FIFTH REPORT OF THE DIRECTOR I908 l6l 



line that may reach many miles. These lake excavations caused 

 by wave and undertow are not only smaller and more shal- 

 low than stream potholes but are cut at the same level on a line 

 surrounding a large territory and any higher linear series 

 would be indicative not of the phenomena of former stream ac- 

 tion, rapids or falls, but of former wave action. A new term 

 for these shore line excavations would be conducive to clear think- 

 ing and on account of their difference in diameter, depth, position, 

 arrangement, locality and manner of formation, a new term is 

 certainly due them. The name cupholes is proposed and will be 

 used hereafter. 



That these cupholes are due in great measure to vortexes in the 

 undertow from wave action is shown by plate 5, which presents 

 a view of the seaward end of the glaciated rock boss in 

 part shown in plate 3. The cupholes are arranged in curving 

 lines which all run from the central ridge of the rock mound and 

 take the lines of the undertow. Many cupholes may be seen to 

 have become confluent and the figure makes a very interesting 

 study. The absence of pebbles is shown, as is also the presence 

 of minor cupholes within the major. 



Just under the edge of the water all the cupholes have become 

 confluent and the result is a distinct shelf, about a foot wide, cut 

 completely around a more exposed portion of this glaciated boss. 

 Just outside the edge of the shelf is a fine clay bottom from 

 which the action of the present low water has removed some few 

 centimeters and cut the surface into a very irregular pattern in- 

 dicative of varying density. Whether or not Lake Champlain is 

 repeating a former process and removing some of its own sedi- 

 ment or whether the low water is removing the sediment of the 

 Hochelagan sea, where it covers the till, is not at all certain; but 

 the distinct rock shelf cut by the cupholes would indicate that 

 Lake Champlain had never cut lower. 



These cupholes may be found around the entire island and ex- 

 tending deepest where the undertow is greatest. There is no 

 higher line shown on the island and the retreating Hochelagan 

 sea found no resting place until the waters were freshened by the 

 stream inflow and the lake reached the present comparatively 

 stable level. 



The figures given show in each case glaciated surfaces run- 

 ning from above high water mark to below low water mark. 

 This feature is present to a greater or less degree on every 



