GEOLOGICAL KEPOltT. 321 



A plentiful affluent will mostly furnish good water, unless the strata which it percolates 

 are charged with much salt. 



We will very seldom obtain favorable results by dimmer at other points. I have 

 frequently mentioned the reservoirs of water, formed by the absorbent deposits, at the 

 bottom of many valleys, but to strike them, even from the lowest points of the vallev, 

 wells would generally attain such a depth as would make them almost useless, and the 

 water would frequently be salt. Besides, we could onlv distantlv guess at the con- 

 figuration and greatest depressions of the rocky base, and. consequent! v, the most 

 favorable location for the wells. In order to save time and monev, we would in such 

 cases recommend at least a previous examination by means of an earth-borer. 



SOIL AND VEGETATIOX. 



From what has been said above, in speaking of the valleys in general, it appears 

 that arenaceous material constitutes a considerable portion of the soil" more or less 

 mixed with clay. Where the former prevails, the soil naturally becomes unfit to sus- 

 tain any vegetation except a peculiar desert growth : but the more it is mixed with 

 argillaceous material, and the detritus of other rocks, the more nutriment it can afford 

 to the plants. The igneous rocks, by their decomposition, add considerably to the 

 fertilizing ingredients. 



From this it would appear that a large portion of the soils must be well consti- 

 tuted for productiveness. There are, however, other causes which generally prevent 

 the spontaneous growth of such a vegetation as we find in more favored countries, and 

 confine the successfully cultivable ;ireas to exceedingly narrow limits. These are 

 chiefly to be found in the meteorological condition of the country. In some narrow 

 mountain-gorges, where there is abundance of moisture, we find a quite luxuriant 

 vegetation ; but wherever the country opens out, it assumes the character of barrens 

 and deserts. The growth of the valleys consists mostly of several species of Artimisia 

 (sage) and allied plants, becoming more and more dwarfish, and assuming a more 

 sterile character, where the soil is more sandy and poor. In spots which receive mois- 

 ture only periodically, and have a stiff, clay soil, greasewood is the prevailing vegeta- 

 tion. Places which are subject to overflows, and kept moist during the greater part of 

 the year,, favor the growth of wire-grass, and other coarse swamp-grasses; more 

 mountainous localities of this kind are covered with meadows of a tall grass resembling 

 somewhat rye. At still more swampy points, rushes and sedge-grasses occupy the 

 surface. Over dry, deep sandy slopes, an exceedingly nutritious grass is scattered in 

 single bunches, bearing large sweet seeds, which arc eagerly sought for by animals 

 and Indians. For the latter, most of the grass-seeds constitute a main portion of their 

 winter supplies. In most of the mountain-ranges, several species of the so-called 

 mountain-grasses abound. They are highly nutritious, and come out very early in 

 spring ; and even in midwinter, after a few warm days, young green sprouts may 

 be seen between the matted bunches of last year's growth. Being of a rather dry 

 texture, they retain their nutritious qualities as fodder, in these arid regions, all the 

 year round, and it is principally on them that the cattle subsist. 



The growth of timber is confined to the mountain-ranges and some broken sandy 



