MINERALOGY. 173 



and metals ; besides a vast number of useful minerals which 

 had been formerly unknown or disregarded. 



Nothing at first sight appears easier than to describe a 

 mineral, and yet in reality it is attended with a great deal 

 of difficulty. It is obvious, that to distinguish a mineral 

 from every other, we must either mention some peculiar pro- 

 perty, or a collection of properties, which exist together in 

 no other mineral. These properties must be described in 

 terms rigidly accurate, which convey precise ideas of the 

 very properties intended, and of no other properties. The 

 smallest deviation from this would lead to confusion and un- 

 certainty. Now it is impossible to describe minerals in this 

 manner, unless there be a peculiar term for each of their 

 properties, and unless this term be completely understood. 

 Mineralogy, therefore, must have a language of its own ; that 

 is to say, it must have a term to denote every mineralogical 

 property, and each of these terms must be accurately defin- 

 ed. The language of mineralogy was invented by the ce- 

 lebrated Werner, of Freyburg, and first made known to the 

 world by the publication of his treatise on the External Cha- 

 racters of Minerals. The object of this philosopher was to 

 invent a method of describing minerals with such precision, 

 that every species could readily be recognised by those who 

 were acquainted with the terms employed. For this pur- 

 pose, it was necessary to make use of those properties only 

 which presented themselves to our senses on inspecting the 

 mineral. These accordingly were chosen, and called by 

 Werner external characters ; because they may be ascer- 

 tained without destroying the mineral examined. These 

 constitute the first division of the characters of minerals. 

 To the second belong those which are derived from the 

 chemical composition, or discovered by any chemical change 

 which the mineral suflfers ; to the third are referred those 

 properties which are afforded by certain physical characters, 

 as electricity or magnetism ; and to the fourth a few charac- 

 ters, derived from circumstances frequently observed with 

 regard to a mineral, as the place where it is found, or the. 

 minerals by which it is usually accompanied. 



Questions. — 1. What are minerals? 2. What is mineralogy ? 



3. What is said of the knowledge which the ancients had of minerals ," 



4. What has been the state of this science since the year 1770 ? 5. 

 How must minerals be described i G. What was the object of Werner 



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