CIRCLE PRECINCT. 193 
hat there are considerable areas of unfrozen ground. There is no 
neasure of the thickness of the alluvium below a point one-half mile 
Jbove the mouth of the valley, where it was only 10 feet to bed rock, 
lowever, it does not seem probable that the bed-rock floor slopes more 
han 25 feet to the mile, and, therefore, it is not to be expected that 
he alluvium will be found to be more than 35 feet thick. 
Among other improvements which will undoubtedly come is the 
working of large groups of claims instead of individual holdings, 
mere is no doubt that if the entire creek could be worked by one com- 
>any there would be a great economy in costs and a greater percent- 
ge of the values could be recovered. There appears to be little 
ope of obtaining water outside of the basin, but the creek itself fur- 
tishes an adequate supply in most seasons for at least one large 
peration. 
The gold output for 1906 is estimated to have been about $120,000 
value, less than 50 per cent of which was taken out by winter 
rifting. It is estimated that 11 claims were worked during the 
inter by 35 men and 13 claims during the summer by 60 men. 
BOULDER CREEK. 
Though the gravels of Boulder Creek are auriferous, as would be 
xpected, for it lies in the gold-bearing zone, yet so far the only 
lacer values found have been on a small tributary called Greenhorn 
'reek. Here the gravels are only 4 feet deep, but although they 
arry good values, the lack of water often prevents mining during 
mch of the open season. 
MAMMOTH CREEK. 
Mammoth Creek, which is formed by the junction of Independence 
nd Mastodon creeks, has a broad flood plain, being 100 to 500 yards 
ride. The bed rock is probably chiefly schist, but in part granite, 
fhe granite yields some large bowlders; the schist is as a rule deeply 
ecomposed. The bed-rock floor slopes at a very low angle. The 
piuvium is probably 10 to 15 feet deep, and is made up of rather well- 
bunded material, much of which is frozen. In the excavations, 
pwlders of 2 to 2\ feet are not uncommon, and some 3 to 4 feet in 
iameter were observed. The gold is reported to be fine and its dis- 
tribution fairly uniform. Mammoth Creek has not been the scene 
If much mining except at its head and about halfway to its mouth. 
Lt the latter place a small steam shovel was installed and a pit of about 
,000 cubic yards capacity excavated some years ago. This was an 
xperiment and the results are said to have been satisfactory to the 
perators. In 1906 the creek was under examination by dredging 
,ien, who seem to be justified in considering this dredging ground. 
Bull. 314—07 13 
