140 THE JOURNAL OF GEOLOGY. 



determination. None of them exceed one-sixth of an inch in 

 diameter. Professor Chamberlin reports having observed a bed 

 containing moUuscan shells between the newer and older till- 

 sheets at-Greensburg, Indiana. (See Third Annual Report U. S. 

 Geol. Survey, p. 333). Positive evidence is wanting as to 

 whether these fossiliferous silts are of the same age as' the silts 

 which cover the district outside the moraine, but they appear to 

 have about the same horizon. No fossils have been found in the 

 silts outside the moraine. It seems not improbable, however, 

 that if originally present their exposed situation is such that 

 the fossils may have been dissolved and removed by leaching. 



In the case of streams leading southward from this region of 

 newer drift, careful discrimination is necessary to decide the age 

 of terraces. The coarse, gravelly terraces of the Little Miami 

 valley are referred to the stage when the outer moraine was 

 formed. This valley carried a larger volume of water at that 

 time than in later stages of glaciation, because it was more favor- 

 ably situated for receiving glacial waters. The Great Miami 

 valley was apparently flooded as much during later stages as at 

 this time, and its gravels are largely of the age of the later 

 moraines. The Little Miami gravels are made up, in large part, 

 of coarse material as far down as the mouth of the stream, peb- 

 bles two to four inches in diameter being common. The coarse- 

 ness of the material testifies to a fair gradient, presumably as 

 great as the present altitude of the country affords. The gravels 

 rise to a height of but fifty to one hundred feet above the pres- 

 ent stream, and are near the bottom of the valley trench, for the 

 uplands bordering this stream stand 300 feet or more above its 

 bed. The flood stages, though characterized by a much more 

 vigorous drainage than that which obtained while the silt was 

 being deposited on the bordering uplands, did not reach by 

 nearly 200 feet the limit reached by the silt-depositing waters 

 — a fact which seems to be capable of explanation only on the 

 assumption of great orographic movements. 



De glaciation interval in the later drift series. In his reconnais- 

 sance of Western Ohio, some ten years ago. Professor Chamber- 



