GEOLOGICAL SURVEY OF THE TERRITORIES. 535 



beds between the bluifs and the center of the anticlinal valley, hardly 

 under 300 or 400 feet, and we have over 1,000 feet for the thickness 

 of this formation. It seems probable that in its upper portion it con- 

 tains some coal-seams, as at one point on the railroad, about four or 

 five miles east of Salt Wells, I observed an isolated outcrop of coal 

 in the bottom of a ditch alongside the track, which, from its posi- 

 tion, I judged to be below the heavy sandstone series. No seams 

 were seen in any of the other outcrops near the track or in the 

 bluffs. 



EocK Springs. — Passing westward from Salt "Wells we find on the 

 other side of the valley the great series of variegated sandstones and 

 clays re-appearing, but with a reversed dip to the northwest of some 10° 

 or 1^. Below it we have a considerable exposure of the thin sandstone, 

 which here appears to stand in more perpendicular faces than on the 

 opposite side of the valley, and has a more reddish cast. The sandstones 

 and clays immediately above, which on the eastern slope of the fold 

 showed no very numerous or valuable seams of coal, here appear to be 

 the great repository of that material 5 the lowest seam worked, that at 

 the Yandyke mine, is apparently only a short distance, perhaps a few 

 hundred feet, above the base of the series, and other veins occur within 

 short vertical distances of each other immediately above it. We made 

 no detailed section on this side of the anticlinal, but from our examina- 

 tions we judged that no very close parallelism existed between the beds 

 of the two slopes, although the series preserved the same general char- 

 acters on both. The principal coal-seam worked at Eock Springs, from 

 9 to 11 feet in thickness, overlies a heavy bed of bluish-white sandstone 

 very similar to many of those noticed farther east. The record of an 

 artesian boring made at the mines gives, as it was reported to me, some 

 sixteen seams of coal, varying from 18 inches to 8 feet in thickness,, 

 passed through in a depth of not more than 730 feet. Some of these 

 may, perhaps, be only beds of carbonaceous shale, but it seems to be 

 beyond question that the coal-seams are better developed here than 

 farther east. Still other veins occur in a higher horizon than was met 

 with in the boring, but they are of less importance. Opposite the sta- 

 tion at Eock Springs, on the opposite side of Bitter Creek, a heavy 

 bedded sandstone of perhaps several hundred feet in thickness appears 

 in the rocky face of a bluff and occuj^ies a considerably higher geological 

 position. This may j)ossibly be the equivalent of the heavy sandstone 

 near Point of Eocks, to which it bears a resemblance, but I am not inclined 

 to positively identify disconnected beds in this formation. It seems, 

 however, to be not far from the same relative position to the base of the 

 series. 



Some distance below the principal coal-seam at Eock Springs, 50 to 

 100 feet, or even more, we found a thin seam of hard sandstone, con- 

 taining a great abundance of certain species of fossils, a strongly ribbed 

 species of Corhula,a3Iodiola, and a Goniohasis, similar to those found near 

 Point of Eocks, and a few imperfect specimens of Ostrea. There are 

 other fossil-bearing beds in the vicinity, of which we heard accounts, but 

 our specimens were all gathered in this stratum. 



West of Eock Springs the ledges of this formation may be seen on 

 either side of the railroad for a distance of five or six miles, dipping to 

 the northwest or west- northwest at very much the same angle as near 

 the station. There is not, however, a good continuous exposure, but 

 the upturned edges of the harder beds form slight ridges above the gen- 

 eral level of the valley which intervenes between the station and the 



