GOLD 707 



W. of K. and E. of S. The extent of the diluvial deposits is commensurate, or 

 nearly so, with that of the gold-bearing region, in that part of the country which ho 

 has examined. They are found in a belt of land from thirty to sixty miles broad, 

 and running parallel with the axis of the range ; and, from facts that he has ascer- 

 tained from others, he states that ho has no doubt but that they exist throughout all 

 the gold-bearing region, both north and south. These diluvial deposits are met with 

 as we advance towards the lower hills of the Sierra, extending frequently some miles 

 into the plain. On ascending from the lower hills towards the mountains, the diluvial 

 bods no longer occupy the same relative position : occasionally deposits of rounded 

 stones can be found in the valleys and on the sides of the hills, but when this is tho 

 case, their origin can always be traced to deposits existing on the tops of the sur- 

 rounding hills, from which 'they have been brought down by the action of the causes 

 now at work. As we ascend towards the axis of the chain, these deposits become 

 more extensive, and at a distance of twenty or thirty miles from the lower hills, they 

 are found occupying the crests of almost all the highest ridges in the country ; but 

 besides being found on the crests of the ridges, where their extent frequently does 

 not exceed a few yards in breadth, they are also met with covering the extensive 

 elevated flats which exist on the benches between the different watercourses, forming 

 continuous beds of some miles in extent, which are rarely interrupted by the pro- 

 trusion of any of the older rocks. Where found in elevated positions, the lower hills 

 and valleys are entirely free from them ; frequently a large section of the country 

 will be enclosed with two high ridges capped by deposits, and diverging from a 

 common point ; in the intervening space will be seen many secondary ridges, some- 

 times fifteen or eighteen hundred feet high, formed entirely of the older rocks, no 

 traces of deposits being found on their surface, nor in the ravines that lead from 

 them. 



The depth of these deposits is extremely variable. Sometimes nothing more than 

 a trace of them in the presence of a few round pebbles lying on the top of a ridge is 

 found; -the valleys and ravines in the neighbourhood containing their disintegrated 

 elements in considerable quantities. In other instances, particularly where spread 

 out over the elevated flats, they are of a moderate and pretty uniform thickness for a 

 considerable distance, varying from two to three feet to a few inches, and this, too, 

 in positions where the surface could not have been exposed to any great amount of 

 denudation. They are again found many hundred feet in thickness, composed of 

 superimposed strata of different mineralogical constitution, generally horizontal and 

 conformable with each other. 



The localities where the deposits are met with most extensively disclosed, and that 

 have been worked, are at Nevada and at Mokelumne hill. At the former place they 

 form the crest of a high mountain, called the Sugar-loaf, full 2,000 feet above the 

 level of Deer Creek, the upper 600 feet being formed entirely of diluvial strata. At 

 Mokelumne hill they are also 200 feet deep, forming here also the summit of' a high 

 and isolated mountain. The elements of which they are composed diifer considerably 

 in different localities, although there are through the whole series many points of 

 resemblance. In the lower valleys and flats between the ranges of the lower hills, 

 they appear to consist of beds of gravel, containing occasional boulders of quartz and 

 the harder rocks. On the elevated flats higher up in the mountains, the surface of 

 these deposits is generally covered by a reddish loam, mixed with small gravel ; 

 whilst reposing on the bed-rock, and a few inches above it, is found a stratum con- 

 taining large boulders and gravel, the boulders being principally quartz. On the 

 tops of the hills and the crests of the ridges, where they generally attain their greatest 

 thickness, we find them composed of many distinct strata lying nearly horizontal and 

 conformable with each other, and generally also with the surface of the underlying 

 rocks. In these situations the most superficial stratum is composed of a mass of 

 extremely hard conglomerate, containing principally trachytic rocks, imbedded in a 

 hard argillaceous cement. It is this hard stratum that has undoubtedly preserved 

 tho underlying beds from the destructive influence which has so powerfully acted on 

 the surrounding rocks. 



At other points the whole series consists of conglomerates and soft friable sandstone. 

 In the lower strata quartzose conglomerates, with an argillaceous cement, or loose 

 quartzose gravel, always prevail, with large boulders of quartz, weighing frequently 

 two or three tons, haying their surface worn smooth and the angles rounded. The 

 deposits of the heavier rocks have been formed on spots which were evidently lower 

 than the level of the surrounding rocks ; whilst on those parts which were higher at 

 the time the deposits were formed, tho higher trachytic rocks are found. As far as 

 Professor Blake's researches have extended, the more quartzose conglomerates have 

 been invariably found on the erupted rocks, whilst the stratified rocks which they 

 had upheaved were only covered by the trachytic conglomerates. The pebbles of 



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