46 The American Geologist. July - 1903 - 
side of Fourth Street, reached bed rock only at a depth of 125 
feet. West of this a second shaft ( now filled up) was sunk in 
1870, near the corner of Rose and Third Streets in George- 
town, where the surface is approximately fifty feet lower (the 
first shaft starting on the detrital cone originating in Leaven- 
worth gulch), and not more than 150 feet from the steep base 
of Leavenworth Mountain, reaching bed rock at a depth of 
seventy-five feet. Half a mile to the northward, and close 
against the base of Griffith mountain, near the mouth of the 
lower tunnel, a shaft reached bed rock at 60 feet ; and a short 
distance north of this, near the present base of the high clump 
of the main Griffith tunnel, and possibly not over 100 feet from 
the base of the mountain, a well was sunk in early days to a 
depth of about 100 feet without reaching bed rock. 
In view of these facts, it can hardly be doubted that the part 
of the valley occupied by Georgetown is a depressed fault 
block, or graben, and that the valley is due in part to displace- 
ment and not wholly to erosion, thus suggesting comparison 
with Yosemite valley. This view calls for another and comple- 
mentary fault along the west side of the valley, at the base of 
Republican mountain, and of its existence we have ample evi- 
dence, although in this instance the displacement is not close 
against the mountain. The confluence of the two creeks is not 
near the foot of Leavenworth mountain, as would be most nor- 
mal, but half a mile or more to the northward ; and as a spec- 
ially interesting and puzzling feature in the topography of 
Georgetown we have the narrow ridge of granite extending 
north from the northwestern corner, or spur, of Leavenworth, 
separating Clear creek from the level plain on which the main 
part of the town is built and terminating abruptly in the bold 
knob on which formerly stood the brick stack of Hall's reduc- 
tion works. This knob or ledge is the point of view for Figure 
3, which shows the ridge of granite bordered by the bed of 
Clear creek on the right and connecting upward on the left with 
the angle of Leavenworth mountain. On the west side of this 
ridge, which at the lowest points is not more than five feet 
above the creek, the latter actually or practically flows in the 
bed rock surface, while on the east side the level gravel floor of 
the valley is ten to twelve feet, and the bed rock floor eighty- 
five or ninety feet, below the level of the creek. Obviously the 
