DENVER & RIO GRANDE WESTERN ROUTE. oe7 
region is known as the Great Basin, a land of desert basins and of 
barren mountain ranges, which in general trend north and south. 
The precipitation here is slight, ranging in this latitude from 5 to 8 
inches, and that which falls finds its way into some deep basin in the 
interior like Great Salt Lake, where the water, when it evaporates, 
leaves the mineral matter that is carried in solution to form beds of 
salt or soda. 
The walls of the canyon, although steep, are generally smooth 
and are covered, except in the higher parts, by brush and dwarf trees 
of many kinds. In summer they are clothed in a soft, beautiful 
green, with here and there an evergreen tree to accentuate the soft- 
ness of the foliage of the other trees, but in September, after the 
frost has touched the dwarf maples of the higher slopes, the color- 
ing is magnificent. Many of the slopes are a blaze of scarlet from 
top to bottom, and others show scarlet interspersed with brown and 
green. The clumps of aspen give the landscape a touch of gold, and 
the whole scene presents an unexcelled splendor of autumn colors. 
The canyon grows broader to the west, and the railroad is built 
along its north wall. On the opposite side, near milepost 687, is the 
headgate where the water of Spanish Fork, including that from 
Strawberry River, is diverted into a large canal, which is soon lost 
to view as it follows the south wall of the canyon to the mouth and 
there turns to the left to the area where its waters are most needed. 
The outlet of the canyon is not like the outlets of most of the can- 
yons that the traveler has seen but seems to be dammed or choked by 
a great mass of gravel. Where first seen, a little below the intake 
of the canal, the gravel is at railroad level, and its top is flat, as if 
it had been washed down the canyon and deposited as a delta in stand- 
ing water. An examination of the opposite slope shows a terrace of 
similar material about 100 feet higher. This terrace also appears 
to have had a similar history, except that as it is the older of the two 
deposits most of its gravel was washed away when the second ter- 
race was formed, and so only fragments remain where they have been 
protected on the side slopes. These terraces are of the greatest sig- 
nificance in the interpretation of the late geologic history of this 
region; to the geologist they have much the same value that the cliff 
dwellings or tables of cuneiform writing have to the archeologist. 
They constitute the record of one of the most remarkable geologic 
events in this country—the flooding of the basin of Great Salt Lake 
during the ice age to a depth of more than a thousand feet. When 
these terraces in the Spanish Fork canyon were formed the water 
of Lake Bonneville, as it has been called to distinguish it from the 
present lake, entered the mouth of the canyon at the level of the 
highest terrace, and if a traveler had then attempted to make a west- 
ward journey here he would have been confronted by an inland fresh- 
