20 PROCEEDINGS OF THE WASHINGTON MEETING 



the exceptional experience of ten years on the Fortieth Parallel Survey ; 

 indeed, the monograph shows the influence of the earlier work and his 

 method of thought. Nowhere is this more clearly shown than in his 

 decision to acquaint himself with the geology of the Mosquito Eange 

 before taking up such intricate problems as the ore deposits undoubtedly 

 presented. He felt he might be led into error or fail to grasp essential 

 phenomena of ore deposition unless familiar with the structural features 

 of the adjacent country. This mental attitude of Emmons has been 

 well brought out by Whitman Cross, his field assistant and daily com- 

 panion at Leadville. Emmons conquered in a masterly way the details 

 of the complex ore bodies, and he undertook to solve no problems until 

 he assured himself that he knew his ground. Even as early as the 

 autumn of 1880, in his report to the Director of the Survey, he presented 

 many essential features of the region. An abstract of the monograph on 

 the geology and mining industry of Lead^dlle, accompanied by an ad* 

 mirable geological map, was published in the Second x\nnual Eeport of 

 the Director, and served to meet the needs of the engineers working on 

 the ground. The monograph itself, however, was held back for finishing 

 touches and the results of chemical investigation, although the method 

 of presentation and final conclusions remained essentially the same. 



The monograph and atlas, containing 35 sheets of maps and sections, 

 appeared in 1886. It attracted immediate attention not only of geolo- 

 gists and practical mine workers, but of all classes of scientific men. It 

 won for its author an international reputation, being received both in 

 Europe and America as a work of the highest order. Since its organiza- 

 tion, practically no single publication of the Geological Survey has ex- 

 erted a more beneficial influence and stimulated more discussion. It 

 everywhere aroused investigation of the origin of ore deposits, and simi- 

 lar studies were prosecuted elsewhere throughout the nortliern Cordil- 

 lera. The volume became a model for younger economic geologists. 

 One thing which greatly aided the success of the monograph was the 

 masterly, orderly way in which the author arrayed his facts, and the 

 clear, concise English in which they were presented. After twenty 3Tars 

 of active mining operations at Leadville and the exploitation in many 

 directions of new ore bodies, Mr. Emmons, aided by Mr. John D. Irving, 

 renewed his investigations, with the intention of bringing the earlier 

 work up to date. Under the title of the "Downtown District of Lead- 

 ville, Colorado," the salient features of this reexamination, with the light 

 thrown by new discoveries, were issued as a bulletin of the Geological 

 Survey, both names appearing as joint authors. Owing in part to the 

 failing health of Mr. Emmons, the completion of this study has been 



