74 PEOCEEDIXGS OF THE AXX ARBOR MEETIXG 



MERGING OF THE CARLILE SHALE AXD TIMPAS LIMESTONE FORMATIONS IN 



S O U THE AS TERN COLORADO 



BY H. B. PATTOX 



Eead by title. 



PRESENT STATUS OF THE GEODETIC WORK IN THE UNITED STATES AND ITS 



VALUE TO GEOLOGY 



BY WILLIAM BOWIE 



i Abstract) 



The geodetic work of the United States, now carried on by the United States 

 Coast and Geodetic Survey, is supplemented to a small extent by the Topo- 

 graphic Branch of the United States Geological Survey and by several cities. 

 There are now in the United States, in addition to the coast triangulation, 

 20,000 miles of arcs of precise triangulation and traverse, furnishing the geo- 

 graphic positions of many thousands of points or stations. Precise leveling 

 was begun in the United States by the War Department in connection with 

 river improvements and control. Later, this work was begun by the Coast and 

 Geodetic Survey to furnish accurate elevations for the reduction to sealevel 

 of measured base lines. There are now 47,000 miles of precise leveling in the 

 United States, furnishing the elevations of 18,500 bench-marks. The triangu- 

 lation and precise leveling are essential in the preparation of accurate topo- 

 graphic maps, without which geologists carry on their field-work with great 

 difficulty. A modification of the von Sterneck type of pendulum was made in 

 the United States Coast and Geodetic Survey, under the direction of Dr. T. C. 

 Mendenhall, then Superintendent, which has been used to determine the in- 

 tensity of gravity at 300 stations in the United States. The geologists are 

 interested in the gravity work because the data furnished by the observations 

 have been extensively used to supplement the isostatic investigations based on 

 triangulation and astronomic data. 



The geodetic data furnish accurate physical measurements of direction, dis- 

 tance, and force, which are more effective than any other means in throwing 

 light on the constitution of that part of the crust of the earth which is beyond 

 the possibility of direct observations and measurements. 



Presented in abstract extemporaneously. 

 Brief remarks were made by Mr. David White. 



RECONNAISSANCE TRAVERSE FROM MOJAVE ULOJANE. CALIFORNIA, TO 



ROCK CREEK. UTAH 



BY HERBERT E. GREGORY 



(Absti'act) 



The work described includes location of fault south of Death Valley ; tracing 

 Mesozoic from Spring Valley Mountains to mantle of San Juan; restudy of 

 the Kanab section of Walcott; definitions of the "Marine Jurassic" and 

 Kaibab ; and extension of the Supai-Hermit unconformity. 



Presented in abstract extemporaneously. 



