6 GO IDAHO MINING DISTRICTS. 



three most impressive topographic features are (1) the broad valley; 

 (2) the level ridges between Idaho City and Centerville, between Elk 

 Creek and Moore Creek, and between Granite and Bannock gulches, 

 rising to an elevation of 1,000 feet above the valley; and (3) the 

 encircling rim of high, deeply dissected peaks and ridges, attaining 

 a height of 2,000 or 3,000 feet above the valley. 



The present stream gravels. The alluvial gravels filling the bed 

 of the present stream form broad flats, over which the water course 

 meander's in changing channels. The largest part of these gravels is 

 debris from the hydraulic mining operations carried on in the bench 

 gravels and the high gravels. The width of the tailings below Idaho 

 City reaches 1,000 feet. In two places the channel contracts between 

 low, projecting hills. At Idaho City the maximum width is reached; 

 here the tailings are about 2,000 feet wide, contracting again to a nar- 

 row channel 1 miles above the city. Two and one-half miles above 

 the same place a comparatively narrow canyon begins, and the tail- 

 ings are only up to 200 feet wide. The tailings cover the imperfectly 

 washed original creek bed, and in many places also the first (lowest) 

 terrace or bench. At Warm Springs they are reported to be 15 feet 

 deep; at Idaho City as much as 40 feet. They consist chiefly of 

 granitic and porphyritic pebbles, with much sand. By a natural proc- 

 ess the gold in the tailings is gradually concentrated. At some time 

 the whole creek bed will probably be washed over again to recover 

 this gold and to reach the older bottom gravels, which are supposed 

 to be rich in many places. Probably the only way in which this can 

 be profitably done is by means of hydraulic elevators or dredges. 



The stream gravels were most extensively worked in early days. 

 Moore Creek was very rich up to the mouth of Gambrinus Gulch, 

 though gravels have been washed still higher up. The gulches enter- 

 ing from the south, as a rule, paid only for a short distance from 

 the main creek; their upper courses were nearly barren. On the 

 northern side, Gambrinus and Illinois gulches were extremely rich. 

 Bear Gulch has also been worked extensively. The bottom of Elk 

 Creek in its upper course is generally narrow, but was rich up to 

 Boulder mine; 2 miles below Boulder mine the creek bottom widens 

 to 200 feet, and placer diggings were being operated in 1896. Deer 

 Creek, heading at Summit mine, yielded very heavily, the output of 

 the half mile near the summit being placed at $90,000. Wolf Creek 

 has been worked, but was not so rich. Spanish Creek was also 

 worked, and near its head lies a flat, one-eighth mile wide and one- 

 half mile long, covered by 12 feet of angular wash, which has been 

 extensively worked, the gold being probably derived from small 

 seams or from a gold-quartz vein not yet discovered. 



The gulches entering from the north and south below Idaho City 

 were generally barren beyond the extent of the terraces. 



Bench gravels. Where the broad valley opens, 6 miles below Idaho 



