10 GEOGRAPHY AND GEOLOGY OF RAMPART REGION. 
topographic detail. The edges of upturned limestone beds have been reduced by 
weathering to more or less disconnected, precipitous, shattered masses which rise in 
places to heights of several hundred feet above the general outline and impart to the 
range a peculiarity of form almost as striking as that of color. The rocky slopes are 
made less precipitous by the piles of debris into which they plunge, and these in 
turn run out into a gradually sloping more or less extensive base covered with the 
vegetation of the tundra and flattening until it merges with slight abruptness into 
the valley of Beaver Creek. The rocky slopes above are furrowed with steep rock- 
strewn gulches which are mostly dry. In the lower part these gulches become nar- 
row valleys inconspicuously sunk in the surface and carrying ordinarily but little 
water. 
Southwest of the White Mountains, across Beaver Valley, bare even-topped ridges, 
nearly uniform in height, form the background of the amphitheatral area around 
the bend of Beaver Creek and extend northward to become laterally adjacent on the 
west to the terminating ridge of the White Mountains. A few jagged points project 
inconspicuously from the level of these ridges and seem to indicate the continuation 
in this direction of the formations so accentuated to the northeast and to emphasize 
the loss of topographic individuality that has been sustained. A few miles west of 
the southern part of the mountains the country opens widely toward the southwest, 
where a broad low divide, with an altitude of approximately 1,500 feet, separates 
the Beaver waters from streams tributary to the Tanana. 
Northwest of the White Mountains, between Beaver Creek and Yukon Flats, 
in a distance of about 20 miles, there are several nearly parallel ridges, the trend of 
which is at first northeast parallel with the White Mountains, but changes gradually 
as t hey are crossed from one to the other northward until the trend of the ridges 
near the Flats is approximately east and west. The ridges are of various heights, 
with an average of perhaps 2,500 feet, and have a somewhat uneven outline. Between 
the steep-sided prominent ridge which forms the northern limit of Beaver Val- 
ley and the equally prominent ridge which overlooks the Flats there is the divide 
which separates the headwaters and tributaries of three important streams — Beaver 
Creek, Hess Creek, and Tolovana River. This divide, in comparison with the ridges 
which start from it and gain in prominence down their respective drainage systems, 
is low and inconspicuous and shows an area of open country where long, bare, gradual 
slopes present the clean-cut appearance of meadows freshly mown (PI. II, i?). The 
drainage is marked by lines of green traced along the flatly intersecting bases of the 
slopes, vivid in color toward the sources of the streams where only willow patches 
grow and of a more somber shade lower down the valleys where scattering groups 
and lines of spruce are delicately outlined against the brownish background. 
Northward the country rises gradually to the level of an even-topped east-west 
ridge 2,000 feet in height, surmounted by a few steep-sided domes of greater height, 
and then descends by intermediate flanking ridges with more or less abruptness to 
the Flats. The northern and southern slopes of this ridge are deeply cut by minor 
tributaries and toward the west it terminates finally as a spur between Hess Creek 
and one of its^ northern tributaries. The flanking ridges on the north replace it and, 
with approximately the same altitude, continue westward toward the Yukon at Fort 
Hamlin. 
The main divide between the Yukon and Tanana drainage systems is about 25 
miles south of the Yukon and extends in a nearly westerly direction toward the hills 
of Rampart. There are no topographic features of special interest. The divide is in 
places a well-defined ridge sharply differentiated from its surroundings; at other 
localities it is less conspicuous than the numerous long lateral spurs which descend 
irregularly from it toward the valleys of Hess Creek and Tolovana River, and at one 
locality, as far as could be observed, the headwater streams from the north and south 
