COLOEADO. 481 



ward, underlie tlie plains to an unknown but doubtless very great extent. 

 With tliese are associated the beds of iron ore and fire-clay, while the 

 elevated portion of the range is traversed from north to south by the min- 

 eral belt, or system of lodes, in which occur the precious metals, gold and 

 silver, in combination with lead and copper. 



Coal and Iron. — The coal and iron deposits of the Territory have been 

 studied with much attention by Dr. F. V. Hayden, United States Geologist, 

 in charge of the Geological Survey of Colorado and New Mexico, who has 

 published some of the results of his investigations in Silliman's Journal of 

 March, 1868, and in his Preliminary Field Report, presented to the Secre- 

 tary of the Interior in 1869. According to this observer, these beds are of 

 Tertiary age. The coal is a lignite of very superior quality. The beds are 

 exposed in many localities all along the eastern base of the mountains, not 

 only in Colorado but in the neighboring Territories, the area covered by 

 them, north of the Arkansas River, being estimated at 5,000 square miles. 

 For a minute description of the geological features of this formation the 

 reader may be referred to Dr. Hayden's official report, from which is taken 

 the following section, showing the series of beds at Marshall's coal mine, 5 

 miles south of Boulder City and 17 miles north of Golden City, where the 

 largest developments of the Tertiary coal-bearing strata are revealed: 



48. Drab clay, with iron ore along the top of the ridge. 



47. Sandstone. 



46. Drab clay and iron ore. 



45. Coal (No. 11), undeveloped. 



44. Drab clay. 



43. Sandstone, 15 to 20 feet thick. 



42. Drab clay and iron ore. 



41. Coal (No. 10), undeveloped. 



40. Yellowish-drab clay, 4 feet. 



39. Sandstone, 20 feet. 



38. Drab clay, full of the finest quality of iron ore, 15 feet. 



37. Thin layer of sandstone. 



36. Coal (No. 9), nearly vertical, 12 feet. 



35. Arenaceous clay, 2 feet. 

 61 



