GENERAL TOPOGRAPHIC FEATURES 217 



discharge waters from the inner lowland into the Ontario lowland, and 

 thus traverse the limestone belt, and those whose catchment basins are 

 located wholly on the limestone uplands. 



In general it is found that the upper parts of the valleys of the first 

 type are very steep-sided and flat-bottomed where they traverse the 

 cuesta. In many cases both sides are inaccessible, though not necessarily 

 vertical, cliffs as much as 125 feet in height, with a flat-bottomed valley 

 between. The width of the valley varies somewhat, but rarely exceeds 

 a mile and a half or is less than half a mile. In most cases the upper 

 parts of these valleys, near where they pass through the cuesta front, 

 form the basins of long, narrow lakes. Such lakes as those on the Cata- 

 raqui creek above Kingston mills, Collins lake, Loughborough lake, 

 Sydenham lake, and several others in Ontario are of this type. The 

 water seems in some cases to be held back by a drift dam, which partly 

 blocks the lower part of the valley. Certainly in some cases, in all prob- 

 ability in most cases, the present lake basin is a rock basin and the ex- 

 istence of the present lake is due either to warping or possibly to differ- 

 ential erosion by ice. 



These valleys in their lower reaches toward the lake become broader. 

 In New York the sides usually have about equal slopes, the general trend 

 of the valley being in the same direction as the dip of the rocks. North 

 of lake Ontario, however, where the trend is not always accordant with 

 the dip, in many instances the southeast side of the lower portion of a 

 valley is much steeper than the northwest side. Many of the valleys are 

 bounded by a well marked rock escapement, which may be traced from 

 the cuesta front along the valley side almost to lake Ontario. In their 

 lower reaches the breadth of this first type of valley may be as much as 

 5 miles. The intervalley uplands in ground plan will thus have the 

 form of a scalene triangle, with the base at the cuesta front and the apex 

 of the triangle pointing toward lake Ontario. The inland portions nearest 

 the cuesta are broad and flat, with very little or no soil cover. As the 

 valley widens the gradual encroachment of adjacent sides of neighboring 

 valleys narrows the flat intervalley area. In places, however, it so well 

 retains its character that it ends in a wedge point which can be located in 

 the field without difficulty, where the encroaching gradient curves of ad- 

 jacent valley sides have met. In a few places close to the discharge point 

 of the present valleys on the bay of Quinte the present surface of the 

 intervalley ridge will thus lie below the plane of the upland surface. 

 The majority of these valleys can be traced by aid of the soundings for 

 some distance out from the shoreline and under the waters of the present 

 lake Ontario. 



The valleys of the second type, which head on the upland, are, in their 



