750 T. C. CHAM BERLIN 



July, 1883, and have been buried in alluvium as deeply as the 

 Lansing skeleton by August 18, only twenty-one days later. 

 Without doubt, within a few years it would be covered by sixty 

 feet of alluvium through the migration of the channel of the 

 river. 



2. The prevale?ice of this profound reworking. — To illustrate 

 how fully and effectually the whole of the bottoms of the Mis- 

 souri river in this region are involved in its meanders and their 

 shiftings, and how its bordering bluffs are being forced to retire 

 by the impingement of the currents at its bends, a reduced copy 

 of the United States Engineers' map is here introduced (Fig. 3), 

 the section being about forty miles north of the locality in ques- 

 tion, but representative of the conditions in all this portion of 

 the river. It will be noted that practically the whole valley 

 bottom is involved in the migrating loops, and that every part of 

 its silt bed is liable to be disturbed again and again by scour 

 and redeposit ; indeed, it is probable that this has happened 

 repeatedly to many portions, if not to most portions of the 

 alluvial filling. It is perhaps not greatly beyond the facts to 

 regard the whole bottom filling as being shifted, step by step 

 down stream by successive scour and fill. This is more espe- 

 cially true of the borders of the bottom filling next the bluffs 

 where the arrest and turn-about of the powerful stream gives 

 the greatest rotatory and deep-disturbing effects. 



3. The absence of the great Dakota system of terraces. — In the 

 widening of the bottoms thus still in progress doubtless lies the 

 reason why so few distinct remnants of the grand systems of 

 glacial terraces and glacio-fluvial deposits of Dakota, described 

 by Todd, 1 are found in this lower portion of the Missouri river. 

 It is probable that the whole tract once occupied by these, and 

 more besides, is now embraced by this widened, and still widen- 

 ing, zone of lateral encroachment. This is the less remarkable 

 when we recall that the Missouri river was formed by the union 

 of many preglacial streams of various connections whose lower 

 courses were blocked up by the ice invasion so that they were 



1 Loc. cit., pp. 128-140. The general nature of these is given in a later portion of 

 the present paper. 



