318 GEOLOGICAL SURVEY OF THE TERRITORIES. 



Of course we have no certain means of determining whether we ought 

 not to call this shell Amnicola gregaria, or Pomatiopsis gregaria, instead 

 of referring it to Bythinella, the distinctions between these groups being 

 mainly based on characters not apparent in the shell. The fact, how- 

 ever, that it is found in vast numbers associated with a small Planorbis, 

 and millions of the carapace-valves of a minute Gypris, would seem to 

 indicate that it was aquatic in its habits, like Bythinella and Amnicola, 

 It is true, terrestrial shells are often swept by streams into lakes, and 

 deposited along with those of aquatic species; but it is exceedingly im- 

 probable that millions of so small a terrestrial shell as this would have 

 been deposited all together, so as almost to form an entire bed of liraf > 

 stone, especially without some other terrestrial types. 



Locality and position: : Pacific Springs. Tertiary. 



IL—ON THE TERTIARY COALS OF THE WEST. 



By Jas. T. Hodge, Geologist. 



The occurrence of coal in the Eocky Mountains was observed and re- 

 ported on by most of the early explorers on the different routes they 

 traversed across the continent. Little importance, however, was at- 

 tached to these discoveries, and, as the coal-beds were seen only in 

 their outcrop, little knowledge was acquired of their real character. It 

 was understood that they belonged, not to the true coal formation, but 

 either to the lower tertiary or upper cretaceous, and the coal was conse- 

 quently classed among the lignites or brown coals, and generally con- 

 sidered to be far inferior in quality to the genuine coals of the Eastern 

 and Middle States. As the country began to be settled, the scarcity of 

 timber soon caused these deposits of fuel to be looked up, and mines of 

 coal to be opened and worked in Utah and in Colorado. The construc- 

 tion of the Union Pacific and Central Pacific Bailroacls created a still 

 greater demand for fuel for the supply of their locomotives, and new 

 mines were opened along the line of the former road in Wyoming Terri- 

 tory, which, with those worked on the eastern border of Utah, near the 

 same road, supply both these long lines of road with all the coal they 

 require. No mines have been found near the Central Pacific Railroad, 

 either in Utah, Nevada, or California, so that this road is wholly depend- 

 ent for fuel upon the coals brought to it from the Union Pacific. Though 

 it is scarcely three years since these coalmines began to be developed, 

 they have already produced large quantities of coal, and several among 

 them have tlie appearance of thriving collieries, well furnished with 

 powerful machinery for pumping and hoisting, and all the appliances 

 of first-class establishments. 



In Colorado, mines were opened along the eastern base of the Eocky 

 Mountains about eight years since, and a number of them have been 

 worked to a moderate extent from that time, supplying Denver and the 

 settlements below the mountains. The coal was found very serviceable 

 for domestic purposes, but was deficient in caloric quantities, such as 

 are required for founderies and other metallurgical works. The writer 

 in 18(33 found the blacksmiths for the most part unable to produce a 

 welding heat with the coal in their forges, and coke was brought from 

 Kansas for a foundery at Black Hawk at an expense of $100 per ton. 

 The coal-mines were then esteemed of very little value. The opening of 



