Mesozoic and Camozoic Geology and Palaeontology. 319 



ceaseless agency of water, not sweeping over the surface in the might\^ 

 currents of the diluvial epoch, bearing the detritus of northern crys- 

 talline rocks, and grinding down and bearing away the softer strata, 

 but falling as rain, percolating through the calcareous and magnesian 

 deposits, and graduall}^ carrying them off in solution, leaving the in- 

 soluble portion behind, in the form in which we now see it covering 

 the solid rock, as an intimate mixture of the finest argillaceous and 

 silicious particles. 



The trunks and branches of coniferous trees, belonging, apparently, 

 to existing species, are quite common in the blue clays at the base of 

 the drift ; and in the brown clays above, the remains of the mammoth, 

 the mastodon, and the peccarj' are occasionally met with. The fine 

 fragment of a mastodon's jaw, with the teeth, found at Alton, was ob- 

 tained from a bed of drift, underlying the loess of the bluffs, which, at 

 this point, was about thirty feet thick, and remained in situ above the 

 bed from which the fossils were taken. Stone axes and flint spear- 

 heads are also found in the same horizon, indicating that the human 

 race was cotemporary with the extinct mammalia of this period. The 

 bones and teeth of a great number of species are found in the crevices 

 of the rocks in the driftless area of the lead region, where they have 

 been washed from the surface, and carried in some instances fifty or 

 sixt}' feet before finding a lodgment. The most abundant among the' 

 remains of animals thus found are those of the mastodon, whose teeth 

 and bones have been procured from a great number of crevices, over 

 the whole ai-ea of the lead region ; showing that the species must have 

 lived and flourished in immense numbers, and through a long period of 

 time, since the chances of the preservation of the remains of any one 

 individual b}' being washed into a crevice, must have been exceedingly' 

 small. The remains of both living and extinct species are found in the 

 crevices in such positions, in reference to each other, as to indicate 

 prett}' clearly that they were living together. From a crevice, near the 

 Blue Mounds, Prof, Worthen collected the bones and teeth of the masto- 

 don, peccary, buffalo, and wolf — the two former extinct, and the two 

 latter supposed t-o be identical with the living species. 



In 1867, Prof, C. A, White* found drift scratches upon limestone of 

 the Upper Coal Measures, in Mills county, Iowa, near the Missouri 

 river, having a direction S. 20° E., and these crossed by a finer set of 

 scratches, having a direction S. 51° E. And at an exposure of the 

 same limestone, one mile below Omaha, the capital of Nebraska, imme- 



■■' Am. Jour. Sci. and Arts, 2d series, vol. xliii. 



