TIIK 01,l)i;i; MKSOZOK" OF AIM/OXA. 2o 



posed to form scvcM'al quite distiiicl sulidh isions. Indeed, 1 \v;is of 

 this opinion dui'in.ii:; most of my s1;iy in tlic lower I/iltle Coloi'ado Valley, 

 but (>\'en hefoi'e lea\'ino; Ihei'e the proofs of their hoinou'eneit y had 

 heeome appai'eni . 



At l(>ast tli(> lower half eonsists of those remai'kahhOx'ds in which 

 1 had rrriiiinally found the vc'lehrate bones in IS!)',), and in which .alone 

 thus fai' \'ei'tebrate remains ha\'e been obser\-e(l. 1 lia\(' sometimes desifr- 

 nated ihem the variegated m.ai'ls and sometimes the Belodon beds. 

 The distinguisliing feature of these beds is the jnvsence of '^ivdi num- 

 bers of small buttes, the smaller one.s appearing to be blue clay knolls, 

 l)U( the lai-g(M' ones showing other colors, especially purple, and some- 

 times several bantls of different hues. Almost (>\erywhere at this horizon 

 there exist plains, dotted .all over with tliese remarkable httle buttes, 

 varying from '.] or 4 feet to 20 or 3U feet in height, usually i.solated from 

 one another and luiA'ing a form peculiar to them. They are not conical 

 in the true sense of the word, since they do not rise to a point at the 

 summit, but are always rounded off and have the form of a well-made 

 haystack, the smaller ones looking like haycocks in a field. These 

 butte-studded plains are of course simply the remains of a plateau or 

 mesa which has been worn away, primarily by the action of water, 

 but for a very long period there can be no doubt that wind has been 

 the more potent agency. There is evidence throughout that entire 

 region that the amount of precipitation was formerly much greater 

 than at present, and in so speaking I do not refer to a very remote date 

 geologically, l)ut to a period which was probably post-Tertiary. Indeed, 

 from the present condition of many of the regions in which we know 

 that the early Indians dwelt and which are now perfectly dry, with 

 all sources of water so remote that they can no longer be inhabited, 

 it must l)e inferred that there has been a change in the climate within 

 the period of human occupancy. Certain it is that water is doing very 

 little relatively in this region now, while the agency of wind is conspic- 

 uously marked wherever it can produce elTects. The peculiar form 

 of these buttes is not such as water could have produced, while it is 

 precisely the form that wintl would naturally produce, acting upon 

 the \-ery fine and soft materials, somewhat resembling ashes, that com- 

 pose these Ijuttes. 



