MINERALOGY. 447 



medicine is well known as soda powders. According to 

 Herodotus soda was employed by the Egyptians in em- 

 balming. 



THIRD ORDER. 

 MELLITE OF ALUMINA. OXALATE OF LIME. 



Honey Stone Mellite is a crystal ; luster resinous, 

 inclining to vitreous. Streak white ; color, honey-yel- 

 low ; often reddish or brownish, semi-transparent. Frac- 

 ture conchoidal. Burns readily in heated air, leaving 

 an earthy deposit. When burnt in the open air, neither 

 smoke nor flame is observable, and it eventually acquires 

 the color and consistence of chalk. Was formerly classed 

 among the mineral resins as a kind of amber, which, nev- 

 ertheless belongs to an entirely different family. H. 

 2.0 to 2.5. G. = 1.5 to 1.6. 



FOURTH ORDER. 



METALLIC SALTS. 



Green Vitriol Copperas Sulphate of Iron. Found 

 in crystals, generally in clusters pulverulent or massive. 

 Glassy ; color greenish, passing into various shades of 

 white; subtransparent to translucent. Taste astrin- 

 gent, sweetish, and metallic. Decomposes slightly in 

 water ; effloresces if exposed to the air. and turns yel- 

 low. H. = 2.0. G. = 1.8 to 1.9. As green vitriol, 

 or sulphate of iron is the result of the decomposition of 

 pyrites, it occurs wherever they are met with, and the 

 most noted localities are found in old iron mines, where 



