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 undercultivation, 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 Quercus 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 I. 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 Ecolog1- 
cal Relations of the Vegetation on the Sand Dunes of 
Lake Michigan.’”’ Only here the zones would te 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 
