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224 



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[Sect. VIIL 



Section VIII. 



MINEKALOGY 



By sir henry DE LA BECHE, C.B., F.E.S., &c. 



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A GLANCE at the best treatises on mineralogy, even 

 those wherein the matter is most condensed^ is sufficient 

 to show that a profound acquaintance with this science 

 can only be acquired by long-contliMied study, and by 

 means of a competent knowledge of certain other sciences, 

 the aid of w^hich must be obtained properly to com- 

 prehend the internal and external structure and chemical 

 composition of minerals. The naval man may never- 

 theless nccomplish much, more especially respecting the 

 mode of occurrence and probable origin of minerals under 



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to the catalogue of known substances of this class. 



When we see a diamond, we consider that we have 

 before us an arrangement of the particles of carbon in 

 the most perfect manner, that is, these particles have 

 been enabled freely to adjust themselves, so that they 

 have filially been aggregated in a definite form. So also 

 a ruby or a sapphire presents us with the particles of 

 alumina (with usually some slight admixture of other 

 substances, such as oxide of iron, silica, &c.) arranged in 

 a definite and most perfect manner, the conditions having 

 been such that they also could freely adjust themselves; 





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