70 REPORT OF THE SECRETARY. 



beeu surveyed by the public land system, use miglit be made of the plats 

 of the General Land Office, whereby without sacrificing accuracy the 

 work might be greatly facilitated. For the control and correction of 

 the surveys of the General Land Office it was decided tentatively to 

 use astronomic locations, and these Mr. E. S. Woodward, formerly of 

 the U. S. Lake Survey, was directed to determine. As shown by the 

 table already given, an area was surveyed in this sub-section, during 

 the two years, of 37,000 square miles. In continuing the work in the 

 Missouri-Kansas sub-section during the last fiscal year, closing June 

 30, 188G, it was decided to substitute a gridiron system of triangula- 

 tion, utilizing as far as jiossible the trans-continental belt of the U. S. 

 Coast and Geodetic Survey, in place of astronomic determinations, for 

 the correction of accumulated error in the surveys of the General Land 

 Office. Satisfactory i)rogress was made in the Texas and Arizona sub- 

 sections, but work was impeded in the Gold Belt and Cascade sub- 

 sections by unfavorable at mospheric conditions during the latter i^art 

 of the last season. Notwithstanding these drawbacks an area of more 

 than 50,000 square miles was surveyed during the last fiscal year. 



Yellowstone Section. — During the two years under review topographic 

 work was continued in the Yellowstone National Park, and an area of 

 1,000 square miles was surveyed in the first year, and 3, GOO in the sec- 

 ond, the latter figure including a portion of Northwestern Wyoming. 



Engraving. — The manuscript of seventy-six sheets of the General At- 

 las of the United States, now in preparation by the Geological Survey 

 has been furnished to the engraver, and of these fifty-seven have been 

 engraved, comprising about 125,000 square miles. In the Seventh An- 

 nual Eeport of the Director of the Survey to the Secretary of the Inte- 

 rior a list is given of the sheets thus far engraved. 



GEOLOGY. 



The present organization of geologic work in the Survey will be ap- 

 prehended from an examination of the following condensed account of 

 the work of each of the divisions : 



Division of ArcJiean Geology. — Prof. Eaphael Pumpelly devoted his 

 time in the field to a study of the structure of the Green Mountains, 

 believing that range to contain the key to the geology of New England. 

 The structure of a long and important stretch of the Hoosac Mountain 

 in Massachusetts and Vermont was worked out, and Professor Pum- 

 pelly hopes by the end of another season to be in a position to solve 

 this great geologic problem. A large part of his office work was upon 

 the "Mining Industries" volume of the Tenth Census. 



Atlantic Coast Division of Geology. — In his study of the geology of 

 the Atlantic coast Prof. N. S. Shaler has addressed himself especially 



