58 
GUIDEBOOK OF THE WESTERN UNITED STATES. 
worked out, but it was doubtless caused by glaciers which crossed 
souri River and extended to the southwest as far as this valley, 
damming the streams and compelling them to find new outlets. 
Hebron, one of the new towns of western North Dakota, is the 
center of a prosperous agricultural district and is noted for the 
manufacture of fire and pressed brick, the clay for 
Hebron. 
aimed 2,180 feet. 
pooner 
Paul ae wifes. 
which is derived from the Fort 
The bed of clay utilized is at least 50 feet. thick. 
Beyond Hebron the railway follows the broad, open 
Union formation. 
valley of Knife River to its head, where there is a 
steep climb to the summit of the dividing ridge between that stream 
Heart River on the southwest. 
point is reached a short distance beyond Antelope, 
where a good view can be obtained of the upland 
Antelope. 
Elevation 2,435 feet. 
St. Paul 531 miles 
e highest 
surface of this part of North Dakota. The surface 
is gently undulating, but here and there on the principal divides 
knob 
there is a hig 
general a 
that has not been reduced by erosion to the 
The sides of these knobs are generally bare, and they 
have been sculptured by the rain, the frost, and the wind into most 
beautiful and intricate forms. 
(See Pl. V, 
p- 53.) 
of Chinaand Japan. The ginkgo has had 
in many ways a more wonderful geologic 
history than any other tree now living, as 
it has come down to us practically un- 
N 
. 
FIGURE 6.—Ginkgo leaf. 
changed from earliest Mesozoic time. It 
apparently saw its — during what is 
known as the Jurassi: see table on 
p. 2), when it eaahiy spread from the 
Arctic regions over most of the globe, but 
since that time it has been gradually 
dwindling until it is now represented bya 
single living species in Japan and China. 
It is regarded as a sacred tree in the Far 
East and as such is planted about the tem- 
ples and sanctuaries, but there is great 
doubt as to its existence in a truly wild 
state. It is not likely to become extinct, 
however, for its fascinating history and 
curious fernlike foliage (see fig. 6) have 
made it of eae d thint 44 ton Aan 
extensively planted in many parts of the 
tree on the streets of Washington, D. C 
Among the so-called higher flowering 
plants there were many grass and sedge- 
like plants during Fort Union time, but 
none that were very conspicuous or other- 
which once grew along the lower reaches 
of Yellowstone River in Montana, as 
shown on Plate XI, B (p. 75) 
The plants with deciduous leaves (dico- 
tyledons) flourished in great numbers in 
Fort Union time, as they do now. They 
