368 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



the absence of such a classification. The object of a system of classifica- 

 tion is not only to afford a means of avoiding long and repeated circum- 

 locutions in descriptions, but also to furnish a comprehensive view of the 

 mutual relations of the classes of phenomena to which it is applied. Such 

 systems must necessarily change from time to time as the scientific studies 

 of the phenomena progress and knowledge with regard to them becomes 

 more accurate and thorough. The unsatisfactory state of existing classifi- 

 cations of ore deposits is due in large degree to an imperfect knowledge of 

 the subject on the part of those who have made them, but in part also to 

 their being made from a false standpoint. 



As the study of geology sprang originally from the empirical observa- 

 tions of those engaged in mining for the useful metals, so the first systems 

 of classification of ore deposits were based on distinctions and character- 

 istics established by the miners themselves in their daily work, and, as in 

 carrying on this work the outward form of the deposit was the most essen- 

 tial characteristic, this naturally formed the basis of their classifications. 

 But while general geology has made relatively more rapid progress than the 

 study of ore deposits, which, being a matter of practical and economic im- 

 portance, has seemed to many to belong to a lower sphere of scientific inves- 

 tigation than purely theoretical questions, the prevalent classifications still 

 hold largely to the original basis of the practical miner. The form of a 

 deposit might well constitute the basis of a classification, if it constituted 

 an essential characteristic thereof, and if there were certain regular forms 

 that belonged exclusively to particular classes of deposits, which had a 

 necessary connection with the sum of their other characteristics. This is 

 so far from being the case, however, that not only is no one form confined 

 to any particular class of deposit, but the same class of deposit, that is, 

 one which has undoubtedly the same origin and manner of formation, may 

 have a great variety of different forms, as is the case with those about to 

 be described. 



That the scientific study of ore deposits has not kept pace with the 

 advance in other branches of geology is due in great part no doubt to the 

 inherent difficulty of the subject, but also in a measure to a want of scien- 



