A R G 



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A R S 



a lamellated, or slaty structure ; a nearly 

 pure sub-species of carbonate of lime. 



A'RGIL. ") (argrilla, Lat. apyiXXog, or ap- 



A'RGILL. $ yiXo, Gr. argille, Fr. argilla, 

 It.) In 1754, Margraff showed that the 

 basis of alum is an earth of a peculiar 

 nature different from every other ; an 

 earth which is an essential ingredient in 

 clays, and gives them their peculiar pro- 

 perties. Hence this earth was called 

 argill ; Morveau afterwards gave it the 

 name of alumina, because it is obtained 

 in the state of greatest purity from 

 alum. 



ARGI'LLA. A genus of argillaceous earths. 



ARGILLA'CEOUS. (argillaceous, Latin.) 

 Clayey ; of the nature of argil ; contain- 

 ing argil. 



ARGILLACEOUS- SCHIST. Clay slate. An 

 indurated clay, or shale, common to the 

 fossiliferous and metamorphic series. 



ARGILLIFEROUS, (from argilla andfero, 

 Lat.) Producing or yielding clay. 



A'RGILLITE. Argillaceous-schist, or clay- 

 slate. Slate is a very extensive forma- 

 tion, composing entire mountains in 

 many alpine districts. The prevailing 

 colours are bluish, or greenish grey : it 

 has a silky lustre. 



ARGILLI'TIC. Containing argillite ; of the 

 quality of argillite ; resembling argillite. 



ARGI'LLOUS. (argillosus, Lat. argilleux, 

 Fr. argilloso, It.) Containing clay; of 

 the nature or quality of clay. 



ARGONA'UTA. The Paper Sailor ; a genus 

 of animals ; class Vermes, order Tes- 

 tacea. There are several species, but the 

 most remarkable one is the Argonauta 

 Argo, or Paper Nautilus. " Doubts still 

 exist whether the Sepia found within this 

 shell be really the constructor of it, or a 

 parasitic intruder into a shell formed by 

 some other animal not yet discovered. 

 Broderip, Gray, and Sowerby, are of 

 opinion, that this shell is constructed by 

 an animal allied to Carinaria." Buck- 

 land. 



Cuvier placed argonauta among the 

 subgenera of Sepia, and Dr. M'Murtrie, 

 in his translation, says, " These mol- 

 lusca are always found in a very thin 

 shell, symmetrically fluted and spirally 

 convoluted, the last whorl so large that it 

 bears some resemblance to a galley of 

 which the spine is the poop. The ani- 

 mal makes a consequent use of it, and in 

 calm weather whole fleets of them may 

 be observed navigating the surface of the 

 ocean, employing six of their tentacula 

 as oars, and elevating the two mem- 

 branous ones by way of a sail. If the sea 

 become rough, or they perceive any dan- 

 ger, the argonaut withdraws all its arms, 

 concentrates itself in its shell, and de- 

 scends to the bottom." 



A'RID. (aridus, Lat. aride, Fr. arido, It.) 

 Dry ; parched up ; devoid of moisture. 



ARI'DITV. ) ariditas, Lat. ariditt, Fr. 



A'RIDNESS. ] ariditcl, It.) Dryness ; the 

 state of being without moisture. 



ARMADI'LLO. (armadille, Fr.) The Dasy- 

 pus of Linnseus, and placed by him in 

 the order Bradypoda, class Mammalia. 

 Cuvier has placed the armadillo in the 

 order Edentata, or quadrupeds having no 

 front teeth, class Mammalia. The arma- 

 dillo is constructed with unusual adapta- 

 tions to the habit of burrowing in search 

 of its food, and shelter in the sand ; its 

 fore feet forming instruments of peculiar 

 power for the purpose of digging; and 

 presenting an extraordinary enlargement 

 and elongation of the extreme bones of 

 the toes, for the support of long and 

 massive claws. The armadillo and chlamy- 

 phorus are the only known animals that 

 have a compact coat of plated armour. 

 There are several subgenera. 



ARI'LLUS. ) (arillus, Lat.) A substance 



A'RIL. ) enclosing the seed in some 

 plants : it is either a complete or 

 partial covering of a seed, fixed to its 

 base only, and more or less loosely or 

 closely enveloping its other parts. Mace 

 is the arillus of the nutmeg: the red aril- 

 lus of the seed of the common spindle- 

 tree is well known, and is very ornamen- 

 tal in our hedges in the autumn. 



A'RMATURE. (armatura. Lat. armature, 

 Fr.) 



1. That by which the body is protected 

 from injury. 



2. Weapons of attack. 



ARME'NIAN STONE. A blue mineral, or 

 earth, variously spotted. It much re- 

 sembles Lapis lazuli. 



ARRA'GONITE. A variety of carbonate of 

 lime, found originally in Arragon, in 

 Spain, from which circumstance it has 

 obtained its name. Its colours are white, 

 grey, green, and blue ; it is found both 

 crystallized and massive. It is fre- 

 quently combined with a small propor- 

 tion, about four per cent, of carbonate of 

 strontites. 



ARSE'NIATE. A compound of arsenical 

 acid with a metallic oxide ; many arse- 

 niates are found native ; when heated 

 along with charcoal powder, they are de- 

 composed, and arsenic sublimes. 



A'RSENIC. (apfftvticbv, Gr. arsenic, Fr. 

 arsenico, It.) Native arsenic is a mineral 

 found in Germany, France, and England. 

 It occurs generally in masses of various 

 shapes ; its colour is that of blue steel ; 

 it is brittle : its surface readily tarnishes 

 on exposure to the atmosphere. When 

 struck it gives a smell resembling garlic ; 

 before the blow-pipe it emits a white 

 smoke, burns with a bluish flame, gives a 



