372 Ohamberlin and Salisbury — Relationship of 



Were the gravels and sands of the Orange Sand series to be 

 referred to the first episode of the first glacial epoch, their 

 origin should be revealed by their constitution, if glacial waters 

 were the depositing agent. In this case we should confident!} 7 

 expect to find pebbles of northern origin among these gravels. 

 It would not be necessary to suppose that all the gravel 

 deposited by a stream springing from the glacier would neces- 

 sarily be northern, since tributaries might bring in material 

 from other directions, in the ordinary process of river degra- 

 dation. But emphasize the importance of this latter considera- 

 tion as we may, it yet remains an indisputable fact, that, were 

 the conditions of drainage such that tributaries could bring 

 gravel to their main in great quantities, the main itself, if 

 springing from the ice, would inevitably bring something of 

 glacial debris, which would be found mixed with the material 

 of more local origin, brought in by the tributaries. And this 

 would be true, even if the accumulation took place at an 

 earlier stage of the glaciation of the first episode, long before 

 the ice approached the latitudes under consideration ; for the 

 drainage basin of the Mississippi reaches several hundred miles 

 to the northward, and probably extended still farther in that 

 direction at an early stage of the ice invasion, when the ice had 

 so far spread itself over the British possessions as to prevent 

 drainage into Hudson's Bay. 



If then, the Orange sands and gravels were accumulated 

 during the first glaciation of the first glacial epoch, as valley 

 or estuary deposits, we should of necessity have northern 

 material represented in this formation, if not in the form of 

 sands and gravels, at least in the form of silt. Such, however, 

 is not the fact. In the hundreds of exposures of gravel 

 which the writers have seen, large numbers of which, in 

 various localities in six states, have been examined in detail for 

 this especial purpose, not a single pebble of demonstrably 

 northern or glacial origin has ever been found. Northern peb- 

 bles have been found associated with pebbles derived from the 

 gravels under consideration, but only in such situations that 

 the secondary character of the deposits containing such peb- 

 bles, was certain or altogether probable, from considerations 

 entirely independent of those here adduced. And the free- 

 dom from glacial gravel and sand and silt does not characterize 

 the Orange sands simply in their most southern distribution, 

 where the local material might naturally be more abundant 

 than to the north, but even up to the northern limit of the 

 Orange Sand region, scarcely more than a score of miles from 

 the southern border of the glacial drift, the northern or glacial 

 materials are likewise altogether absent. 



