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NA'CRB. (nacre, Fr. ndcchera, It.) 

 A sort of mother-of-pearl. The 

 fossil ink-bags of belemnites found 

 in the lias are surrounded by nacre. 



NA'CREOTJS. Glistening; silvery; ir- 

 ridescent. Having the appearance 

 of mother-of-pearl. Many mem- 

 braneous shells exhibit a nacreous 

 appearance on their internal surface, 

 as the Haliotis, or sea-ear ; Anodon, 

 or fresh-water muscle, &c. 



NA'CRITE. (from nacre.) A mineral 

 so called in consequence of its 

 pearly lustre. The Talcite of Kir- 

 wan. Nacrite occurs in reniform mas- 

 ses, composed of extremely minute 

 spangles, or glittering scales. Colour 

 pearly grey, with a tinge of red or 

 green. It fuses easily before the 

 blow-pipe. When rubbed between 

 the fingers it leaves a pearly gloss. 

 Unctuous to the touch. Its con- 

 stituents are, silex 56 '0, alumine 

 18-25, potash 8 -50, lime 3'10, iron 

 4-20, water 6-0. 



N'AGLE-FLTJE. The name given to a 

 conglomerate of great thickness, 

 occuring in Switzerland. 



NA'IAS. A genus of plants of the 

 order monandria, class dioscia, and 

 in the natural method ranking with 

 those of which the order is doubtful. 

 The male calyx is cylindrical and 

 bifid ; the corolla quadrifid ; there 

 is no filament, nor is there any 

 female calyx or corolla ; there is 

 one pistil ; the capsule is ovate and 

 unilocular. To this genus belong 

 the several species of zosterites, 

 found fossil in the cretaceous group. 



NA'KED. (nackt, Germ.) 



1. In botany, applied to flowers 

 having no calices ; to stems without 

 leaves; also to leaves when perfectly 

 smooth, and quite destitute of hairs. 



2. In zoology, applied to molluscs, 



when the body is not defended by a 

 calcareous shell. 



NA'PHTHA. (vatfrda, Gr. naptha, Lat. 

 naphte, Fr.) A variety of bitumen, 

 thin, volatile, fluid, and inflamma- 

 ble; unctuous to the touch, and 

 constantly emitting a strong odour. 

 Colours yellowish- white and yel- 

 lowish-grey; transparent. Specific 

 gravity from 0- 70 to 0-85. It is 

 highly combustible, igniting even 

 on the approach of a lighted taper. 

 It burns with a white or bluish 

 flame, produces a dense smoke, and 

 yields no residuum. It is insoluble 

 in alcohol. When long exposed to 

 the air, it becomes yellow and then 

 brown; its consistence is increas- 

 ed, and it passes into petroleum. 

 Naphtha consists of carbon 82 '2, 

 hydrogen 14-8. Springs of it exist 

 in many countries, particularly in 

 the neighbourhood of volcanoes. 

 The finest varieties of naptha are 

 found on the shores of the Caspian. 

 The soil is sandy and marly, and 

 the surrounding minerals are cal- 

 careous. The naptha is constantly 

 rising in the state of an odorous 

 inflammable vapour. The inhabi- 

 tants of the town of Baku, a port on 

 the shores of the Caspian sea, are 

 supplied with no other fuel than 

 that obtained from the naphtha and 

 petroleum with which the neigh- 

 bouring country is highly impreg- 

 nated. Mr. Coxe estimates the 

 produce of the naphtha springs at 

 Rangoon, Pegu, at 92,781 tons per 

 annum. Naphtha is burnt in lamps 

 instead of oil. 



NARC/ODES. The name assigned to a 

 genus of ichthyolites of the old red 

 sandstone. 



NA'RWAL. | (narwhal, narwatt, Germ. 



NA'KWHAX. ) the seauniorn.) The 



