BETWEEN MOSQUITO AKD BALL MOUNTAIN FAULTS. 217 



Coal in Weber Shales. — The carbonacGOus becls of the Weber Shales series 

 are unusually well developed in this region and often contain considerable 

 impure anthracite. The greatest developments of this coal are found in the 

 Ellesmere (B-2) and Little Providence (C-8) shafts, in the former of which 

 it is said to have a thickness of eighteen inches and in the latter of seven feet. 

 The coal, however, has thus far proved too impure to be of economic 

 value. Similar beds of coal have been observed by the writer at what is 

 very probably nearly the same horizon in the Pancake Mountains west of 

 White Pine, a short distance from Argenta on the Central Pacific Railroad, 

 and some 30 miles north of Elko on Coal Creek, in Nevada. Explora- 

 tions at all these localities have, howevei', failed to develop any workable 

 beds of good coal. In a region like Colorado, therefore, where the Creta- 

 ceous formations which are known to contain abundant beds of excellent 

 coal are so widely developed, it seems scarcely advisable to spend much 

 labor in searching for coal at this lower horizon. The name "Carbon- 

 iferous," which was given to this formation in the early days of geology, 

 when it was supposed to be the only coal-bearing horizon, is a practical 

 misnomer in the Rocky Mountain region, and apt to mislead the untechnical. 



Blue Limestone. — The outci'op of Bluc Limestone from the point where 

 the Ball Mountain fault crosses South Evans gulch, just below the Seneca 

 sliaft, follows up the nortli bank of the gulch and then bends to the south up 

 Alps gulch to the saddle between Ball Mountain and East Ball Mountain. 

 Its existence is proved b}^ explorations of the Little Rische (Gr-6), Little 

 Ellen (G-5), Lulu(G-4), Izzard (G-3), Gnome (G-2), Wall Street (G-1), 

 Dauntless (C-13), and Alps shafts, which have cut througli the overlying 

 White Porphyry to the contact. In the Little Ellen alone has any con- 

 siderable bodv of ore been discovered at the contact. Iron vein material 

 of considerable thickness has been found on the contact in the workings of 

 the Alps group of mines, but as far as known little rich ore has been devel- 

 oped. The White Porphyry is here very thin, and at the head of Alps gulch 

 disappears entirely, coming in again on the south side of the ridge. From 

 this saddle the outcrop of the Blue Limestone sweeps round to the eastward 

 to the Black Hawk shaft. This shaft passed through 80 feet of White Por- 

 phyry and a little black sliale before reaching the Blue Limestone. Beyond 



