QTPST-WORT. 





nit 



Mmilt, transparent UK! foliated. 



Kaiiia-'rH (ippnu, baring a radiated structure. 



Soli* SfMir, or Fibroin Gypnim, with white and delicate fibres. 



Alaktutcr. or .Soir C/jpwMM, white or light, with a very fine grain. 



Ptatltr o/ Parit, when burnt and ground. 



uni in all it* varieties, is readily distinguished from all other 

 iiiinrntls. by it* softneiw, by iU becoming an opaque powder without 

 fining before the blow-pipe, and the absence of all effervescence or 

 gcUtiniaing with acids. 



Sulphate of Lime is a frequent constituent of the strata of the earth. 

 It is found in layers in the Magneaian Linn-stone, is abundant in the 

 Ix>nilon Clay, and is a prominent constituent of many tertiary deposits, 

 as that of Puns. It is constantly present in the river and spring waters 

 of ( i rent Britain. It is found in the Thames, in the springs of Bath and 

 Bristol, and in many others, Gypsum is worked at Paris, ground and 

 burned, hence called Plaster of Paris. When water is added to this 

 powder it becomes a paste, which subsequently hardens ; hence its 

 Yaried uses in the arts, whenever the object is to procure casts or 

 models in relief. Alabaster comes mostly from Costelino in Italy. 

 It is cut into rases, statues, and ornaments of various kinds. Ala- 

 baster is also found in the Mammoth cave in Kentucky, United States. 

 It occurs in singularly beautiful imitutinn of flowers, leaves, shrub- 

 beries, and vines. Massive Gypsum occurs abundantly in New \ '.. 

 accompanying the rocks which afford the brine springs. It is also 

 found in Ohio, Illinois, Virginia, Tennessee, Arkansas, and Nova 

 Scotia. It is abundant in many parts of Europe. 



An anhydrous sulphate of lime is found, which is called Anhydrite. 

 [AMirnmTK.] 



< lypmim is used as a manure. [MANURES, in ARTS AND Sc. Div.l 

 OTreY-WOBT. [Lvt-oirs.] 



(JYHACA'NTIIUS, a gmus of Fossil Placoid Fishes, from the 

 Mountain Limestone and Coal Strata. There are four British species. 

 OYR-FALCON. [KAI.CIINII..K.] 



GYKIXID.K, a family of Coleopterous Insects belonging to the 

 section fmlamrra, and the sub-section Jlydrodephaga, or ' 

 Beetles, and distinguished by the minute size of th<> antenna-, winch 

 are clubbed and shorter than the head, the second joint being dilated 

 into a kind of ear externally ; the two fore lego are long and advanced 

 in front like arms, but the four posterior legs are very short and 

 compressed, but broad, forming two pair of short strong oars. The 

 eyes are four in number, two being placed above and two below ; the 

 palpi are very small ; the thorax short and transverse ; and the elytra 

 oral, depressed, and obtuse at the extremity, leaving the tip of the 

 abdomen exposed. 



This family corresponds with the genus Qyrinat of Linnnni", and 

 unlike the Dytictdir to which they are nearly ullie.d, these insects are 

 distinguished by the metallic brilliancy of their covering ; living for 

 the most part on the surface of the water, they r, ,-, ive the impressions 

 of the light in a more direct manner than the /'///iVr'c/./, and are 

 accordingly ornamented with tints of a brassy or bronzed metallic 

 hue, which glitter in the sun in the greatest degree. The velocity 

 with which they execute their evolutions upon the surface of the 

 water is really surprising, and has obtained for them the name of 

 Tourniquet* by the French, and Whirlgigs and Waterflies by the 

 English. Sometime! indeed they remain stationary for a time, so 

 that it seems easy to secure them, but on the least motion they are 

 instantly alert, escaping with surprising agility and diving to the 

 liottom of the water. The situation of their eyes adds greatly to 

 their defmce, enabling them to see objects both above and below 

 them. In the 'Journal of a Naturalist' we find the following account 

 of their proceedings : " Water quiet, still water affords a place of 

 action to a Terr amusing little fellow (Gyrinui natnt^r), which about 

 the month of April, if the weather be tolerably mild, we see 

 gamboling upon the surface of the sheltered pool ; and erery school- 

 boy who has angled for minnows in the brook is well acquaint' 

 thin merry little swimmer in his shining black jacket Retiring in 

 the autumn, and reposing all the winter in the mud at the bottom of 

 the pond, it awakens in the spring, rise* to the surface, and commences 

 its summer sport*. They associate in small parties of ten or a dozen 

 near the bank, where some little projection forms a bay or renders 

 the water perfectly tranquil ; and here they will circle round each 

 other without contention, each in hi* sphere, and with no apparent 

 object from morning until night with great sprightliness and 

 lion, snd so lightly do they more on the fluid, as to form only some 

 faint and transient circles on it* surface. Very fond of society ; \M- 

 seldom see them alone, or if parted by accident they soon rejoin their 

 busy companions. One pool commonly affords space for the amuse- 

 ment of several parties, yet they do not unite or contend, but 

 perform their cheerful circling* in separate family associations. If 



we interfere with th. ir merriment they seem greatly alarmed, disperse 

 or <livc to the bottom, where their fears shortly subside, as we soon 

 again see our merry little friends gamboling as be for.. \Vh 

 dire t" i of the water in the manner above described, they 



carry with them a little bubble of air affixed to 



'""dies. Also they are sometimes to be found flying, their well- 

 formed wings permitting such an oncrati. m, while the hii;h p"li-h of 

 the body protects them from the action of the wnt-r." With the 

 exception of a few exotic species, the insects of this family are of a 

 small size, seldom exceeding a quarter of an inch in length; and the. 

