34 GUIDEBOOK OF THE WESTERN UNITED STATES. 
The silt deposited in this lake gives the valley its wonderfully smooth 
surface and its great fertility. During the highest stage of the lake 
Buffalo Creek built just below Muskoda a delta of considerable size, 
and it is from this delta that the first view of the valley may be ob- 
tained. At a later stage, when the water of the lake was at a lower 
level, the waves cut away the front of the delta and greatly increased 
the natural slope of the valley side, as shown in figure 4. The rail- 
way engineers found difficulty in getting down this slope without 
loops and curves, so a long, high fill has been made which gives a 
uniform grade from top to bottom.! The weight of the fill, however, 
proved to be too great for the soft mud at the bottom of the old 
A_. Lake Agassiz ___ B YY 
ee UMA 
5 UW i YY, 
-- JUL AN GHALELPELL 
es) 
LLL 
GUMS Spl Ee® 
SELL WUE 
FigurE 4.—Section of Buffalo River delta, Minn. AB, Surface of Lake Agassiz at the Herman stage; 
EFB, delta profile; CD, level of water at Campbell stage; EDF, part of delta cut away by the waves, 
leaving the steep westward front (DF). 
lake bed, and it is still settling and throwing up a-ridge of the soft 
material on each side. 
From the high fill the traveler can see something of the great 
extent of the valley—its level floor stretching mile after mile without 
the least eminence or depression to break its regularity—and some 
of the fine farms that have made it famous. Drilling for water has 
shown that originally the surface of the valley was uneven, much 
like the country on both sides. At a later date the valley was filled 
by a great glacier that came down from the north, grinding and 
scouring away many of the projections and filling the depressions with 
the waste material; and then as the last smoothing process the fine 
mud carried by the streams settled in the lake, giving the valley its 
present smooth surface. 
‘In the original construction of the | the original grades at man 
Northern Pacific Railway the standard volving a 1 
maximum grade adopted was 52 feet to 
the mile except on the mountain sec- 
was found necessary, for economy of | of these reductions of grade. 
except upon the mountain sections. tive. Man 
This c 
y similar examples of grade 
necessitated a reduction in . oe 
reduction will be observed along the line.» 
