GEOLOGICAL SUKVEY OF THE TERRITOJKIES. 335 



exposed iu the Mils soutlieast of the station. Some of them have a few 

 fossil dicotyledonous leaves. They overlie the bed of coal marked 4 

 feet in the section, the Van Dyke bed, which is opened and worked near 

 the railroad, two miles east of Eock Springs. 



When I passed Eock Spring a boring for an artesian well was still 

 in progress and had already reached 1,180 feet. Mr. Frank F. Phelps^ 

 to whom I am indebted for many kind offices and valuable information, 

 gave me the following records of this boring. Though the nature of the 

 strata separating coal-beds is not marked, some interesting deductions 

 may be furnished to discussion by the succession of the measures. 



At 7 feet from surface, after passing sandy soil and black shale : 



Ft. In. 



1. Main coal 8 



At 117 feet, after beds of hard sandstone, shaly sandstone, and soapstone, 



intercalated : 



2. Coal worked two miles east 4 



3. At 149 feet, coal 3 4 



4. At 268 feet, coal 5 5 



5. At 324 feet, coal 3 



6. At 353 feet, coal 2 6 



7. At 377 feet, coal 2 1 



8. At 420 feet, coal 3 



9. At 447 feet, coal 1 8 



10. At 476 feet, coal 2 G 



11. At 485 feet, coal 2 



12. At 577 feet, coal 2 6 



13. At 606 feet, coal . 3 



14. At 640 feet, coal 1 8 



15. At 668 feet, coal 1 8 



16. At 728 feet, coal 2 



Between all these coal-banks the strata passed through were constantly 

 soapstone and sandstone; the soapstone looking like blue fire-clay, but 

 more difficult to pass with the *bore than the sandstone. From 780 to 

 1,180 feet, the depth reached when I was there, the strata are merely 

 white sandstone, alternating with shale. 



This record seems to show an extraordinary or abiiormal development 

 of lignite-strata. We have here sixteen beds of this coal, measuring in 

 the whole 48 feet in thickness, in little more 700 feet of measures. This, 

 however, is not different from what has been seen elsewhere already, in 

 some exposures of the upper Lignitic formations. The section at Mar- 

 shall's, as published in Dr. F. V. Hayden's Eeport, (1869,) pp. 29 and 

 30, marks eleven beds of lignite, which, taken all together, measure 63 

 feet, and this in less than 600 feet, of strata, overlying the lower sand- 

 stone and exposed above surface. There is merely at Eock Springs an 

 increased thickness of the sandstone-beds, which is normal, and is easily 

 understood in considering the mode and development of the Lignitic 

 formation. 



From Eock Springs to the base of the hills north of the station, six 

 to seven miles distant, the bottom of the valley is nearly flat, bordered 

 by low ridges of shaly sandstone, passing to mere hillocks, an^ then to 

 sand and clay detritus from the northern, hills which overlie here the Lig- 

 nitic. They belong to the Green Eiver Group of Hayden, and appear in- 

 deed to form a distinct, well-characterized division of the Tertiary. My 

 purpose in visiting these hills was first to see a remarkable stratum, 

 mere compound of shells glued together by ferruginous and calcareous 

 clay, the whole mass mostly silicified. These molluscs, generally 

 small, appear fresh-water species, and of more recent types than those 

 which I had found in the black shale over the main coal of Eock Springs. 



