THE INTERSTATIC PAlIK', TAYLOKS FALLS, MINNESOTA 33 



Gurleyville, Connecticut, de.scriV)e(l by Professor 1). F. Koons,* seems to 

 have been caused b}' varyinir conditions of erosion, there referable to a 

 nioulin torrent, rather tlian by inequality of hardness of the rock. 



In a few instances the rock wall of a pothole intersects one, two, or 

 three smaller potholes, which were partly worn away and merged with 

 the larger one. A good exanii)le of such a compound rock kettle is sit- 

 uated 5 to 10 feet south of the very deep kettle sounded by Dr Murdock, 

 the central hole there being five feet in diameter, with truncated holes 

 1 to 1-] feet in diameter. 



AVith the large giants' kettles, interspersed u})on the same area, are a 

 greater number of others that measure a few feet, or only 1 or 2 feet, or 

 even less than 1 foot, in diameter. These small kettles are mostly cylin- 

 dric, with de})ths ranging commonly from twice to five times their diam- 

 eter; but many are partially filled with sand, gravel, and rounded 

 stones. Rarely a pothole dis])lays a somewhat spirally grooved form, 

 sweeping around once, or nearly so, in the whole descent, due appar- 

 ently to erosion by the falling stream and stones after the hole had at- 

 tained almost its full de})th. 



Farther north several small tracts, varying from 20 to 50 or 75 feet in 

 extent, at heights of 50 to 70 feet above the river, including the highest 

 part of the rock surface between Trap Rock street and the river, have 

 many small potholes, varying from 3 or 4 feet to less than 1 foot in 

 diameter, occurring mostly in groups of five to ten near together, but 

 occasionally isolated. About forty were counted by me, and doubtless 

 others were overlooked. On larger tracts of the adjoining rock, includ- 

 ing its northeastern slopes toward the river, potholes are rare or entirely 

 absent. 



The most northern group is on a rock outcrop about 6 rods south of 

 the northern boundary of the park. Within a space of 15 by 20 feet on 

 this ledge are ten small potholes, from 4 to 10 inches in diameter, some 

 of them cylindric, but others shallow, like a bowl. Their edges, as is 

 usual elsewhere, are mostly cut abruptly into the rock, with sharp transi- 

 tion, at right angles, from the general rock surface. 



The other potholes of this vicinity may be more briefly described. 

 They are very scantily represented east of the river. One on that side, 

 having a diameter of 3 by 4 feet at its mouth, with increase to 4 by 52- 

 feet at the depth of 5 feet, below which it is filled with earth, is situated 

 about 20 feet northeast from the top of the head of the " Sentinel " or 

 " Old Man of the Dalles." It is only 8 feet back from the verge of the 

 cliff', which falls about 65 feet to the river. 



* Amer. Jour. Sci., third series, vol. 25, p. 471, June, I88;i. 

 VI— Hum-. Geoi,. Soc. Am., Vol. 12. 1900 



