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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 PI. 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 

 (PI. II.), 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 (PI. II.). 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. 



