516 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



probably less, though it is not certain how much filling occurred beneath 

 the margin of the ice while it was forming the moraine. 



This moraine presents, on the whole, a more variable stracture than 

 that of the Mississinawa moraine. Not only are gravel knolls more fre- 

 quent among the till swells but there is a large amount of gravel and sand 

 interbedded with the till sheets. A large part of the moraine, however, 

 consists of ordinary till, such as constitutes almost the whole of the Missis- 

 sinawa moraine. 



Bowlders are fully as conspicuous as on the Mississinawa moraine, 

 there being a sufficiently large number at the surface to supply nearly 

 every farmer with material from his own farm for foundation walls for 

 buildings and for other purposes. Along the Wabash River, near Hunting- 

 ton, and also in portions of the belt in Whitley County, they are so numerous 

 as to be a great hindi-ance to the cultivation of the soil. They consist 

 almost entirely of crystalline rocks (mainly granite) of Canadian derivation, 

 but occasional Paleozoi'c limestones occur which are of less remote derivation. 

 The bowlders are subangular to well rounded and but few of them show 

 striation. The few that are striated testify, by the fresh appearance of the 

 markings, that the general absence of striation can not be due to weather- 

 ing. It is more probably due to transportation on the surface of the ice 

 sheet, where glacial abrasion was ineffective. A large proportion of the 

 pebbles in the till and gravel are limestone, derived from but a short 

 distance to the northeast and thus are in striking contrast to tke surface 

 bowlders. 



C. S. Artlmr, of Portland, Ind., has collected many fossils from 

 stones embedded in the drift of Jay Coimty. They include Devonian, 

 Upper Silurian, and Lower Silurian species. Among the Lower Silurian 

 fossils the \sim.el\ihra,nGh. Ambonychia costata and the trilobite Calymene hlumen- 

 bachia are said to have been identified. In discussing the occurrence of 

 these fossils McCaslin suggests \that the ice sheet probably reached the 

 Hiidson River formation at a place north or east of the points where the 

 fossils occur, and that, since the Upper Silurian limestone forms the surface 

 rock over that portion of Indiana and the adjacent portion of Ohio, this 

 formation must have been entirely removed by erosion in some undiscovered 

 locality. A boring made at Geneva, Ind., in 1888, has demonstrated that 



' Twelfth Ann. Kept. Geol. Survey Indiana, 1882, p. 164. 



