PREFACE. 



The following pages presuppose for their comprehension some 

 acquaintance with geology and mineralogy. The materials for 

 them have been collected and arranged in connection with lectures 

 on economic geology, first at Cornell University and later at the 

 School of Mines, Columbia College. To the descriptions of others 

 the author has endeavored to add, as far as possible, observations 

 made by himself in travel during the last ten years. The purpose 

 of the book is twofold, and this fact has been conscientiously kept 

 in view. It is, on the one hand, intended to supply a condensed 

 account of the metalliferous resources of the country, which will 

 be readable and serviceable as a text-book and work of reference. 

 For this reason every effort has been put forth to make the bibliog- 

 raphy-complete, so that, in cases where fuller accounts of a region 

 are desired, the original sources may be made available in any 

 good library. But, on the other hand, it has also been the 

 hope and ambition of the author to treat the subject in such a way 

 as to stimulate investigation and study of these interesting phe- 

 nomena. If, by giving an extended view over the field, and by 

 making clear what our best workers have done in late years toward 

 explaining the puzzling yet vastly important questions of origin 

 and formation, some encouragement may be afforded those in a 

 position to observe and ponder, the second aim will be fulfilled. 

 In carrying out this purpose, the best work of recent investigators 

 on the origin and changes of rocks, especially as brought out by 

 microscopic study, has been kept constantly in mind, and likewise 

 in the artificial production of the ore and gangue minerals. So 

 much unsound and foolish theorizing has been uttered and believed 

 about ores, that too much care cannot be exercised in basing ex- 

 planations on reasonable and right foundations. 



Acknowledgments are due to many friends for encouragement, 

 suggestion, and criticism. To Prof. Henry S. Williams, now of 



