EroHioii Cycles in Xoftlncestertt Illinois. — IJershey. S\) 
baselevels approach and at times merge into each other;* 
and (c) a large portion of the province has been glaciated so 
as to obscure the preglacial topography. Hut a few sugges- 
tions, as to what correlations are probable and apparently 
supported by present data, will not be out of place. 
During the past summer, Dr. H. B. Kiimmel, after a short 
study of the geomorphology of a portion of the Drif tless Area 
in Lafayette and Grant counties, Wisconsin (immediatel}'" 
adjoining our district on the north), published his conclusions 
about as follows :f He recognizes a peneplain consisting of a 
"broad undulating upland, with an elevation of from 850 to 
1.000 feet;" a few " monadnoeks rising above it" and cul- 
minating in the Platte mounds, 1,250 to 1,300 feet above 
the sea: and a system of comparatively deep narrow valleys, 
trenched below the peneplain. These valle3^s, because of their 
being bounded by steep bluffs, surmounted by gentle slopes, 
he considers as the product of two cycles of erosion. " The 
process by which the valleys are being formed is not a direct 
continuation of the process by which the gentle upland slopes 
were fashioned. The valleys were cut in the upland surface 
after it was elevated from the low position which it had dur- 
ing its formation." In these adjoining districts belonging to 
the same area of "• uplift," the correlation of the several base- 
level planes is easy and definite. Dr. Kiimmel's peneplain is a 
continuation (without further uplift) of peneplain No. 2 in 
the more southern district. The Platte mounds belong to the 
same series as the monadnocks in Illinois. The gentle upper 
slopes of thevallej'S are equivalent to peneplain No. 3 in the 
Pecatonica basin; and the narrow bluff-bound caiions are an 
undoubted continuation of the similar valleys in Illinois. 
The Cretaceous peneplain has been recognized in southern 
Arkansas by Mr, L. S, Griswold.;J; It emerges from under the 
Cretaceous formations as a gradually rising plain, •* At a 
*Thi8 idea was first suggested to the writer V)y Mr. M. R. Campbell, 
who, in conjunction with C. W. Hayes, after a complete study of the 
geomorjjhology of the southern Appalachians, has traced the Cretace- 
ous peneplain in Tennessee and Kentucky, near the Ohio river, to a 
position only 200 feet above the Tertiary peneplain. They think it pro- 
bable that the Cretaceous peneplain merges into the Tertiary over a 
portion of the upper Mississippi and Ohio basins. 
tScience, June 28. 1895, pp. 714710. 
^Proceedings of the Boston Society of Natural History, vol. xxvi, 
author's edition. May 14, 1895. 
