ANCIENT GLACIERS. Ill 



" 2. Peat or Soil under Loess. — This does not signify 

 much if the loess was formed in a lake subject to oro- 

 graphic oscillations, or if, as I am coming to believe, 

 it is a fluviatile deposit of an oscillating river like the 

 Hoang-Ho on the great Chinese plain. It at least does 

 not mean an interglacial epoch. 



" 3. Wood and Dirt rearranged, not in situ. — This 

 occurs either in subaqueous or in subglacial deposits. I 

 have found drift-wood in the lower layers of the loess 

 here, but not in situ. I have frequently found traces of 

 wood in till in Dakota, but always in an isolated way. I 

 think, from reading statements about the deposits in east- 

 ern Iowa, that most if not all of the cases are of this 

 sort. Two things have conspired to lead to this error: 

 one, the influence of Cr oil's speculation ; and the other, 

 the easy inference of many well-diggers, and especially 

 well-borers, that what they pass through are always in 

 layers. In this way a log becomes a forest-bed. Scat- 

 tered logs and muck fragments occurring frequently in a 

 region, though at different levels, are readily imagined by 

 an amateur geologist to be one continuous stratum ante- 

 dating the glacier or floods (as the case may be in that 

 particular region), when, in fact, it has been washed down 

 from the margin of the transporting agent and is con- 

 temporaneous with it. I suspect the prevalence of wood 

 in eastern Iowa may be traced to a depression of the 

 driftless region during the advance of the glacier, so as to 

 bring the western side of that area more into the grasp 

 of glacial agencies. 



" 4. Peat between Subglacial Tills. — If cases of this sort 

 are found, they are in Illinois, Indiana, and Ohio. Pro- 

 fessor Worthen insisted that there were no interglacial 

 soils or forest-beds in Illinois ; and in the cases mentioned 

 in the State reports he repeatedly explains the sections 

 given by his assistants, so as to harmonize them with that 

 statement. I think he usually makes his explanations 



