PREFACE. XXI 



entirely in harmony with stratigraphers, the delay has enabled us to pu1 our 

 evidence on such a basis of undisputed facts thai a final agreenienl can be 

 only ii question of time. While the economic data have lost somewhal in 

 freshness from the protracted delays in publication, due firsl to one cause 



and then to another, it is believed that this is re than offset by the 



increased definiteness which has accrued to conclusions upon various dis- 

 puted points, and thai the work will serve, as it was intended, to illustrate 

 the structural and economic conditions which govern not only the limited 

 area mapped, but also, to a greater or less extent, that of the entire plain 

 bell at the easl fool of the Rockj Mountains. It presents the fruits of the 

 labors of several individuals not mentioned on the title-page, and acknowl- 

 edgments are due to Mr. I''. II. Knowlton for a chapter on the flora of the 

 Denver beds, to Prof. 0. C. Marsh for one on the vertebrate fauna of 

 the held, to Mr. George L. Cannon, jr., for investigations of the Pleistocene 

 formations, and to the latter and Prof. Arthur Lakes for collections of ver- 

 tebrate and plant remains IV the Denver beds; also to Messrs. C. S. Slack 



■ and P. II. van Diesl for collecting data with regard to the location, depth, 

 etc., of artesian wells, which have been freely used in this report. To the 



] lv mine superintendents, foremen, and others, t Lumerous to mention 



by nam;', who have given in the most generous manner facilities and 

 information in furtherance of the objects of this work, thanks are also 



tendered. 



S. !•'. Emmons. 



