16 SUEVEY OF COLOEADO AND NEW MEXICO. 



masses of granite of all kinds, but slightly worn ; but proceeding from 

 the base of the mountains, the rocks become smaller and more rounded, 

 until they pass into small pebbles, mingled with loose sand. 



The phenomena of erosion, as seen at the present time, all along the 

 flanks of the mountains, in the x)lains, in the channels of streams, point 

 clearly to a vastly gxeater quantity and force of water than exist any- 

 where at the present time. 



The surface of the country along the base of the mountains is ex: 

 tremely undulating — worn into hill, valley, ridge, or rounded buttes. 

 The strata in these ridges and hills show that the entire surface was 

 much higher than it is at present, and that these ridges and buttes are 

 only remnants of beds left after the erosion, and how great a thickness of 

 strata was originally deposited above these remnants, and is now en- 

 tirely swept away, it is imjDossible to determine, though we believe it 

 was very great. 



E'ow, on these hills are the greatest numbers of large, rounded stones, 

 of all kinds, granite and sedimentary, as if they had been left there by 

 the melting masses of ice which had lodged on the hills. .These stones 

 are also accumulated in long lines or belts, as if they had been driven by 

 currents so as to form shore liues, or lodged-in eddies. The evidence is 

 clear that great bodies of water, in which were probably mingled masses 

 of ice, swept over the i)lain country within a comparatively recent 

 geological period. 



Opposite Camp Carling, in the bluffs of Crow Creek, a good thickness 

 of drift is seen filling up the irregular surface of the modern tertiary 

 beds, so that we have evidence of quite extensive erosion of the surface 

 prior to the deposition of this drift. 



Along all the main water-coiu'ses are high ridges showing the rocky 

 strata perfectly. A little lower is a second ridge, mostly grassed over, 

 but more or less parallel with the higher ridge ; then we have a gradu- 

 ated series of terraces, from one to three, extending down to the water's 

 edge. This description applies to all the main water-courses along the 

 base of the mountains, whether there is running water in them at this 

 time or not ; and they all seem to give evidence that the^'^ once contained 

 far more water than at present. This configuration of the surface aids 

 much in giving a sort of picturesque appearance to the x)lains, inasmuch 

 as we cross these undulations at right angles in traveling north to 

 south. 



The soil in the valleys of the streams is rich enough, and when it can 

 be irrigated, will produce good crops ; and not until the farmers and 

 stock-growers begin to settle about Cheyenne will it have a loermanent 

 and substantial growth. 



June 30. The distance from Cheyenne to Laporte, on the Cache la 

 Poudre, is forty miles. The tertiary pudding-stone beds extend along 

 the immediate flanks of the mountains for twenty-five miles, but disap- 

 pear from the plains within ten or fifteen miles of Laporte. 



I have estimated their entire thickness here at from twelve hundred 

 to fifteen hundred feet. The high hills near the station are capped with 

 coarse sandstone, with horizontal strata, and are eight hundred feet 

 above the bed of the creek that flows near th(;ir base. From beneath 

 these recent beds arise the more sombre-hued beds of the lignite tertiary. 

 We have then broad grassy plains, dotted here and there with buttes 

 like truncated cones, and long narrow belts of table-lands, with perfectly 

 plain surfaces to the eye, from a distance. Why these more modern 

 tertiary beds are so persistent along the immediate sides of the moun- 

 tain, but have been entirely swept away ten miles to the eastward, I can- 



