﻿GEOLOGY OF THOUSAND ISLANDS REGION 89 



tion. One of the best examples of such a gorge is that of the 

 Perch river at Limerick. Many brooks disappear entirely under 

 the Watertown formation, forming long underground courses and 

 caves. Several such courses are know in Watertown, where, how- 

 ever, they have been filled by the damming up of the river. Others 

 are known below Watertown and at Black River village. 



Phenomena entirely peculiar to this formation in the region are 

 the inliers at the Natural bridge and Limerick. A glance at the 

 Watertown-Leray belt on the Clayton sheet north and east of Chau- 

 mont Ibay reveals the fact that in several places the typical Lowville 

 beds appear from beneath the Watertown-Leray limestones. These 

 inliers consist of elongate strips of Lowville limestone exposed 

 along brooks and surrounded on all sides by the Watertown-Leray 

 limestones. The conditions which have produced this peculiar and 

 rare form of inlier are the following: The coincidence of the dip 

 of the beds and of the course of the brook and the greater resist- 

 ance of the underlying Lowville limestone to solution. The brook 

 as a rule reaches the inlier by a fall, and finally leaves it again by 

 very gradually passing again upon the overlying rock. 



A very characteristic example of such an inlier is seen along 

 Threemile creek and a very large one at the head of Guffin bay. 

 The most interesting of all is that below the village of Limerick on 

 Perch river. It begins with the fall shown on plate 23 and ends 

 above the Natural bridge. At the latter place the river passes under- 

 ground through a ridge of Watertown-Leray rocks crossing the 

 valley. Below the bridge the river reappears for a short distance 

 [pl- 38] and disappears again, its course being thence traceable as 

 a depression between the cliffs of Watertown-Leray rocks on 

 both sides. The depression shows in the different tilting of the 

 huge blocks of the Seven foot tier that it is the result of a gradual 

 sinking down O'f the whole mass ; and this indicates that the river, 

 which has its underground course on the top of the typical Lowville 

 beds, is dissolving the Watertown-Leray beds along its course from 

 the base upward. There is little doubt that also the inlier above the 

 Natural bridge, which can not have been produced by normal cor- 

 rasion, is the result of solution of the Watertown-Leray beds, and 

 that finally also between the Natural bridge and the lake the typical 

 Lowville beds will be exposed and the river flow again overground, 

 as it already does just below the bridge. 



One of the best exposures of the Watertown-Leray beds is that 

 at Klock's quarry, at the end of Huntington street at Watertown. 

 This section which is here inserted, begins close to the base of the 



