208 



ARNATTO 



ARENACEOUS. (Arena, sand.) Sandy. Kocks composed of particles of sand, 

 or containing much sand, as the grits and sandstones, are said to be arenaceous. If 

 they contain lime they are called arenaceo-calcareous. 



ARGAM 1 Oil.. An oil expressed from the kernels of the Argania Sideroxylon, a 

 shrub growing in Morocco. 



ARGILLACEOUS. Composed of clay, or clayey. This name is applied to all 

 rocks composed of clay. If containing also sand or lime, they are distinguished as 

 argillo-arenaceous or arffillo-calcareous. Argillaceous rocks, when breathed on, have a 

 peculiar earthy odour, by which they may be distinguished. 



.ARGILLACEOUS EABTH. (Argil la, clay, Lat.) The earth of clay, called 

 in chemistry, alumina, because it is obtained in greatest purity from alum. See 

 ALUMINA, CHINA CLAY, CLAY, KAOLIN. 



ARGOL, r ARGAL. (Tartre, Fr. ; Wetnstein, GOT.) The tartrate of potash 

 is known in commerce as the white and red argol ; the white being the crust let faD 

 by white wines, which is of a pale pinkish colour, and the red the crust deposited 

 from red wines, and of a dark red colour. See TABTAR, CBBAM OF TAB-TAB, &c. 



ARICINE. An alkaloid discovered by Pelletier and Corriol in a cinchona bark 

 from Arica in Peru. It is separated by the same process as quinine. 



ARMENIAN BOLE. See BOLE. 



ARMENIAN STONE. ARMENITE. A name formerly given to an earthy 

 copper ore mixed with limestone, of an azure colour, or to quartz coloured with car- 

 bonate of copper. See LAPIS LAZULI. 



ARMOUR-PLATES. Massive wrought-iron plates used for coating ships of 

 war. The iron for these plates should be as tough and soft as possible ; and steel, 

 though possessing high tensile strength, should not be used. It is an object of the 

 manufacturer to produce a plate of considerable thickness, as it is known that the 

 resistance of a single solid plate is greatly superior to that of a number of super- 

 imposed plates of the same aggregate thickness, however carefully the several plates 

 may have been fastened together. It is difficult, however, in manufacturing thick 

 plates, to completely squeeze out the liquid cinder interposed between the several 

 layers of iron which are welded together ; and hence armour-plates, when exposed to 

 the impact of heavy shot, often exhibit a tendency to lamination. The largo plates 

 are manufactured either by rolling in a mill or by forging under the steam-hammer : 

 it is said that the structure of a hammered plate is more likely to be uniform than 

 that of a rolled plate. ' The desideratum in all armour-plates is that they shall 

 bulge with the least possible amount of cracking. Large radiating fractures at the 

 back indicate brittleness, and should immediately condemn a plate.' (Percy.) 



ARNATTO, ARNOTTO, or ANNOTTO. (Rocou or roucou, Fr. ; Orleans, 

 Ger.) A somewhat dry and hard paste, brown without and red within. It is 

 usually imported in cakes of two or three pounds weight, wrapped up in leaves of 

 large reeds, packed in casks, from America, where it is prepared from the seeds of a 

 certain tree, called the arnatto tree ; it is the JBixa orettana of Linnaeus. 



The shrub producing the arnatto is originally a native of South America ; it is 



