INTRODUCTION 



The territory assigned to the middle division for the season of 1873 

 was thus outlined in the letter of instruction given to Mr. Gannett, who 

 was in charge, on taking the field : 



" The boundaries of the area to be mapped by your division (or as 

 much of it as the season will allow) are as follows : Commencing at the 

 intersection of meridian 109° 30' and the Grand River, the line runs 

 northeastward up the Grand River to the junction of the Eagle River; 

 thence up the Eagle River to the mouth of Roche Moutonnee Creek; 

 thence westward along the northern boundary of last summer's (1873) 

 work to its intersection with meridian 107° ; thence southward along 

 the western side of last summer's work, approximately on the 107th 

 meridian, to parallel 38° 30' ; thence westward on this parallel to the 

 intersection of meridian 109° 30' ; and thence northward on this merid- 

 ian to the intersection of 109° 30' with Grand River." 



This area has an irregular boundary, Grand River, on the north, and 

 includes between 7,000 and 8,000 square miles, of which about 5,300 

 square miles were actually worked during the season. The area is 

 bounded on the west by the Uncompahgre and Gunnison Rivers, leav- 

 ing the area west of these streams for another season. This gave us a 

 well-defined natural boundary as our western limit. The greater por- 

 tion of the area is plateau country, the elevation of which ranges from 

 9,000 feet to 11,000 feet above sea level. The mountainous portion is 

 limited to the southeastern part, along the western edge of the Elk 

 Mountains. The drainage is comprehended in two systems, viz, that of 

 the Grand River and that of the Gunnison River. 



The entire district is within the limits of the reservation for the Ute 

 Indians, and a large portion of it had never been visited by white men. 



In 1853 Captain Gunnison, exploring for a route for a Pacific Railroad, 

 surveyed a belt of country along the river that now bears his name. In 

 the winter of 1853-'54, Col. John C. Fremont passed over nearly the 

 same route that Gunnison did. In 1845 Fremont followed the Arkansas 

 to its head, crossed Tennessee Pass (called Utah Pass by him), to the 

 Piney (Eagle), and followed it for some distance, finallycrossing to the 

 Blue (Grand River), and continuing westward. In 1873 Lieutenant 

 Ruffner followed Ohio Creek to its head, crossed to the head of Anthra- 

 cite Creek, and thence to Slate River, going eastward to the Arkansas. 



All these were merely reconnaissance surveys, and added but little to 

 our knowledge of the country outside of their routes. The great mass 

 of country lying between was unexplored. 



The general geological features of the district will be given in subse- 

 quent chapters. The greater portion of the district is covered with 

 rocks of Tertiary and Cretaceous age, covered in places with lava- 

 flows. 



Mr. Gannett's report will give all details in regard to the elevations 

 of peaks and passes, and topography of the country. 



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