109 
has built for itself an elevated ridge across the bottom-lands, 
fifteen feet above the low-water mark, through which it pur- 
sues its tortuous course, flowing thirteen miles (See Pl. II.) to 
reach the Illinois, which is only five miles from the point 
where the Spoon enters the bottom-lands. The rapidity with 
which the alluvium is deposited at times is illustrated by the 
fact that the floods of 1898 left on the banks of the Illinois at 
the mouth of Spoon River a layer of earth nine inches in 
thickness. Nevertheless, we find an unusually large area of the 
bottom-lands occupied by lagoons or bayous, locally known as 
lakes, by marshes, and by bodies of water of an ephemeral 
character. Some of these, as, for example, Thompson’s Lake 
(Pl. I.), retain at all times their connection with the river, 
and receive their water supply wholly or in large part from it. 
Others, as Quiver and Matanzas lakes, retain their connection 
with the river, but are fed to a greater or less degree by 
streams and springs. They respond to changes in the river 
level and are subject to invasion by the river at times of rising 
water. During falling or stationary water, except at times 
of overflow, these lakes are filled with the clear water de- 
rived from their drainage basins, which stands in sharp con- 
trast to the turbid waters of the river. Such spring-fed lakes 
are not uncommon in the bottom-lands along the eastern side of 
the river from Pekin to its mouth. They derive their water 
supply from the sand deposits of the second bottoms, at whose 
margin they usually lie. Other tracts of the bottoms, lying at 
about the level of low water or losing their connection with 
the river before low-water mark is reached, become permanent 
marshes, as in the case of Flag Lake (Pl. Il.). In some in- 
stances where the body of water left by the overflow lies some 
distance above low-water level the characteristics of a marsh 
are not established, owing to the seepage and evaporation of 
the water and to consequent drying and hardening of the bed, 
and we have simply an ephemeral lagoon, as in the case of 
Phelps Lake. 
