288 GEOLOGY OF THE BLACK HILLS. 



the West, but this is the first instance that has come under my personal 

 observation. 



Descending the ravine about half a mile traces of previous explorers 

 were found. Several prospecting holes had been sunk near the stream 

 and considerable work done in the vicinity, probably by a small party of 

 miners early in the preceding spring, as small aspen trees which they had 

 cut down in clearing the ground for working showed half-grown leaves 

 dead and shriveled, but still clinging to the twigs. A number of these old 

 prospecting pits were bailed out, the gravel obtained from off bed-rock, and 

 tested by panning. But in no case did we find gold in paying- quantities ; 

 half a cent to the pan being the highest result of the trials. It is probable 

 that the miners who dug these holes obtained discouraging prospects, or 

 they would not have abandoned the district without making it known. 



Exploring a number of small streams rising near Warren Peaks, flow- 

 ing to the north and east, gold was found in gravel deposits in the flats 

 along the banks of the creeks in several places, but nowhere in paying 

 quantities, though from want of time we were unable to thoroughly test 

 all the different ravines in this district. The cluster of hills of igneous 

 rocks which have yielded the gold are but four to five miles across. The 

 gravel deposits formed by the creeks extend, however, for some distance 

 down the valleys, beyond the outcrop of the Potsdam, and are found rest- 

 ing on limestone bed-rock, so that the district is really elliptical in area and 

 six to eight miles in diameter, covering an area of from forty to fifty square 

 miles. The streams being small and' the wash not very great, there were 

 no high -gravel deposits, though one or two bars covering about an acre 

 were observed occupying flats elevated 3 or 4 feet above the creek. 

 The gravel was 2 to 5 feet deep, composed wholly of feldspar and the soft 

 plastic clay resulting from its decomposition, intermixed with considerable 

 iron and manganese pebbles derived from the ledges. The valleys of the 

 creeks are not deep, but are narrow, contracted, and overgrown with 

 thickets of willow, so that only at intervals are gravel flats of any consid- 

 erable size found along their course. The most extensive of these bars 

 were found near the outcrop of the limestone, the bed-rock being soft cal- 

 careous sandstone of the Carboniferous age. These deposits were situated 



