PHYSICAL FEATURES OF COLORADO VALLEY. 679 



of the sea; the line of separation, the record of a long time when the 

 region was dry land. The events in the history of this intervening 

 time, the period of dry land, one might suppose were all lost. What 

 plants lived here, we cannot learn ; what animals roamed over the 

 hills, we know not ; and yet there is a history which is not lost, for 

 we find that after these beds were formed as sediments beneath the 

 sea, and still after they had been folded, and the sea had left them, 

 and the rains had fallen on the country long enough to carry out 

 10,000 feet of rocks, the extension of these beds to the south, which 

 were cut away, and yet before the overlying Carboniferous rocks were 

 formed as sediments of sand and triturated coral-reefs, and ground 

 shells and pulverized bones, some interesting events occurred, the 

 records of which are well preserved. This region of country was 

 fissured, and the rocks displaced so as to form faults, and through the 

 fissures floods of lava were poured, which, on cooling, formed beds of 

 trap or greenstone. This greenstone was doubtless poured out on the 

 dry land, for it bears evidence of being eroded by rains and streams 

 prior to the deposition of the overlying rocks. 



Let us go down again, and examine the junction between these red 

 rocks, with their intrusive dikes and overlying beds of greenstone, 

 and the crystalline schists below. 



We find these lower rocks to be composed chiefly of metamor- 

 phosed sandstones and shales, which have been folded so many times, 

 squeezed, and heated, that their original structure, as sandstones and 

 shales, is greatly obscured, or entirely destroyed, so that they are 

 called metamorphic crystalline schists. 



Dame Nature kneaded this batch of dough very thoroughly. After 

 these beds were deposited, after they were folded, and still after they 

 were deeply eroded, they were fractured, and through the fissures 

 came floods of molten granite, which now stands in dikes, or lies in 

 beds, and the metamorphosed sandstones and shales, and the beds of 

 granite, present evidences of erosion subsequent to the periods just 

 mentioned, yet antecedent to the deposition of the non-conformable 

 sandstones. 



Here, then, we have evidences of another and more ancient period 

 of erosion, or dry land. Three times has this gi-eat region been left 

 hio-h and dry by the ever-shifting sea; three times have the rocks 

 been fractured and faulted ; three times have floods of lava been 

 poured up through the crevices ; and three times have the clouds gath- 

 ered over the rocks, and carved out valleys with their storms. The 

 first time was after the deposition of the schists; the second was after 

 the deposition of the red sandstones ; the third time is the present 

 time. The plateaus and mountains of the first and second periods 

 have been destroyed or buried; their eventful history is lost; the 

 rivers that ran into the sea are dead, and their waters are now rolling 

 as tides, or coursing in other channels. Were there canons then ? I 



