^ 



I 





V 



T t I, 



iii 





ft* I**- 







It 



r 



t 



xf 



■ ■) 



■ll,. 



lyv 



' J » 



Sect. VIIL] 



MINERALOGY. 



231 



They may be divided into the following:— 



1. Resins, 2. Bitumens. 3. Fossil combustibles, comprising an 



thracite, coal, lignite, and peat. 



Genus, 



XXV. Resins, 



Genus. 



Genus. 



Lxvi. Bitumens. 1 lxtii. Fossil combustibles 



. ^ 



O 



Under these 67 heads are now classed more than 500 

 minerals, supposed really to differ sufficiently to be 

 separated, independently of many merely considered 

 varieties, or accidental. 



It will be obvious that a voyager, especially when his 



as 



general time may he occupied with other duties, (only a 

 portion of it applicable to mineralogy, and that irregu- 



) 



e 



himself ftimiliar with all 



^V 



found he will have little difficulty, and by practice he 

 will readily detect them when presented to his attention. 

 Those which form the constituents of rocks it is especially 

 necessary to learn and distinguifh, since so much of 

 geological importance often turns upon their proper de- 

 termination. Those which are referable to the useful 

 class should engage his attention, since while, on the one 

 hand, valuable ores of the useful metals and other im- 

 portant substances are often neglected (even in our mining 

 districts unusual though valuable ores have been thrown 

 away at no remote times), on the other, many a mineral, 

 commercially worthless, is treasurt^d up, often even to 

 the neglect of those of high value, some particular bril- 

 liancy of appearance or fancied resemblance to precious 

 or metallic substances having; misled the collector. 



However desirable it may be to consider inorganic 

 matter as a whole, the conditions under which its parts 





^ 



