308 TRANS. ST. LOUIS ACAD. SCIENCE. 



tinctive t)pes of drainage, the ''grand divide" is in no respect 

 specially noteworthy or distinguishable on the ground from its 

 scarcely lower analogues on the east and west, beyond Salt river 

 and the East Fork of the Chariton respectively. 



As its local designation certainly does not imply, the ''grand 

 divide" is simply a broad and remarkably smooth and level plain 

 extending from the immediate blutis of Salt river to within a mile 

 or two of the East Fork, scalloped and ravined by secondaiy 

 drainage along its margins, but imperfectly drained interiorly. 

 Its altitude at Macon, where it is somewhat broken by ctoss- 

 drainage, is about S90 feet, and it inclines southward gently to 

 866 feet at Excello, and 5 feet less at Jacksonville,* just south of 

 the county line, at both of which points the divide exhibits its 

 normal aspect — i.e. a smooth, monotonous, sensibly horizontal,, 

 and imperfectly drained plain. 



The divide between the East Fork and the Middle Fork (of the 

 Chariton) is a similar plain, ravined along its margins but level 

 and imperfectly drained within, of almost exactly the same alti- 

 tude as the principal divide, and, like it, inclining gently south- 

 ward. The Middle Fork, which bounds it on the west, is however 

 deeper than Salt river, giving this plain the greater average 

 height above its base level ; and thus it is more deeply scalloped 

 and more profoundly broken along its margins than the "grand 

 divide." Moreover, it is noteworthy that both Salt river and East 

 Fork generally approach the western sides of their valleys, and 

 that the blufis on this side are steeper than on the east ; and sa 

 the eastern margin of the lesser divide is more steeply bluffed 

 than the western margin of the "grand divide." 



East of Salt river the surface quickly rises as on the west, and 

 in like manner assumes the form of a level, uniform plain — "Crip- 

 pen's prairie" — which extends eastward far into Shelby county^ 

 and is only slightly incised by the south-flowing Salt river tribu- 

 taries. This plateau is only a few feet lower than the "grand 

 divide," and slopes so gently southeastward that the inclination 

 is imperceptible, except by comparison of altitudes at widely 

 separated points. 



* Gannett, Dictionary of Altitudes, Bull. U. S. Geol. Snrvey, vol. i. No. 5, 18S4. 



