.\rGEE NOTES ON THE GEOLOGY OF MACON CO., MO. 313 



the birth of the waterways. Yet the surface of this vast plain 

 could not have been absolutely horizontal when the drainage was 

 first determined, since the parallelism of the streams is confined 

 to comparatively limited tracts, and the direction of drainage in 

 contiguous tracts is not coincident. The remarkable parallelism 

 of the drainage in Missouri, shown in Fig. 2, suggests that on the 

 west side of the "grand divide" there was a decided slope south- 

 ward, and on the east side nearl}^ as decided a slope southeastward 

 when the waterways originally extended themselves over the sur- 

 face. 



THE SUPERFICIAL DEPOSITS. 



Alluvium. — So far as can be determined from exposures in 

 stream channels, the smaller runnels, and the few artificial exca- 

 vations examined, the valleys of Salt river and East Fork, as well 

 as those of the more important tributaries, are lined with water- 

 laid deposits extending from bluft^to bluft^, and forming a sensibly 

 level floor, generally wooded densely, and little diversified by 

 abandoned channels or other irregularities. The maximum depth 

 of this deposit was not ascertained ; but since the channels were 

 dry (except in the deeper pools) at the time of examination, it 

 was found that the streams have occasionally cut through it and 

 into the drift or the subjacent rocks ; and it may be inferred 

 hence that the average depth is little greater than that of the river 

 channels — i.e. some 15 or 20 feet. 



The fluvial deposits of the principal streams exhibit two gener- 

 ally distinct phases, the first and more important consisting ot 

 massive or rather obscurely laminated brown clay or sand, 

 while the second and subordinate phase is made up of irregularly 

 arranged and heterogeneous loam, sand, and gravel, with occa- 

 sional intercalated vegetal layers. The brown clay is unlike, but 

 the more heterogeneous deposits are like, the deposits now laid 

 down by the streams ; the latter are evidently derived from the 

 adjacent drift and indurated rocks, while the former is as evi- 

 dently derived from some other source ; and, where both occur in 

 the same exposure, the sands and gravels rest upon the clay. 

 The alluvium of the tributaries is generally identical with the 

 superior heterogeneous phase of the deposits as found along the 

 rivers. It is noteworthy that in this as in all other regions of 

 growing autogenetic drainage the s.naller streams and ravines are 



