GEOLOGICAL SURVEY OF THE TERRITORIES. 3G7 



large extent. The consumption from Denver and cities aronnd is -esti- 

 mated at about four hundred tons per day. The lignite-bank of Erie 

 can supi)ly, for an indefinite time, the demand of the Kansas Pacific 

 Eailroad, while the Denver and Eio Grande Kailroad has now a full 

 supply from the Caiion City coal-bed, and a large overplus left for the 

 Denver market or any other on its line. 



It is evident, therefore, that there is for the present more danger of a 

 glutted market than of a scarcity of combustible material, and that for 

 the future the settlements in the valley of the Eocky Mountains, and 

 especially along their eastern base, may rely on a permanent and ciieap 

 supply of coal. I should admit the same conclusion even in considering 

 that the settlements along the Kansas Pacific Eailroad from Den- 

 ver to the limits of Kansas will hav^ to get their fue> from the same 

 source. The estimate in tons of the average productiveness of a bed of 

 bituminous coal of the old measures, is generally marked at one million 

 of tons per foot of thickness in one square mile. Counting a single bed 

 of lignite of the Eoulder Valley at 9 feet thick, extended over a surface 

 of only twenty-five square miles, what should we find ? Deducting one- 

 fifth for difference in density between bituminous and lignite coal, or 

 admitting only eight hundred thousand tons per foot of thickness in a 

 square mile ; deducting still from this amount one-half for drawbacks 

 in mining, the result would be four hundred thousand tons per foot of 

 lignite in a square mile, or for 9 feet three million six hundred thou- 

 sand tons, and in an area of twenty-five square miles, ninety millions of 

 tons obtainable from a comparatively limited extent of the Lignitic basin. 

 Though I believe that this estimate is below the reality, calculations of 

 this kind can never be positively reliable, and should be admitted with 

 due caution. It is, however, of the greatest importance for the pro- 

 prietors, and for the consumers too, to positively know the capacity of 

 the lignite-beds, in order to regulate the mining, and to fix rates of 

 price advantageous to both parties. 



§4. The Lignite-Deposits along the Union. Pacific Eailroad 



FROM Cheyenne to Evanston. 



The distribution and capacity of the lignite-beds of this section have 

 been reported already in considering the geological distribution of the 

 Eocene formation. The essential supply of coal, either for the railroad 

 or for the demand along its line, has been, and is still, obtained fiom 

 Carbon, Eock Springs, and Evanston. The beds of lignite at Carbon 

 are distributed in three separate basins of limited extent. Two of 

 these have furnished already abundant materials, being mined since the 

 beginning of the construction of the railroad. iSTo data have been 

 obtained snfliciently precise to allow an estimate of the productive 

 capacity of the Lignitic strata there still obtainable for ex])loitation. 

 The superintendent of the mines remarks that the (!oal is difficult to 

 work, being unreliable and cut by faults and irregularities. Moreover, 

 the mine has been ignited by spontaneous combustion of the slack coal, 

 and been on fire for a length of time. JTow the amount of coal obtained 

 from Carbon is about three hundred tons daily. 



At Eock Spring the vein of lignite is still thicker than at Carbon, 

 and the material of very fine quality. It has been, and is now, mined 

 in the same proportion as at Carbon. The productive capa(;ity of this 

 basin is still very great, especially comsitlering the amount of coal which 

 could be obtained from lower beds by shafts. The area covered by the 

 upper bed is, however, limited, and as this bed is now mined by three 



