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GIL 



GE'RMINATE. (germino, Lat. germcr, Fr. 

 germinare, It.) To sprout; to bud; to 

 shoot forth. 



GERMINA'TION. (germination, Fr. germi- 

 nazione, It. germinatio, Lat.) The act 

 of sprouting or shooting forth. 



GE'YSER. The name given to certain 

 boiling springs or fountains in Iceland. 

 The water of these geysers holds a consi- 

 derable proportion of silex in solution. 

 The following account of the geysers of 

 Iceland is extracted from Mr. Lyell's 

 Principles of Geology. ' These inter- 

 mittent hot springs occur in a district 

 situated in the south-western division of 

 Iceland, where nearly one hundred of 

 them are said to break out within a cir- 

 cle of two miles. They rise through a 

 thick current of lava which may, per- 

 haps, have flowed from Mount Hecla, the 

 summit of that volcano being seen from 

 the spot at a distance of more than thirty 

 miles. Few of the geysers play longer 

 than five or six minutes at a time, and the 

 intervals between their eruptions are, for 

 the most part, very irregular. The great 

 geyser rises out of a spacious basin at the 

 summit of a circular mound composed 

 of siliceous incrustations deposited from 

 the spray of its waters. The diameter of 

 this basin is fifty-six feet in one direction 

 by forty-six in another. In the centre 

 is a pipe seventy-eight feet in perpen- 

 dicular depth, and from eight to ten feet 

 in diameter, but gradually widening as it 

 rises into the basin. The circular basin 

 is sometimes empty, but is usually filled 

 with beautifully transparent water in a 

 state of ebullition. During the rise of the 

 boiling water in the pipe, especially when 

 the ebullition is most violent, and when 

 the water is thrown up in jets, subterra- 

 nean noises are heard, like the distant 

 firing of cannon, and the earth is slightly 

 shaken. The sound then increases, and 

 the motion becomes more violent, till at 

 length a column of water is thrown up, 

 with loud explosions, to the height of one 

 or two hundred feet. After playing for 

 a time like an artificial fountain, and 

 giving off clouds of vapour, the pipe or 

 tube is emptied, and a column of steam 

 rushing up with amazing force and a 

 thundering noise, terminates the erup- 

 tion. If stones are thrown into the cra- 

 ter, they are instantly ejected, and such 

 is the explosive force, that very hard 

 rocks are sometimes shivered by it into 

 small pieces. 



GI'BBOUS. (gibbus, Lat. gilbeaux, Fr. gib- 

 boso, It.) Bossed ; convex ; bunched. 

 In botany, applied to fleshy leaves having 

 one or both sides convex, arising from the 

 great abundance of pulp. 

 GI'BBSITE. A mineral of a dirty white j 



colour, found in America, and named 

 after Mr. Gibbs. 



GILL. The lung, or respiratory orgr.n of 

 the fish. The gills, or branchiae, lie in 

 openings on each side of the head ; their 

 form is semicircular ; they have a vast 

 number of fibrillse standing out on each 

 side of them like a fringe, and very much 

 resemble the vane of a feather. There 

 are, in most fishes, four gills on each side, 

 resting on an equal number of arched 

 portions of cartilage or bone, connected 

 with the os hyoides. In some cartila- 

 ginous fishes there are five gills on each 

 side ; in the lamprey there are seven. 

 The larger Crustacea have their branchiae 

 situated on the under side of their body, 

 not only in order to obtain protection 

 from the carapace, which is folded over 

 them, but also for the sake of being 

 attached to the haunches of the feet, 

 jaws, and thoracic feet, and thus partici- 

 pating in the movements of those organs. 

 They may be seen in the lobster and in 

 the crab, by raising the lower edge of the 

 carapace. 



In the greater number of mollusca 

 these important organs, although external 

 with respect to the viscera, are within the 

 shell, and are generally situated near its 

 outer margin. They are composed of 

 parallel filaments, arranged like the teeth 

 of a fine comb ; and an opening exists 

 in the mouth for admitting the water 

 which is to act upon them. These fila- 

 ments appear, in many instances, to have 

 the power of producing currents of water 

 in their vicinity by the action of minute 

 cilia, similar to those belonging to the 

 tentacula of many polypi, where the same 

 phenomenon is observable. In the Ace- 

 phala, or bivalve mollusca, the gills are 

 spread out, in the form of laminae, round 

 the margin of the shell, as is exemplified 

 in the oyster when it is commonly known 

 by the name of beard. The aerated 

 water is admitted through a fissure in the 

 mouth, and when it has performed its 

 office in respiration, is usually expelled 

 by a separate opening. 



All the sepise have their gills enclosed 

 in two lateral cavities, which communi- 

 cate with a funnel-shaped opening in the 

 middle of- the neck, alternately receiving 

 and expelling the water by the muscular 

 action of its sides. The forms assumed 

 by the respiratory organs in this class are 

 almost infinitely diversified. In fishes 

 the gills form large organs, and the con- 

 tinuance of their action is more essential 

 to life than it appears to be in any of the 

 inferior classes. When their surfaces 

 are minutely examined, they are found to 

 be covered with innumerable minute pro- 

 cesses, crowded together like the pile of 



