THE OLD AGE OF CONTINENTS. 129 



plateau " of the continent, formed of the vast stony sheets, 

 piled one above the other, which have never been tilted 

 from their approximate horizontality since the beginning 

 of Palaeozoic time. And here, again, we are led to inquire: 

 Whence so vast an amount of sedimentary material, strewed 

 through Palaeozoic, Mesozoic, and Tertiary ages, over the 

 bottom of that broad continental ocean? Whei-e now those 

 wide-extended lands or towering mountain ridges whose 

 dissolving substance yielded sand and cement for the Ti- 

 tanic masonry of a new-made continent?* Wherever it 

 was, and whatever it was, the " tooth of time " has gnawed 

 it to a skeleton. It is a continent of the past, worn out by 

 the uses to which nature has subjected every continental 

 area in turn, and which to-day are wearing out and de- 

 stroying the land on which, for the passing time, the hu- 

 man race, like those which have preceded it, has found 

 a momentary foothold. 



But the great central plateau, once freshly formed from 

 the older lands which were exhausted in its formation, is 

 in turn but the ruins of a former fruitful and smiling 

 region. For nearly a thousand miles in breadth, and 

 probably two thousand miles in length, stretching from 

 the Mormon monarchy southward far into the republic 

 of Mexico, a frightful desert reigns. Naked rocks and 



compiled under the direction of Dr. F. V. Hayden, and the accompanying text; 

 also Capt. C. E. Button's Geology of the High Plateaus of Utah, prepared under 

 the direction of Maj. J. W. Powell. 



* Mr. Clarence King, in his Survey along the fortieth Parallel, has shown 

 that a great western continent existed during Palaeozoic time in the western 

 portion of the Great Basin or present Nevada plateau, which was mostly sub- 

 merged at the end of Carboniferous time. By the end of Jurassic time, the Sierra 

 Nevada and Basin Ranges to the east had become uplifted. At the end of the 

 Cretaceous, the Uinta and Wahsatch ranges appeared, together with some new 

 portions of the RocKy Mountains. It is probable that the denudation of these 

 regions supplied a large part of the sediments which went to build up the vast 

 plateau regions in Colorado and Utah. 



