PARTLY DISSECTED PLAINS IN JO DAVIESS COUNTY — 735 
thickness of the formation on which it is developed is likely to vary 
to a degree corresponding with the relief of the surface; (d) it is not 
likely to be parallel to underlying strata, but to rise or fall strati- 
graphically; (e) it would be expected to slope in the general direc- 
tion, corresponding to the direction of flow of the streams that made 
it, unless tilting took place after its formation; (/) much of the 
plain might be covered with river detritus such as fine gravel, sand, 
and silt, similar to the materials of river-made plains today. If 
such a plain is not parallel to underlying strata, but lies across their 
beveled edges, particularly if the strata are known to have con- 
stant thicknesses where undisturbed, it is almost certainly a result 
of erosion going to a late stage—a peneplain. This might not hold 
if the strata were the result of near-shore deposition, and thinned 
out shoreward. 
If the characteristics of the Niagara plain be compared with 
this set of features expected on a raised and partly dissected pene- 
plain, they are found to correspond only in part. Concerning the 
plain as it is in these quadrangles, (a) no distinct hills stand above 
it; (b) the flat has little relief—probably no more than could have 
been given it by erosion following the uplift; (c) the thickness of 
the formation under it varies slightly but not greatly in short 
distances; (d) its surface does not rise or fall appreciably in the strati- 
graphic section, even when considerable distances are considered; 
(e) it does slope in a general direction and at about the angle 
expected for a peneplain; (/) no sand or gravel or stream alluvium 
were discovered on the flat, and it is certain that no great amount 
of such material was there and has been subsequently removed, 
for it is not found on the bordering slopes, and some of the plain 
has been unaltered by any agent which could remove the alluvium. 
From the foregoing, it is seen that this plain is not clearly a raised 
peneplain; neither is it surely not a peneplain. If traced beyond 
the limits of this region, and found there to go from Niagara to 
Maquoketa to the north and from Niagara to something younger 
to the south, it will have been proven, nevertheless, to be a pene- 
plain. 
2. Ina second cycle of erosion, a flat of considerable magnitude 
might be formed on the top of a hard layer of rock, by the removal 
