REPORT OF THE SECRETARY. 8? 



the jilacicrs and the accompanying phenomena weredeterminodMilh as 

 much accuracy as possible, and collections were made which enabled 

 Mr. Diller to indicate on the map, prepared at the same time by a topo- 

 graphic party, the distribution of the material forming the successive 

 flows. A large number of photographic views were also taken, which, 

 with field-notes and sketches, will be invaluable in setting forth the 

 geology and topography of this interesting region. 



Upon Mr. Diller's return from the field, a well -equipped petrographic 

 laboratory was fitted up under his direction in the Survey building, 

 and an opportunity thus afforded for the microscopic study of the col- 

 lections of the various divisions. In connection witli this laboratory it 

 was found possible to arrange abundant facilities for the preparation of 

 micro-sections. Under Mr. Diller's management most gratifying results 

 have already been obtained from this much-needed acquisition to the 

 Survey's equipment. In the last quarter of the year alone 512 micro- 

 sections were made. 



Goal-fields of the Great Sioux Reservation. — On January 3, the honora- 

 ble the Secretary of the Interior instructed the Director of the Survey to 

 have made a geologic survey of the Great Sioux Eeservation, for the 

 purpose of determining the extent and value of such coal-fields as might 

 be found. It was not practicable to undertake this task until the spring. 

 At that time the services of Mr. Bailey Willis were secured, and he, with 

 a party, was sent to Dakota. In addition to the geologic investigations 

 l^rosecuted by Mr. Willis, he also superintended the preparation of a 

 map of 2,000 square miles, embracing all of the area in which it was ex- 

 pected the so-called coal-fields would be found. Before the close of the 

 year Mr. Willis had completed his report, and it only awaited the prepara- 

 tion of the map to be forwarded to the Secretary of the Interior. While 

 the details of this report cannot be given here, it may be briefly stated 

 that the coal-beds were found to be confined to restricted areas, and to 

 be of but little if any value for commercial or domestic purposes. 



Geologic map of the United States. — The geologic map commenced in 

 1883 was completed and placed in the hands of the engraver. It was 

 found, after collating all available data, that our knowledge is not suffi- 

 cient to warrant the extension of geologic colors over the entire territory 

 of the United States. Accordingly, California, Oregon, and parts of 

 Montona, Idaho, Nevada, Utah, Arizona, New Mexico, and Texas re- 

 main uncolored. 



This map will be issued in two editions within a few months. The 

 first edition will be colored in accordance with the scheme previously 

 adopted and published by the Survey. It will form one of the plates of 

 theFifthAnnual Report of theDirector, and a brief explanatory statement 

 will accompany it. A second edition, with complete explanatory text, 

 will be issued as a bulletin. In this edition the map will be printed in 

 duplicate, one copy colored in accordance with the published scheme 

 and the other in accordance with a scheme now under consideration. It 



