638 CHARLES EMERSON PEET 



great range of the upper series of terraces has not been found. 

 But if the ice was present on the Bouquet River when Higher Glacial 

 Lake Champlain was inaugurated, there was time for the cutting 

 down of the outlet as it retreated northward, and thus it would be 

 expected that the terraces at the Bouquet River would have a greater 

 range than northward where the uppermost wave-wrought terrace 

 was not made until after the uppermost Bouquet terrace was com- 

 pleted. The failure of the terraces to show a greater range at this 

 point (latitude of the delta on the Bouquet River) than farther north 

 would indicate, either that the outlet was being cut very slowly, or 

 that the water-level was being maintained at the north in some way, 

 as the ice retreated from the Bouquet deltas. It is possible that uplift 

 of the outlet maintained the water-level, or even caused it to rise in 

 the northern part of the basin as the ice retreated, thus causing as 

 great a range of terraces farther north as on the Bouquet River. 

 The fact that the upper wave-wrought terrace near Whallons- 

 burg is 30 feet higher than the surface of the Bouquet deltas 

 would suggest that this tipping northward had been more than 

 sufficient to overcome the effect of the cutting of the outlet as the ice 

 was retreating, and that the water-level had actually been made to 

 rise higher than its level when these deltas were made in the pres- 

 ence of the ice. If this explanation be correct, then at the south 

 only, where the uplift of the outlet end of the basin could not main- 

 tain the water-level on the sides of the basin, would the range of the 

 terraces be such as the cutting of the outlet alone would produce. 

 Later, when the water-level began to fall throughout the basin, the 

 ice had retired north of the Saranac River, and the range of ter- 

 races here seems to indicate that a differential northern uplift had 

 begun. 



Another interpretation. — The above has been written on the as- 

 sumption that either the 5 80- foot Ausable, or the 640- foot Saranac 

 gravel plateau, or both of them, are deltas made in the presence of 

 the ice, and that the 500-foot Ausable and 520-540-foot Saranac deltas 

 are the later product of erosion of the higher gravels. If it should 

 be found that neither the 580-foot Ausable nor the 640-foot Saranac 

 deposits are glacial deltas, but that the 500-foot Ausable and the 

 5 20-540- foot Saranac deltas are the highest, and if also some of the 



