YEA 



'YEA 



. fGie 

 ;2 Blu 



the latter disoxidised; and greenness is 

 considered as a state of equilibrium be- 

 tween the two series. De Candolle called 

 the first series xanthic (fav6>69, yellow), 

 and the second cyanic {Kvavo^, blue). The 

 two series may be thus expressed: — 

 Green. 



r Greenish-blue 

 I Blue 



I Violet-blue 

 ^ Violet 

 1. Violet-red 



Red. 



XANTHIC ACID {^avOo^, yellow). 

 An acid composed of sulphur, carbon, 

 hydrogen, and oxygen, and named from 

 the yellow colour of its compounds. 



XANTHIC OXIDE (^ave6<!, yellow). 

 A species of calculus, named from the 

 lemon-coloured compound which it forms 

 by the action of nitric acid. 



XANTHITE. A congeries of yellow 

 grains, no larger than those of sand, 

 easily separable from one another; found 

 in a limestone bed at Amity in the United 

 States. 



XA'NTHOGEN {^avOo^y yellow, yev- 

 vao), to produce). A terra applied to a 

 compound of sulphur and carbon, form- 

 ing the radical of hydroxanthic acid, 

 from its property of forming yellow com- 

 pounds with certain metals. 



XA'NTHOPHYLL (fav^of, yellow, 

 <pv\\ov, a leaf), Anthoxantine. The 

 yellow colouring matter which appears in 

 the leaves of plants in autumn. See 

 Chlorophyll. 



XANTHOPROTEIC ACID. An 

 orange-yellow powder, formed when al- 

 bumen, or any other protein-compound 

 is digested in nitric acid. 



XA'NTHOUSdai/^o?, yellow). A term 

 applied by Dr. Prichard to one of the 



three varieties of mankind, derived from 

 the colour of the hair, and including all 

 individuals or races which have brown, 

 auburn, yellow, flaxen, or red hair. 



Xl'PHIAS DORA'DO. The Sword 

 Fish ; a modern southern constellation, 

 consisting of seven stars. 



XIPHOSU'RA (f/0of, a sword, olpa, a 

 tail). A division of the entomostracous 

 crustaceans, in which the last segment of 

 the body forms a long, three-edged, sharp- 

 pointed weapon, as in the limulus or 

 Molucca crab. 



XI'PHYRRHYNCHS ($/0or, a sword, 

 pirfxoi, a beak). The designation of a 

 family of acanthopterygious fishes, of 

 which the xiphias, or sword-fish, is the 

 type. 



XY'LITE (fwXov, wood). Lignone. A 

 liquid existing in commercial pyroxylic 

 spirit. There are several other products 

 of the distillation of wood, named xylitic 

 acid, xylite-resin, xylite-naphtha, xy lite- 

 oil, &c. 



XYLO'DIUM. A term applied by 

 Desvaux to the nut of Anacardium. 

 This fruit is, however, generally referred 

 to the acheenium of other writers. 



XYLOIDINE. The name given to 

 paper which has been immersed for a 

 moment in strong nitric acid, and then 

 washed in distilled water. The paper 

 acquires the toughness of parchment and 

 the combustibility of tinder. 



XYLO'PHAGI {$u\ov, wood, <l>dya>, to 

 eat). Wood-eaters ; a family of the tetra- 

 merous Coleoptera, which usually live on 

 wood, which their larvae penetrate in 

 every direction. By the term xylotroges 

 {Tpwyw, to gnaw) is denoted a tribe of 

 serricorn beetles, which perforate timber ; 

 and by that of xylophilans (<piXea), to love) 

 a tribe of beetles which live on decayed 

 wood. 



YA'NOLITE. A designation of the 

 axinite of Haiiy, and thumerstone of 

 Kirwan ; an alumino-silicate of lime and 

 iron. 



YEAR. The period of time in which 

 the earth performs her revolution round 

 the sun, or that in which the sun appa- 

 rently moves from a point in the ecliptic 

 until he returns to the same point, is 

 called the solar year. This is also termed 

 the tropical year, and it consists of 365d. 

 380 



5h. 48m. 49s. 7. This is the period 

 adopted as the standard for the measure- 

 ment of time, for all the purposes of civil 

 life; hence, it is also called the civil 

 year. 



1. The sidereal year is measured from 

 the departure of the sun from any fixed 

 star to his return to the same star ; it is 

 longer than the tropical year, consisting 

 of 365d. 6h. 9m. 9s. 6, reckoned in mean 

 solar time, or 366d. 6h. 9m. 9s. 6 reckoned 



