Eskers of the Kansau Epoch. — Hershet/. 237 
the Ptiget sound border, tends to ney,-ative the theory which 
assigns that series to a relation transitional between the Mes- 
ozoic and Cenozoic formations. On structural grounds at 
least, its upper limit seems to be no higher than the Chico or 
superior portion of the Upper Cretaceous of the southern Pa- 
cific border, in common with that of the Carbonaceous series 
of eastern Vancouver and the strait of Georgia. 
(To be continued.) 
ESKERS INDICATING STAGES OF GLACIAL RE- 
CESSION IN THE KANSAN EPOCH IN 
NORTHERN ILLINOIS. 
By Oscar H. Hershey, Freeport, 111. 
(Coniinued from page 201K) 
Now, while the evidence clearly proves that the esker ma- 
terial was not gathered from tXte till of the vicinity, it may be 
claimed that it was derived from englacial local drift which 
was carried up into the body of the ice at some distance east of 
this district, and which, by the ablation of the peripheral por- 
tion of the ice-sheet, became superglacial and was swept into 
the streams flowing over the ice. This hypothesis, however, 
is effectually disposed of by a study of the englacial drift of 
the district. On the south side of the Pecatonica valley, east 
of Ridott, certain high flat- topped ridges have had their re- 
siduary clay and chert abraded from them, but the ice failed 
to deposit its ground moraine over them. Upon tlie final 
abandonment of the region, all the englacial material which 
the ice contained over any given spot must have settled down 
upon these ridges of bare rock. The finer portion of this en- 
glacial material was largely removed by subsequent subaerial 
erosion, but all the pebbles and boulders over one inch in di- 
ameter must still remain on these ridges. Some of these areas 
of nearly bare rock cover several square miles, and we find 
scattered over them a small amount of well rounded foreign 
material and a few erratics of boulder size. Over the gravel 
beds and over the till or ground moraine of the entire district 
these scattered boulders are found in about the same propor- 
tion as over the ridges of nearly bare rock, besides a small 
amount of pebbles of lesser size. We are thus able to deter- 
mine, with a tolerable degree of certainty, the following facts 
