178 NEW YORK STATE MUSEUM 



Let US now take the evidence this pebble has to offer con- 

 cerning the question of cave formation. As it has rested at a 

 level close to that of the floors of many of these caves for just 

 as long a time as Lake Champlain has been in existence, it 

 should be able to offer a fair measure of this lake's capacity to 

 dissolve its limestones and to erode them through dentpit 

 formation. At Cystid point these two agencies have cut com- 

 paratively pure limestones to the depth of but 27 millimeters. 

 It does not seem likely that the deeper purer waters of Para- 

 dise bay could, in a more sheltered position, have cut to greater 

 depths during the same period. Many of the caves of this region, 

 however, represent a cutting more than 75 times as wide and 

 several hundred times as deep. Portions of their walls are out 

 of water for more than half of each year and are then free from 

 any action of this nature, but the pebble has remained under 

 water for every moment of every year. The results of this 

 comparison are very striking and perhaps are not wholly fair. 

 It may be urged that vortex action would be stronger and there- 

 fore more effective in shallower waters. This may be true, but 

 the greater depths of the caves have also been subjected to this 

 action for every moment of every year and under this depth 

 we shall probably be again dealing with vortexes whose strength 

 is no greater than those of the pebbles' level at Cystid point. 

 Most of the cave walls maintain their wedgelike shape and be- 

 come wider as the limit of low water is reached. Weighing 

 carefully the evidence, we shall make ample allowance for the 

 results of these two features of wall cutting if we credit them with 

 the removal of between 2 and 4 centimeters of surface during the 

 age of the present lake. The evidence of the pebble is therefore 

 to the effect that Lake Champlain has been at most but a modifier 

 O'f a belt of old caves which were very .evidently left here by an 

 ancestral body of water. 



Valuable as has been the evidence this specimen has given us, 

 it has yet failed to show that for which it was taken from its 

 position of long rest. In other words it has failed to clearly show 

 the amount of solution accomplished by the present lake. 

 We have merely found a very definite limit which solution could 

 not have reached in the time involved. It should be allowable 

 however, and helpful as well, to make an approximate or tentative 

 estimate of the share each agent has accomplished in this recorded 

 work. As a whole, abrasion is a much more powerful agent than 