 largest ones do not reach one inch. Some of the species are found 

 on the margins of the ocean. They emit when touched a disagree- 

 able scent, arising from a milky fluid which exudes from t' 

 parts of the body, and which is not readily dispelled. The structure 

 of the fore le.sra indicates their mode of life, serving as arms to 

 convey the food, which they find floating upon the surface 

 water, and which consists of small dead insects, 4c., to the i. 

 The number of species of this family does not exceed 50 or i;> 

 of these not more than eight or nine are found in thin count, 

 these the Gyrinua natator is the most common. It is of a brilliant 

 bronzy black colour, with the sides of the body and antenna) metallic ; 

 the margins of the elytra and legs reddish. The elytra are 

 with lines of impressed spots. About a quarter of an inch in length. 



GY ROC All PI'S, a genus of Plants containing few species, but these 

 few are widely distributed one being found in South America on the 

 mountains of New Granada and Caracas, a second on those of tlm 

 Coromandel coast, and two others in the tropical parts <> 

 Gyrocarptu has, in conformity to the opinion of Mr. Brown, been 

 considered as allied to and l.y .--nine it has been placed in /,; 

 Illume refers it to his new order of lUiycttn. Dr. I.ind!,y considers 

 it as belonging to O, . The (lowers are pul 



hermaphrodite; the perianth superior, 4- to S li 1 : 

 ! opposite to divisions of perianth; anthers 2c -lied, with th 

 opening by a valve from below upwards; drupe 1 -seeded, having 



d to it two long membranous wings, the prolong 

 divisions of the perianth The embryo is inverse; 



I the cotyledons twisted spirally. The America-! 

 the Asiatic species as to have been thought identical by Dr. Ko\ 

 The latter grows to be a largo tree with co 

 deciduous about the end of the rainy season ; after which the ' 

 make their appearance in the cold weather, but an; -hoi fly followed 

 by the new leaves. The wood of this tree is whitish-coloured aud 

 very light It is preferred whenever procurable for making the cata- 

 marans, or rafts, on which the natives come off to ships through the 

 heavy surf of the Madras coast 



GY'RODUS (yvpos, round, o&ofa, a tooth), a genus of Fossil Fishes 

 established by Agassiz. The mouth of these fishes was armed with 

 rows of round grinding teeth in the palate for the crushing o; 

 Cnulacea and fHii -s with bony scales. In very fine specimens five 

 rows, which were placed on the os vomer in the roof of the mouth, 

 ) in the stone, though no other part of the h' ad is preserved; 

 but generally the teeth are loose, and were in that 

 Jiufonitci by the old writers (Llwyd, &c.) on organic ; 

 land's ' Bridgewater Treatise.') The fishes of this genus belong to thu 

 Oolitic Strata. 



GYKui; UNITES (yTpoi, round, YUMO, angle). This name was given 

 by Lamarck to small fossil bodies found in fresh-water tertiary 

 (Isle of Wi-rht, near Paris, &c.), under the supp.i.-itioii that, they were 

 shells of Polythuliunous Cephalopoda. ('Animaux san 

 torn, vii.) Lamarck was aware that his opinion was contested, and 

 that some persons imagined the small globular transversely carinated 

 Gyrogonitet were the seeds of an aquatic plant, but he "could not 

 believe it" It was however demonstrated in the 'Geological Trans- 

 actions' (vol. ii., second series), that they were in truth the fruits of 

 Chara, a genus of plants found in many fresh-water ponds. Tin 



ir-Uof this plant are v IUB, (lir. m ;:ni n i, // 



vi Yfydavx Fotsilrt, article 'Charactrc;' Lyell, 'Memoir,' in 



"riant, vol. ii., new series.) 



(lYIM'I.EHls, agenus of Fossil Ganoid Fishes, from theNewUed- 

 Sandstone Strata and bone-beds of the Lias. There are three I'.ri'i h 

 species. (Agassiz.) 

 GYRO'NCHUS, a genus of Fossil Ganoid Fishes, from the Oolite 



G YHOPIU'STIS, a genus of Fossil Placoid Fishes, from the Red- 



tie near Belfast (Agassiz.) 



c;Yl;<>STi:rs, a genus of Fossil Ganoid Fishes, from the Lias. 

 (Agassi*.) 



KM i OF VOLUME II. 



I.IMHUI I.I AMI I.VAM-, nUKll.HO, WIIITI.M.i . I . 



