214 A. W. G. WILSON — TRENT RIVER SYSTEM 



those regions. In New York state, south of Stony creek (about 6 miles 

 south of Sacketts harbor), the bedrock topography becomes obscured 

 by morainic deposits. But even here, particularly in the vicinity of the 

 lake shore, certain of the features whose presence would be expected 

 from their occurrence farther north are found to be present, partly ob- 

 scured by drift it is true. 



In Ontario the area whose bed-rock topographic features can be accu- 

 rately determined includes the whole of Prince Edward county. Here, 

 although there is abundance of drift as a thin veneer, the farmer in 

 plowing is often turning over more or less decayed rock, unquestionably 

 in situ, which the writer regards as probably of pre-Glacial origin, a 

 question to which reference will be made below. The heavy morainic 

 deposits of central Ontario lie close to the lake from near Toronto to the 

 vicinity of Trenton. At Trenton their southern edge turns inland, and 

 they extend eastward to near the village of Croydon. Northward they 

 reach almost to the edge of the Black River limestones at the borders of 

 the Archean; but they are not continuous, numerous exposures of bed 

 rock being known north and east of Trenton. South and east of the 

 line between Croydon and Trenton the character of the bed-rock topog- 

 raphy can be determined without difficulty. All along the line of con- 

 tact between the Black River limestones and the Archean, within the 

 limits of the area under discussion, from the south of Carthage, in New 

 York state, to west of lake Simcoe, in Ontario, the topographic features 

 of the limestones are practically unobscured by drift. Outcrops with- 

 out cover of any kind are very frequent, particularly in the province of 

 Ontario, where there seems to be much less drift cover than over the 

 similar region in New York. 



Glacial or post-Glacial movements have produced one very important 

 change. The present attitude of the region is not that which it had at 

 the time the topographic features it now possesses were produced. There 

 has been local differential movement which has modified the original 

 relative attitudes of the different parts of the region. Probably there 

 was at the same time a considerable amount of regional movement by 

 which the general attitude (with respect to sealevel) of the whole area 

 was altered to its present position, accompanied by certain modifications 

 of the drainage lines. Recent process has effected only minor and local 

 changes, such as the partial erosion of portions of the drift deposits or 

 the local modification of the topography where differential movements 

 or other causes had produced lake basins. One of the most noticeable 

 of these recent changes is the blocking of the lower reaches of a number 

 of partly submerged valleys by the formation of bars across their ends, 



