Trans. N. Y. Ac. Scz. 182 June 5, 
wide, risiag in Westchester County, and discharging its waters into 
Long Island Sound, nearly opposite College Point. 
It occupies, however, the bottom of a valley, which, at Williamsbridge, 
must be at least half a mile wide, probably more, and two hundred 
feet deep below the summits of the hills which bound it to the east and 
west. This great depression extends northwardly with the river, but 
I have not studied it any further north than White Plains, where it is 
quite broad. At a point about three-fourths of a mile below the 
Williamsbridge station of the Harlem Railroad, this valley is some- 
what narrowed, and much interrupted by a ridge of rock running 
parallel with the present course of the stream, viz., very nearly north 
and south. The Bronx flows through a narrow gorge cut out of this 
rock. It is near the northern end of this ridge where the pot-holes 
under consideration are situated. Leaving the train at Williamsbridge, 
and ascending the stream, we pass through a stretch of swampy 
ground of considerable botanical interest, it being the only known 
habitat about New York for Avrzsema Dracontium, the “ green 
dragon,” we pass the old bridge before mentioned, and enter the grove 
of hemlock. The first pot-hole to be observed is quite imperfect, only 
a portion of the western side now remaining, the rest having been 
broken away. It bears S. 50° W. from the western end of the bridge, 
at a distance of 76 feet. The bottom of the pot is about 18 feet 
‘above the present level of the Bronx at this point, but this is less than the 
natural height would be, as the water is backed up by a dam half a mile 
below. Measurements indicate that the total depth of the hole must 
have been about nine feet, and at half its height the diameter not less 
than ten feet. This must, however, have very rapidly decreased 
towards the bottom. 
Proceeding 136 feet south from the bridge, and then up the rocks to 
a point 63 feet from the river bank, the second pot will be found. This 
is much more perfect, and is quite a noticeable object. The bottom of 
this one is twenty or twenty-two feet above the present water level. 
The hole is oval in section, about four-fifths of the original outline still 
remaining, only the outer (the eastern) end being broken away. Its 
dimensions are as follows: 
Total indicated depth, Io feet. 
Depth of nearly perfect lower part, 4’ 6". 
Depth of entire basin at the bottom, Io". 
Shortest diameter, 5’. 
Original longer diameter probably about 6’. 
Distance from back to broken face, 4' 7”. 
The lower part of this pot is very well preserved ; the bottom and 
sides are very highly smoothed, indeed quite polished. The upper por- 
