16 



bv a vast fresh-water lake. Abundance of evidence is found to prove that 

 the region was then inhabited by animals as numerous and varied as those of 

 any other fauna, recent or extinct, in other parts of the world. Then, loo, a 

 rich tropical vegetation covered the country, in strange contrast to its present 

 almost lifeless and desert condition. 



The country appears to have undergone slow and gradual elevation ; and 

 the great Uintah lake, as we may designate it, was emptied, apparently in suc- 

 cessive portions and after long intervals, until finally it was drained to the 

 bottom. 



The ancient lake-deposits now form the basis of the country, and appear 

 as extensive plains, which have been subjected to a great amount of erosion, 

 resulting in the production of deep valleys and wide . basins, traversed by 

 Green River and its tributaries, which have their sources in the mountain 

 boundaries. From the valley of Green River the flat-topped hills rise in suc- 

 cession as a series of broad table-lands or terraces, extending to the flanks of 

 the surrounding mountains. 



The snows of the Uintah, Wahsatch, and other mountain-ranges are a 

 never-failing source to the principal streams ; but many of the lesser 

 branches, dependent for their supply on the accumulated snows of winter in 

 ravines of the lower hills and -plains, completely dry up as the snows disap- 

 pear with the approach and advance of summer. The country for the most 

 part is treeless and destitute even of large shrubs, excepting along some of 

 the water-courses. The principal streams are fringed with trees, consisting of 

 cotton- wood (Populus angusti folia) and willow, (Salix long i folia ;) and the 

 valleys through which they run produce mostly rushes (Juncus balticus) and 

 sedges, with some coarse grasses, as Elymus condensatus and Triticum repens. 

 Hollows of the hills and narrow valleys, favorable to the retention of moisture, 

 support forests of small aspens, {Populus tre?nuloides.) The higher terraces 

 and foot-hills approaching the mountain-ranges are covered with dense forests 

 of aspens, pines, (Pinus ponder osa and P. Jlexilis,) and firs, (Abies Menziesii, 

 A. Engebnanni, A. grandis, fyc.,) with a rich undergrowth of herbaceous 

 plants. The great mountains themselves present a broad belt of pines and 

 firs, from which project the rocky summits as bare of vegetation as the wide 

 plains at their base. Many of the lower hill-sides and hollows in certain 

 situations are sparsely covered with cedars, {Juniperus virginiana,) most of 



