IROQUOIS PLANE IN REGION OF COVEY HILL 225 



the level of the Iroquois Beach farther west. The floor of this outer 

 valley represents a baselevel of considerable duration, perhaps equal to 

 that of the Iroquois Beach, with which it may be correlated until more 

 complete surveys have been made. It is the strongest evidence of a long- 

 continued water level near this elevation. It is about 100 feet below the 

 depression across Covey Hill, which has been regarded as the spillway 

 of a glacial lake, or approximately the difference between the higher ter- 

 races and the Iroquois level, occurring in the Mohawk Valley and also 

 north of the Adirondacks. If this be the correct interpretation, as I be- 

 lieve, it is confirmatory of my suspicion, as expressed in my last year's 

 paper, 8 that the spillway across Covey Hill belongs to a water level an- 

 terior to that of Lake Iroquois. 



The extension of the Iroquois plane to the northeastern angle of the 

 Adirondacks highlands indicates that the isobars have the direction of 

 north 67° east, or that the rise of the land is in a direction of north 23° 

 west. It has already been shown (from triangle 12) that the deforma- 

 tion crossing this isobar westward of Parishville reaches 6 feet per mile. 



There is no reason to suppose that the rate of deformation at right 

 angles to this isobar differs greatly in the vicinity of Covey Hill from 

 that which obtains farther west. However, the rate of tilting to the 

 southward naturally diminishes, as in the region of the Mohawk Valley ; 

 and indeed, in proceeding southward along Lake Champlain, Professor 

 Woodworth found such to be the case, as shown in his excellent memoir. 9 



Deformation observed in the marine Beds at Montreal 



Above the marine terraces at Montreal other beds containing Saxicava 

 rugosa, Macoma groenJandica, etcetera, occur at elevations of 536 and 560 

 feet above sealevel. Again, in the angle of the river east of Mooers 

 Forks, marine deposits were found by Doctor Woodworth at 340 feet 

 above sealevel. The deposits of both localities are familiar to me. Their 

 distance apart is 38 miles in a direct line nearly north and south. While 

 the marine beds may have been somewhat higher in one or both localities, 

 such have so far not been found, so that we may measure the approxi- 

 mate deformation by their differences of elevation, which is between 5 

 and 6 feet per mile. This agrees with the tilting of 5 to 6 feet per mile 

 seen farther west. 



The warping of the lower 525-foot beach at Covey Hill is reported (by 

 Fairchild 10 ) to be 3 feet per mile south 20° cast. This is on a shoreline 

 more recent than the Iroquois, where the deformation is less. Projecting 



"Bull. Cool. Soc. America, vol. 23, 1912, pp. 471 lie. 



9 New York Stale Museum Bulletin No. 84, Hinrl P, opp. p. 226. 



'" lb., Run. 158. 1012. p. 88. 



