.1. VV. SPENCER — THE IROQUOIS SHORE. 189 



Beyond Natural Bridge there are extended gravel plains, in height conforming to 

 the terraces at the old mouth of Indian river; but these are often more or less 



pitted. 



These plains appear to me as due to the presence of floebergs or other masses of 

 ice stranded upon the old shore. Even if they were shore deposits formed in glacial 



lakelets, their elevation is such as to show a common water level. They now face 

 a lower descending country to the northwestward, and are deformed by the gradual 

 warping toward the northeast. At I'iteairn, the valley is 200 feetor more in depth, 

 Conning a deep channel in the late expansion of the Laurentian archipelago. High 

 on the sides of the valley /.ones of howiders, which are so often characteristic of 

 old shore lines, are found at heights in keeping with the deformed Iroquois beach. 

 A little north of East Pitcairn, there is a fine display of terraces, with heach 

 structure. These are partly in front of a now unimportant valley. There are 

 several ridgelets, the highest being 942 feet; hut the most important is 930 feet 

 above tide. These ridgelets descend to a terrace or frontal plain 60 feet below. A 

 short distance beyond, the terraces of Oswegatchee river are seen. .Inst north of 

 Fine, they close around and connect a rocky island with the eastern side, and form 

 a soil of harrier beach. This bar lias an elevation of 972 feet. All of the above- 

 recorded terraces were leveled. The following are of barometric measurement. 

 The rise in height in these beaches corresponds to the deformation of the Iroquois 

 heach, increasing from live to six feet or more for miles toward the northeast, 

 which amount ought perhaps to be slightly modified, owing to imperfect identifi- 

 cation in the crests of these terraces or the absence of some portions of the highest 



ridgelets. 



The next ureal valley is that ofGrassy river. At Clifton Forge {Clarksboro), the 

 .ild mouth of the valley is well defined byabeautiful gravel terrace at 1,055 feet 

 (hard, with an inferior terrace or ridge at 45 feet below. Lower than this no well 

 marked -ravel terrace occurs; hut at S50 feet there is an extensive sand plain, 

 forminga terrace confined to the valley. The terrace in the last valley is nearly 

 due north of that at fine, and appears to represent a warping of eight feet per mile. 

 Out probably the barometric measurement is responsible for the apparent increase 

 in rate of elevation. Still, the northern uplift may probably exceed that to the 

 northeast. 



The chain of observation was continued by Mr. Gilbert and myself to Racket 

 river. The elevations were not satisfactorily obtained, as the changing weather 

 greatly affected the barometer, especially above South Colton. At South Colton j 

 there is a sandy plain at about '.Mo tbet (bar.), apparently corresponding to the 

 plain.- below Clifton Forge and Fine. Racket river presents an interesting change 

 of channel near St ark post office. It.- old course was in a broad valley, now occupied 

 by ( 'old water creek as far as South Colton ; but after the Pleistocene revolution, it 

 cut across hard rocks and deserted its old channel. Following up the Coldwater 

 valley, we reached a broad sandy terrace underlain by gravel. This plain forms 

 terraces extending northward along the sides of the valley. It- elevation is 

 1,215 (? bar.; the weather was very threatening). Other deposits were noted at 

 1,350 feet, which' were probablj older river terraces. Again, on the brow of the 

 plateau facing Potsdam, there was a plain at 1,160 feel with a bow Ider pavemenl in 

 front of it. The value of these measurements is so impaired thai they are only 

 important in identifying continued elevations of the terrace plains near the late 

 outlet- of the valleys as far eastward as Rackel river. In descending from the la-t 



