lat. ) Knot- 

 GENI'CULATED. $ ted ; jointed ; applied 



to culms bent like the knee ; also to 



peduncles bent at the joints. 

 GE'NUS. (Lat.) 



1. That which is predicated of many 

 things, as the material or common part 

 of their essence. 



2. A subdivision of any class or order of 

 natural beings, whether of the animal, 

 vegetable, or mineral kingdoms, all agree- 

 ing in certain common characters. 



GE'ODE. (yew^K, from yea, Gr.) A 



