SIXTH REPORT OF THE DIRECTOR I909 181 



removed more than a very few millimeters of this surface. Now 

 the periods of time involved in the cutting of the dentpits, the 

 softer layers of the pebble from Cystid point, and the softer layers 

 of the rock shelf here are practically equal, for the phenomena 

 occur along the same horizon. Wihen once the waters of Lake 

 Champlain had reached their present level it would not take shov- 

 ing blocks of ice very long to clean off the Sloop bay shores and 

 leave them very much as we now find them. The amount of rock 

 surface removed by the solvent action of the incessantly changing, 

 and far from saturated, waters of Lake Champlain is shown by 

 these studies to have been remarkably small. 



A still more conclusive bit of evidence concerning solution is to 

 be found along the more southern portion of the west shore of 

 the island. There is a line of low cliffs along a considerable portion 

 of this shore, and it often rises several meters above low water. 

 These surfaces are exposed to wave action from seas raised by 

 westerly winds. Such waves here carry little sediment owing to the 

 deep water and clean rock bottom just off shore. That these waters 

 are deep is indicated by the presence of the ruins of an old dock here 

 at which the largest lake steamers used to stop to take on wood in 

 the days when that was the available fuel. A view of this 

 region is shown in plate i8. The long oval rock basin of the fore- 

 ground, considerably foreshortened in our view, is but one of a 

 number of such basins cut ,by the till on the old shore line of Lake 

 Valcour. The debris seen in the basin has been derived from 

 higher portions of the shore line through the effects of freezing 

 water in joints and bedding planes, and the action of shore ice. The 

 amount of the destructive work of Lake Champlain on this older 

 glaciated shore line may be easily seen. The principal, and by far 

 the greatest cause of loss, has been due to the effects of freezing 

 water in joints and bedding planes and the subsequent removal 

 of the loosened blocks through the action of shore ice. The ma- 

 terial now lodged in the glaciated basin is a portion of the material 

 which was so derived from the surface above. Wave action itself, 

 even with the load of tools here present, has been rather an unim- 

 portant agent and has not been able to modify appreciably the basin 

 in question. A nearly complete portion of an old glaciated outline 

 of this ancient coast may be seen where the figure is present. One 

 block has been removed from the surface on which she is standing 

 but much of the old glaciated surface remains above and to the 

 right of her head. The shelf on which the boat rests has been 



