36 PHYSICAL GEOGKAPHY. 



reason to believe that the surface deposits received their 

 positions independently of any folds of the strata, and that 

 they have not since been disturbed by folding. It is worthy 

 of remark in this connection that the general course of the 

 streams of the eastern system — these having more generally 

 reached the underlying strata than those of the western sys- 

 tem — coincides very nearly with the trend of the outcrop of 

 the formations along or upon which they run. Possibly, 

 some of these eastern streams received their initial direction 

 by longitudinal depression left in the surface of the drift, 

 consequent upon the greater or less facility with which they 

 were respectively eroded along the lines of their outcrop 

 during the Drift epoch. 



The eastern drainage system comprises not far from two- 

 thirds of the entire surface of the State, and is more complete 

 in itself than the western system, because its rivers are larger 

 and have the principal part of their courses within the State; 

 while a large part of the area occupied by the western system 

 is drained by the upper branches of streams that constitute 

 a large pa,rt of the drainage system of the State of Missouri. 

 An interesting feature of the division of these two systems 

 consists in the peculiar character of the Great Watershed, or 

 that which divides the drainage between the two great rivers. 

 This watershed is formed by the highest land between those 

 rivers along the whole length of a line running southward 

 from a point on the northern boundary line of the State near 

 Spirit lake, in Dickinson county, to a nearly central point in 

 the northern part of Adair county.* 



From the last named point, this highest ridge of land, 



* Preliminary railroad levelings along the western part of the line of the Chicago 

 and Northwestern Railway, show that at a few points along the secondary watershed 

 between Boyer and Soldier rivers, the elevation is actually greater than that of the 

 Great Watershed where the railway crosses it. This may have resulted from a greater 

 erosion of the Surface Deposits at that point than at others, both along the Great 

 Watershed, and along the upper portion of the secondary watershed just named; or, it 

 maybe, that the Bluff Deposit which constitutes that secondary watershed, was origin- 

 ally so accumulated, that its surface actually occupied a higher level than the surface 

 of the Drift Deposit did further eastward. This subject is again referred to under the 

 head of Bluff Deposit in the chapter on Surface Deposits. 



