48 REPORT OF THE SECRETARY. 



under its care, than the topographic and strati graphic work; but the 

 whole possesses interest as being part of a common endeavor to develop 

 and disseminate scientific truth. 



Among the operations of the Survey that may be cited in this con- 

 nection are the following : 



Field studies upon the much discussed Laramie group have been 

 prosecuted in Eastern Montana and iSTortheastern Dakota, covering 

 particularly a belt of about 80 miles along the Upper Missouri, and up- 

 wards of 100 miles adjacent to the Yellowstone, resulting in large col- 

 lections and important stratigraphic data. Similar combined strati- 

 graphic and paleontologic investigations have been in progress upon 

 the paleozoic series of the Eureka and Pine River districts of Xevada, 

 with a view to the more certain determination of the stratigraphy of 

 those important mining regions. The exploration of the interesting 

 ancient lake deposits of the Great Basin has been continued, the silts 

 of the ancient Lake Lahontan being the special subject of study. The 

 Permian and Carboniferous strata of Northern Arizona, in the vicinity 

 of Kanab, have been further examined, and important collections made 

 from them. 



One of the more significant subjects of exploration was furnished by 

 the Grand Gaiion group, an immense series of 12,000 feet thickness, 

 now demonstrated to lie between the upper Cambrian and the crystal- 

 line Archaean rocks. Beside critical stratigraphic work, a large collec- 

 tion, involving a problematic organic form, was made, which yet awaits 

 exhaustive study. The investigations in the great mining districts of 

 Colorado and Nevada have been continued, with a view to supplement- 

 ing and perfecting the data previously gathered and the extension of the 

 work to new ground. 



Investigations have likewise been in progress upon the great metal- 

 liferous series of the Lake Superior region, including the practical com- 

 pletion of the work upon the copper-bearing formation, as at present 

 planned, and the commencement of that upon the iron-bearing series. 



In the interior basin, a special study of the great moraines that mark 

 the limit of the second glacial advance, and constitute datum lines 

 of great importance in glacial studies, has been in progress, and 

 about 3,000 miles of an essentially continuous morainic chain are now 

 mapped. 



In addition to these more comprehensive studies, special collectors 

 have been in the field, gathering fossils from localities of exceptional 

 richness, or from critical and decisive horizons. Among these have 

 been the collections of Tertiary fossils, especially vertebrates, from 

 Oregon, and of Jurassic and Eocene remains from Wyoming. A special 

 effort has also been made to secure a full representative collection from 

 the marine Tertiary beds of the Lower Mississippi Valley. 



Triangulation and topographic work, preparatory to geologic inves- 

 tigation, has been prosecuted in the quicksilver districts of New Alma- 



