ARTICLE XIV. 



Observations on the Geology of the Western Peninsula of Upper Canada, and 

 the Western Part of Ohio. By William B. Rogers, Prof of Natural Philoso- 

 phy in the University of Virginia and Henry D. Rogers, Prof of Geology in 

 the University of Pennsylvania. Read December 3, 1841. 



To determine the exact position of the wide-spread formations of the Ohio 

 River and the western Lakes in the general system of the Appalachian rocks, 

 as developed in New York, Pennsylvania, Virginia and Tennessee, is a problem 

 of much interest in the geology of the United States. It is indeed an essential 

 preliminary to some of the most important inquiries of a scientific kind which 

 can engage American geologists. The gradations of type in these ancient se- 

 dementary deposits, which extend, we believe, more or less to their included or- 

 ganic remains, and which must be first studied before we can clearly understand 

 the physical changes that have marked the history of these strata, will not be 

 reduced to their true laws until the continuity of the eastern and western 

 rocks shall have been fully established. 



But this determination is attended with many difficulties, since the very 

 variations of type referred to, are often of a nature to mislead; their true value 

 not being recognised until the investigation is nearly over. Besides these lia- 

 bilities to error from changes of type imperfectly ascertained, there are others 

 incident to the region before us where the unsupplied links between the eastern 

 and western strata are to be sought. These are the horizontality of the rocks, 

 the deep covering of drift which generally conceals them and the interruption 

 of their range by the interposed waters of Lake Erie. 



