XX REPORT OF THE STATE GEOLOGIST. 



manded would necessarily make it somewhat slow. This, however, would 

 not in any way impede your own operations in topography and secondary or 

 tertiary triangulation." 



The co-operation thus secured will be of the greatest benefit to our 

 work in Trans-Pecos, as it will enable us to take up the topographic 

 mapping of detached areas according to their importance and to con- 

 nect them by doing the intervening flats and less important portions 

 more at leisure. 



CO-OPERATION OF THE UNITED STATES GEOLOGICAL SURVEY. 



The work of the United States Geological Survey in this State dur- 

 ing the years 1889 and 1890 was as follows : 



18S9. In topographic mapping surveys were completed for sheets 

 covering approximately the counties of Shackelford, Palo Pinto, Par- 

 ker, Tarrant, Dallas, and Johnson. 6 sheets. 



1890. Sheets covering approximately the counties of Concho, Tay- 

 lor, Kunnels, Jones, and parts of Falls, McLennan, Hill, Coke, and Tom 

 Green. 8 sheets. 



This, together with the twenty-three sheets already surveyed, twenty- 

 one of which have been engraved, gives us a total of thirty-seven sheets, 

 representing an area of nine and a quarter square degrees, or about 

 forty thousand square miles. 



During the past field season the work in this State has been in gen- 

 eral charge of Mr. R U. Goode, Geographer. It has been prosecuted 

 by four parties as follows : 



Triangulation party, in charge of Mr. C. T. Urquhart. 



Party for establishing primary levels, in charge of Mr. A. E. Wilson. 



Two topographic parties in charge of Messrs. H. L. Wallace and H. 

 0. Gordon, respectively. 



In astronomic work Prof. R S. Woodward, assisted by Mr. A. P. 

 Davis, determined the location of the 105th meridian of west longitude 

 at a point east of the town of Sierra Blanca, Texas. This was effected 

 by first determining an astronomical position at Sierra Blanca, the lon- 

 gitude being ascertained by telegraphic exchange of time signals with 

 the observatory at Washington University, Saint Louis, and the lati- 

 tude by the method of zenith distances. From the astronomical 

 position, longitude 105° 21' 24" west, latitude 43° 35' 58" north, thus 

 determined, the 105th meridian was located by triangulation, and a 

 zenith mark on the meridian established. 



