68 BIG SPRING PRAIRIE. 



5th. On areas where sod and surface soil have 

 been burned by prairie fires. 



LIMESTONE OR OUTCROP ISLAND. 



The highest portion of this area is about four or five 

 feet higher than the surrounding prairie. There is no 

 actual outcrop of Niagara limestone, but it is covered 

 with a rocky clay soil, similar to that of the ridges. 

 When this region came under the writer's observation, 

 it was under cultivation, but some of the original trees 

 were still standing. There were nine oaks in a 

 flourishing condition, and three dead ones still standing. 

 The oaks were chiefly Ouercus alba (white oaks ) There 

 is no doubt but that this was the first wooded area of 

 this prairie, the forest appearing but little later than 

 that on the neighboring ridges, as the island was former- 

 ly much higher without doubt, and has been consider- 

 ably worn down by erosion. 



SAND DUNES AND BEACHES. 



In Big Lick Township, Hancock county, there 

 occurs an old sand beach or low dune along the 

 slope of ridge as indicated on map 1. This beach or 

 dune was blown up by the north and northwest winds 

 while the prairie site was still a lake. First, a sandy 

 beach was formed, with its three zones of lower, middle 

 and upper beaches as discussed by Dr. H. C. Cowles of 

 the University of Chicago in his treatise " The Ecologi- 

 cal Relations of the Vegetation on the Sand Dunes of 

 Lake Michigan." Only here the zones would be nar- 

 rower, and different species would occupy the upper 

 and middle beaches of this area, from those found on 

 the corresponding zones along Lake Michigan. It 

 would be interesting to know what these first species 

 were, but there is now no means of determining this, 

 and it would be useless to speculate. On account of 

 the slope of the ridge, the sand was blown up the slope 



