ca) 
Tue Witson BuLretin, No. 74. 
the region is not typical of central Illinois in general, for, as 
it is well known, the greater part of central Illinois is occu- 
pied by crops of one sort or another, but principally corn in 
black prairie soil. 
This city, on the other hand, lies in about the center of the 
broad valley of a post-glacial stream, which was some fifteen 
to eighteen miles wide in this vicinity. The soil is either 
nearly pure sand or a sandy loam, yellowish in color, very dif- 
ferent from the character of the average soil of Central Illi- 
nois. There are extensiv bottom lands in the immediate vi- 
cinity of the Illinois River of the present day which flows 
thru the center of this sandy area. In these situations there 
is usually a coating of muck laid down over the sandy bot- 
tom of the original stream. 
The present river in this vicinity is about 4 miles wide, but 
taken together with the overflowed area it is from 0.5 to 3.5 
miles from shore to shore. The bluffs which mark the original 
valley in post-glacial times are, of course, often farther apart. 
The water and the bottomlands furnish a typical avian envi- 
ronment, which is populated by its usual associations of birds. 
The east shore of the river is a modified dune surmounted by 
oak woods. The sandy uplands stretching back from this 
dune are quite largely under cultivation, but scattered here 
and there are areas of bunchgrass, blowouts, black oak and 
blackjack oak woods. Drainage is almost entirely subterra- 
nean and consequently creeks and swamps are a very minor 
part of the sum total of avian environments. 
‘For a fuller and more extended discussion of the general charac- 
ter of this region, together with its history, consult the following: 
Torbes, S. A. The Biological Station in the Biennial Report of 
1895. the Director 1893-1894. Illinois State Laboratory of 
Natural History, pp. 1426, with excellent illustra- 
tions. 
Forbes, S. A. Biennial Report of the State Laboratory and Special 
1897. Report of the University Biological Wxperiment 
Station 1895-1896, with map and illustrations. 
Kofoid, C. A. The Plankton of the Illinois River 1894-1899, with 
1903. introductory notes upon the hydrography of the Illi- 
