132 Mr. D. Forbes' s Researches on the 



siderably south of Santiago northwards up to the frontiers of 

 Bolivia in the desert of Atacama, and in inspecting all the prin- 

 cipal, and a great number of the lesser, mining districts scattered 

 along the range of the Cordilleras. 



These explorations enabled me not only to visit, with but 

 very few exceptions, all the mineral^ localities mentioned in Do- 

 meyko's ' Mineralogy'*, then the only work upon the subject, 

 but also to more than double the number of species therein de- 

 scribed as occurring in Chile. 



Such an investigation, as might be expected, gave me not 

 only the opportunity of forming an extensive and valuable col- 

 lection of minerals, but also of specially studying the occurrence 

 of the minerals themselves, with reference to the geological 

 position of the rock-matrix in which they were imbedded ; and 

 it was soon evident, upon comparing the data obtained, that, so 

 far from the appearance of minerals (using the word mineral 

 more especially to designate such compounds as differ from the 

 bulk of the rock-matrix) being, as is generally considered, acci- 

 dental, on the contrary, if we except only a small number 

 of more usually occurring compounds which are common to 

 a variety of circumstances, the others invariably presented 

 themselves under similar conditions, had the same associated 

 minerals along with them, and, when the geological age of 

 the eruptions in which they occurred could be satisfactorily as- 

 certained, frequently, if not always, corresponded in geological 

 age. 



In Chile, as elsewhere, the intrusive rocks, with their accom- 

 panying metallic lodes, furnish the greater number of mineral 

 species, and it was everywhere found that similar minerals, or 

 classes of minerals, accompanied the eruption of similar rocks. 



In the present communication, therefore, it is intended to 

 bring forward a statement of the mineral species met with in 

 Chile, and then to attempt a classification or grouping of the same 

 in accordance with the mode of what might be termed their 

 geological occurrence. 



The following enumeration represents probably as correct a 

 list of the Chilian mineral species, together with their chemical 

 formulsef, as can at present be attempted. 



* Domeyko has since published a second edition of his work, with con- 

 siderable additions; but the list of Chilian mineral species here brought for- 

 ward will be found still more extensive. 



t The formulae are all arranged according to the old notation, as the 

 pew has as yet not been generally adop'ted by mineralogists. 



