BIG SPRING PRAIRIE. 69 



without forming a distinct or characteristic sand dune 

 as commonly understood. It may have been more 

 distinct in the past than at present. Now it may more 

 properly be termed a sand slope. 



The characteristic vegetation is quite similar to 

 that found on the north slopes of the ridges, the oaks 

 and hickories predominating. The grass is chiefly Poa 

 compressa. A portion of this sandy slope is under 

 cultivation. 



In Big Spring Township, Seneca county, there 

 occur three distinct dunes, two of them marked 5. D. 

 on map I, meaning simple dunes. The one to the 

 southwest, illustrated by fig. 14, will be referred to as 

 West Dune, the other as North Dune. M. D. C. in- 

 dicates a Miniture Dune Complex. 



By inspection of map I, it will be noted that 

 these dunes are located between the Bower Ditch on 

 the north and the outlet of the Big Spring on the 

 south. As a natural stream, the Bower Ditch had eroded 

 a perceptible valley on the ridge to the northeast, and 

 had doubtless carried a considerable amount of silt into 

 the old lake. The natural currents from the Big Spring 

 and those from the south also carry some silt along. 

 As these two silt laden currents encountered the sweep 

 of the prevailing westerly winds, much of this silt 

 was deposited, and in time, formed a sand bar or bank. 

 After portions of this sand bar became sufficiently ele- 

 vated to remain above the water throughout the year, 

 low dunes would be formed by the action of the winds. 

 Seeds would soon find lodgment, and plant life appear. 

 The same currents which transported the silt, would 

 also transport many seeds. The general order of the 

 advance of plant life on these dunes would resemble 

 that of the sand dunes along Lake Michigan. First, 

 there would appear annuals, then grasses and sedges, 

 which would act as binders of sand and inconsequence 

 low dunes would form; after this, shrubs and tree 



