
























154 THE LAKES OF IOWA,— PAST AND PRESENT. 
color from top to bottom, and a hundred miles of distance 
show no more difference than a hundred feet. It is ofa 
slightly yellowish ash-color, except where rendered darker 
by decaying vegetation, very fine, not sandy, and yet | 
adhesive. At the surface it makes excellent soil, and is just 
as fertile if obtained at a depth of two hundred feet. Itis _ 
easily excavated by the spade alone, and yet it remains st 
unchangeable by the atmosphere and frost, that wells dug in 
it require to be walled only to a point just above the water- 
line, while the remainder stands so securely without suppot 
that the spade-marks remain upon it for many years. - d 
embankments upon the sides of excavations stand likes 
wall, showing the names of ambitious carvers long after at 
ordinary bank of earth would have disappeared. As thii 
part of the valley of the Missouri River below the lake 
deepened during the Terrace epoch by the natural process 
of erosion, the peculiar material which its own waters hal | | 
previously deposited offered little obstruction to that po 
cess, but was readily swept out again as muddy water, af 
sent on its way to the sea. Thus no more of it was 
than served to form the valley, which is from four to t 
miles wide, while the larger part remained, forming * 
bluffs, and extending far inland from the river. The #0" 
tary streams which at first emptied into the lake, now tr 
its ancient bed of sediment to the river, and have eut 
their own valleys to meet it. The sides of these 7 
_ where they traverse that sedimentary deposit are steep 
the river-bluffs, and the streams being smaller, their 
arè narrow and very deep. This is particularly | 
all those Iowa streams that empty into the Missouri 
above Council Bluffs, and they thus present great OF a 
the construction of lines of railway directly east and 
through that State. For this reason, and for the pur 
connecting with the great Pacific Railway at ye 
more northern of those lines are diverging to the SOM g 
down the valleys of the streams, instead of crossing them» 

