GEOLOGICAL SURVEY OF THE TEREITOEIES. 135 



outsitte or above this, the bed of potter's clay, "which supplies the pot- 

 tery at Golden City. About midway in this series of beds an entrance 

 has been made exposing a second bed of coal. The surface is so grassed 

 over that it is quite impossible to make out the full series of beds 

 clearly, but the softer strata are well shown by the depressions between 

 the beds of sandstones. 



The north mesa is two and one-half miles long and about one mile 

 wide. The south one is four miles long and about a mile wide. This 

 one has an irregular surface and gradually slopes down eastward until 

 it becomes a low ridge of tertiary sandstones and clays. The wall of 

 basalt that surrounds the top is nearly perpendicular most of the way 

 round, from fifty to one hundred and fifty feet in height. The lower por- 

 tion of the basaltic bed on the north side of the south mesa is very vesicu- 

 lar, full of rounded porous masses somewhat like slag, and re "its upon the 

 slightly irregular surface of a bed of fine fire-clay, which contains traces 

 of vegetable remains. Below the fire-clay are alternate beds of sand- 

 stone and arenaceous clay, inclining slightly east, and evidently pro- 

 tected from erosion by the hard cap of basalt. These beds are plainly 

 tertiary lignite, and must be six hundred to eight hundred feet thick. 

 The lowest bed of vesicular basalt is evidently more recent than the 

 columnar bed above. 



Golden City is a thriving little town, located near the embouchure of 

 Clear Creek from the mountains, which is called the " Golden Gate." 

 Clear Creek Valley is very fertile, and, in looking down upon it from the 

 top of the mesa, it appears like a finely cultivated garden. The ridges 

 of upheaval or "hog-backs" near Golden City are small and unimport- 

 ant, owing to the erosion which has worn them down. But proceeding 

 southward a short distance they increase in size. The tertiary ridges 

 are most conspicuous until we reach Mount Vernon, about five miles 

 south of Golden City, where the older formations are largely displayed. 

 Here the tertiary beds are tipped past a vertical j)osition and seem to 

 incline toward the mountains; but this is more apparent than real; 

 tlie top portion leaning over, while deeper in the earth the strata incline 

 at a high angle from the mountains. 



Green Mountain is a lofty, grass-covered hill, and is entirely com- 

 posed of the coal strata, while to the west of it is a nearly vertical ridge 

 of sandstone. Just inside of this ridge, or beneath it, is a coal bed 

 which has been opened by Mr. John A. Eoe. The entrance to this mine 

 is the finest I have seen in Colorado, and is 170 feet in length, through 

 141 feet of sandstone with a slope of 45°. The sides and roof of the 

 entrance are not protected. The bed of coal is nearly vertical in position 

 at this point, though at some places where it is not wrought it inclines 

 east 70°. There are three seams of coal, 4 feet each, in thickness with 3 J 

 feet of clay intervening. Below the coal there is a bed of clay 5 feet thick, 

 and above 3^ feet arenaceous clay. The coal is close, compact, and makes an 

 excellent fuel, and Mr. Roe, who is an old Pennsylvania miner, considers it 

 better than the bituminous coals for all domestic purposes, but for generat- 

 ing" steam and smelting ores ho regards it as inferior. The ash is 

 white, resembling pine- wood ashes, and the quantity is small. The coal 

 at Murphy's, on Kalston Creek and Golden City, leaves a red ash. There 

 are no cinders, and in burning it gives a bright, clear flame ; and although 

 it burns iron, it does not give sufficient heat to weld it. I believe this 

 to be a continuation southward of the Golden City bed. It is also the 

 lowest of the coal strata in this region, for in the valley immediately 

 west and on the sides of the ridge can be seen the dark clays of the cro^ 

 taceous beds. This ridge is very high at this place, and is composed of 



