JOURNAL OF PROCEEDINGS. 567 



from the whole description would seem to be, first, that the two lower 

 portions of this "Drift proper" correspond with the Pipe Clay and 

 Botilder formations of Prof. Swallow ; and second, that the reddish brown 

 clays (if not also some part of the buff and yellow clays), which form the 

 subsoil away from the streams, (containiig, probably, a greater or less 

 mixture of sand and other materials, and therefore, perhaps, more cor- 

 rectly called, in other parts of the volume, yellowish or chocolate brown 

 loam,) correspond with that yellowish or brown clayey loam which 

 underlies the true Loess where it exists, and (probably) covers the bluffs 

 and hills about St. Louis as well as the uplands and prairies of northern 

 Missouri, forming the subsoil away from the river valleys in Missouri in 

 the same manner as in Illinois, and which Prof. Swallow appears to 

 have included in his Loess. It is very clear that Mr. Worthen does not 

 suppose the Loess to extend over the higher uplands and prairies of Illi- 

 nois ; and if this be true of Illinois, it must be just as true of Missouri; 

 and the necessity for an inland lake of such immense extent must dis- 

 appear, though an expansion of the larger rivers so as to fill the valleys 

 in which they ran to the tops of the bluffs, and penetrate far up the 

 valleys of the tributary streams, would still have to be supposed. 



In the chapter on the " Origin and Formation of the Prairies," by 

 Leo Lesquereux (Geol. Stir, of Ills., p. 246), may be found a fine speci- 

 men of scientific reasoning upon this subject of the Prairies, which is at 

 once exhaustive and satisfactory. Mr. Lesquereux conceives the black 

 mould (which is half peat, half humus), and the immediate clayey sub- 

 soil of the prairies, to have been formed in shallow waters by the decay 

 and transformation of animal shells and vegetable matters, during the 

 process of slow emergence of the continent out of the ocean, after the 

 Champlain epoch of subsidence, and that the horizontal surfaces of the 

 prairies were thus successively left covered with vast sheets of shallow 

 water, in which the surface soil and mould of the prairies were gradually 

 formed and successively deposited. This deposit would, of course, be 

 made upon the brown clays and loam of the marine-drift period. Nor 

 would this theory imply the existence, at any one time, of a vast inland 

 fresh-water lake, extending over the whole area of the prairie country. 

 Nor does Mr. Lesquereux suppose that this kind of formation is confined to 

 fresh water only, but remarks that it is produced in the same manner in 

 the salt marshes of the sea as in the fresh-water swamps of our lakes. 

 But whether these sheets of water were salt, brackish, or fresh, they are 

 quite distinguishable from rivers, or river expansions from which the 

 true Loess was deposited; and they would be left covering separate 

 areas, at different times, as the sea gradually retired from the land, until 

 the surface drainage drew off the waters into the river valleys, forming 

 the river expansions at first, and at length the rivers. This may explain 

 how it happened that the Loess was limited to the river valleys, and 

 never extended to the upland prairies. 



In the yellowish or brown clay or loam which forms the compact mass 

 of the hills about St. Louis, no fresh-water and land shells are to be 

 iound. They have been searched for, many times, in the cuts of streets 

 and quarries, but never found, to my knowledge, in that clay or loam; 

 but they have often been found, in many places, along the bluffs of the 

 river on either side in deposits and remaining; patches of the true Loess, 

 overlying this brown clay or loam. It would seem to be very question- 

 able, whether this brown clay or loam, containing no shells, is not a part 

 of the marine drift proper, deposited in the river valleys before the 

 present rivers ran in them (and apparently not included in Prof. Swallow's 

 Altered Drift), and, more probable, if not quite certain, that it is no part 

 of the fresh-water drift or Loess. 



The Illinois survey states that the Blue Clays at the base of the Drift 

 contain fragments of wood and trunks of trees, but no fossil remains of 

 animals; but that the brown clays above, underlying the Loess, contain 

 remains of the Mammoth, the Mastodon, and the Peccary, and that bones 



