AKEOMETER 



207 



adding to tho decoction of archil a little salt of tin (muriate), and passing the cloth 

 through the bath after it has been prepared by a mordant of tin and tartar. It must 

 be afterwards passed through hot water. 



Dyeing with archil with the aid of oil has been patented by Mr. Lightfoot, on the 

 same principle as has been so long used in the Turkey-red cotton dye, who also has 

 recourse to metallic and earthy bases. See CUDBEAR and LITMUS. 



Under the names of archil carmine and archil purple, or French Purple, two bril- 

 liant dyes wore introduced about a dozen years ago ; these contained the colouring 

 principles of the lichens in a very pure form. But since the introduction of the brilliant 

 and stable colours derived from coal-tar, archil and the other dye-stuffs yielded by 

 lichens have greatly fallen into disuse. 



ARCHITECTURE. The art of constructing buildings, which involves tho con- 

 sideration of very dissimilar points. 



1. UTILITY, as it regards any specified object, as 



a. Domestic accommodation in a dwelling-house. 



b. Acoustic arrangements in all buildings intended for public purposes. This 



consideration is entirely lost sight of by many modern architects. 



c. Ventilation, which is a matter upon which a very large amount of empiri- 



cism has been expended with exceedingly small results. 



2. DURABILITY. If we examine the walls of our ruined abbeys and castles, we 

 shall find that the stones employed still retain the marks of the workman's tool ; and 

 that in numerous cases the ornamental work is as sharp as if it had been executed but 

 yesterday. This should prove to us that the selection of stone was of great importance. 



ARDENT SPIRITS called formerly Aqua ardens are the spirituous products 

 of a considerable variety of fermentable substances. The term is more strictly 

 applicable to those spirits which, by careful distillation, have been deprived of a 

 large quantity of tho water in combination. Rectified spirit is alcohol with 16 per cent, 

 of water. Proof spirit is 5 pints of rectified spirit with 3 pints of distilled water. 



ARECA. A genus of palms, containing two species 1. The Arcca catechu, pro- 

 ducing the betel nut, which is so universally chewed in tho East Indies. 2. The 

 Areca olcracea, or cabbage-palm ; the cabbage is eaten in the West Indies, both raw 

 and boiled; and the trunk, which is often 100 feet long, is used in Jamaica for water- 

 pipes, which are said to become, when buried, almost as hard as iron. 



A. catechu is one of the most beautiful palm-trees growing in India. It is chiefly 

 cultivated in Malabar, Ceylon, and Sumatra. One tree will produce, according to 

 situation, age, and culture, from 200 to 800 nuts. See ACACIA CATECHU. 



AREOMETER. An instrument to measure the densities of liquids. (See ALCO- 

 HOLOMETRY.) Tlio principle will be well understood by remembering that any solid 

 body will sink further in a light liquid than in a heavy one. The areometer is usually 

 a glass tube, having a small glass bulb loaded with either shot or quicksilver, so as to 

 set the tube upright in any fluid iu which it will swim. Within the tube is placed a 

 graduated scale : wo will suppose the tube placed in distilled water, and the line cut 

 by the surface of the fluid to be marked ; that it is then removed and placed in strong 

 alcohol the tube will sink much lower in this, and consequently we shall have two 

 extremities of an arbitrary scale, on which we can mark any intermediate degrees. 



The areometer of Baume is used in France, and the following scale is adopted by 

 the French chemists : 



Specific Gravity Numbers corresponding with Baume' s Areometrio Degrees. 



