MINERALOGY. 393 



cates their composition. The complete analysis of minerals, requires 

 a thorough acquaintance with all the resources of chemistry. 



3. Under the head of Systematic Mineralogy, we are to speak 

 briefly of the different systems according to which minerals have 

 been classified and named. The object of the chemical system, is 

 to place together those minerals which most resemble each other in 

 composition ; while that of the natural system, is to associate those 

 which most resemble each other in their general properties. The 

 chemical classification, adopted by several writers, usually com- 

 mences with the non-metallic minerals, the gases, combustibles, and 

 non-metallic acids : proceeding next to the salts ; both the soluble 

 salts, or those commonly known as such ; and the earthy salts, or 

 earths; which are mostly salts of silicic acid : and the list is usually 

 completed by the higher metals, and their various ores ; of which 

 the oxides and sulphurets are the most important. 



In the natural classification, as proposed by Mohs, and modified 

 by Dana, all minerals are divided into three classes : Epigsea, or 

 minerals found mostly on the earth's surface, as gases, acids, and 

 soluble salts, of all of which, the specific gravity is less than 3-8 : 

 Entogxa, or minerals found mostly within the earth ; insoluble and 

 tasteless, and all having a specific gravity above 1 8 : and Ifypogasa, 

 or minerals which were once on the earth's surface, being of vegeta- 

 ble origin ; but have since been buried ; as the coals and resins. 

 These classes are subdivided into orders; which we shall briefly 

 describe in the following section. The orders have been farther 

 subdivided into genera, and species, which we shall not in this work 

 have room to describe. We can only mention the most important 

 species, giving them their common or trivial names ; which are for 

 the most part arbitrary, and often derived from the names of indi- 

 viduals who have distinguished themselves in this science. 



4. Under the head of Descriptive Mineralogy, we proceed to 

 give some idea of the more prominent minerals, arranged according 

 to the natural orders of Dana ; with some remarks on their proper- 

 ties and uses. The first class, Epigaea, is divided into two orders, 

 Rheutinea, or fluids, and Sterinea, or solids. The order Rheutinea, 

 includes the native gases ; or carburetted hydrogen, which is the 

 same as coal, or oil gas ; phosphuretted hydrogen, which is sponta- 

 neously inflammable, and the cause of the ignis fatuus ; sulphuretted 

 hydrogen, known by its fetid odor; atmospheric air, essential to 

 animal life and ordinary combustion ; carbonic acid, or the choke 

 damp of mines, fatal to animals confined in it; and sulphurous and 

 muriatic acids, suffocating gases, evolved from volcanoes. This 

 order includes also the native liquids ; water, and sulphuric and mu- 

 riatic acids ; these latter being in a dilute state. The order of Ste- 

 rinea, or solids, includes boracic and arsenious acids, found sparingly; 

 borax, or borate of soda, useful as a flux to cause other minerals to 

 melt; alum, which is sometimes found native; solfatarite, or soda 

 alum ; natron, a hydrous carbonate and sulphate of soda ; common 

 salt, found in mines, springs, and the sea; Glauber's salt, and Epsom 

 salt, useful in medicine ; sal-ammonic, nitre, and the vitriols, useful 

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