Glacial Deposits in Driftle.is Area. — Sardeson . 399 
thus showing that glaciers did not necessarily remove it. I 
have found residuary clay on the Niagara limestone in places 
in lovv^a where glaciation had twice obtained. At Free- 
port the northern drift is mixed in the upper part of the re- 
siduary clay, but otherwise the latter is not peculiar. It seems 
to lue evident that the existence of residuary clay in the 
"driftless area" is not proof that no glaciers existed there, 
during the lowan and Kansau (or pre-Kansan ) drift periods. 
If at Freeport the glacier had carried only residuary clay and 
chert, without northern drift, we should probably scarcely 
find traces of its former existence. Local glaciers in the "drift- 
less area" would evidently descend along the natural valleys 
merely, transporting materials in the direction of the surface 
drainage, and probably but little materials at that. Under a 
loess mantle slight evidence of drift is easily concealed more- 
over. Along the railway from Freeport to Dodgeville is one 
favorable line for investigation, because of the cuttings, 
and there I have been able to devote a few days only to this 
and other geological investigations. 
About four miles below Dodgeville, Wisconsin, the Illinois 
Central railway cuts through a mass of unstratified residuary 
clay with chert besides some loose blocks of Saint Peter sand- 
stone. The clay here, as not rarely elsewhere, contains round- 
ed grains of quartz, probably from the sandstone. The ex- 
posure is ten or more feet deep and about 100 long, and no 
evidence of water action was found in any part of it. but on- 
ly the characters of boulder cla3^ The mass appears superfi- 
cially to be 20-30 feet thick, 300 yards long across the valley 
and 200 yards wide. The creek or river has cut across its 
west end, else the mass obstructs the valley. Its position re- 
vealed to rae no explanation of any origin except that of an 
end moraine. It lies in the horizon of the Saint Peter sand- 
stone, above the flood plain of the river and had it not been 
for fortuitous exposures it might have been passed over as 
one of the loess-covered Shakopee and ()ner>ta dolomite swells 
that are so common in the East Peccatonica valle3^ 
Half a mile farther down the valley, the railway cuts 
through a loess-covered Oneota dolomite swell high above the 
flood plain of the river. The dolomite formation is covered 
by residuary clay, and on the lower or southern side by an 
