130 SPAEKS FROM A GEOLOGIST'S HAMMER. 



thirsty sands, and shrubless, treeless wastes are only di- 

 versified by yawning chasms and dismal cafions and Cy- 

 clopean walls rising in the distance from height to height, 

 like the gigantic steps by which the monster Typhon 

 scaled the realm of Jove. Once on a time a thousand 

 mountain streams leaped down upon this plain, and gath- 

 ered themselves by degrees together, and grew into the 

 majestic Colorado, which glided quietly, or by occasional 

 falls, into the gulf of California, itself now shrunken to 

 half its former dimensions. At intervals, expanded crys- 

 tal lakes, turning their mirror surface toward the sun as 

 cheerfully as ever smiled Lake George. The incumbent 

 atmosphere drank copiously from the abundant waters, 

 and returned its deluges of thanks in cooling summer 

 showers. Thus herb and shrub and forest tree rejoiced, 

 alternately, in smiling sunlight and refreshing rain. The 

 great central plateau was the prairie region of the con- 

 tinent. It was this, perhaps, while the region east of the 

 Mississippi was lying a worn-out desert waste, unreno- 

 vated since the age which witnessed the elevation of the 

 Alleghanies. But the ceaseless erosion of running streams, 

 for thousands of years unnumbered, has sunken the water- 

 courses of the central plateau to the depths of hundreds 

 and thousands of feet ; every lake is drained ; the local 

 supply of moisture has disappeared ; the streams have 

 withered in their ancient channels ; vegetation has re- 

 treated to the mountain slopes; the giant Cereus alone 

 rears its specter form like a ghostly visitant to the graves 

 of its former kindred. 



There is reason to believe that before the advent of 

 the glacier epoch nearly the whole of North America was 

 a worn-out continent. It is possible, however, that most 



