DRA IN A GE MODIFICA TJONS 5 8 1 



to mii^Tatc away from its axis; and will continue in that direc- 

 tion until the streams attain a condition of equilibrium. 



The migration of the divide away from the axis of depres- 

 sion generally results in the formation of a stream along the 

 axial line ; and the direction in which it flows will depend, in 

 a great measure, upon the pitch of the axis of the fold. 



Such is the law of the migration of divides, under the influ- 

 ence of surface warpings. It is probable that if such migra- 

 tions have occurred in the past we can find some trace of the 

 modifications thus produced and be able to determine the char- 

 acter, direction and extent of the movements, and from that 

 form some idea of the physical condition of the continent in 

 late periods of geologic history.' 



Marius R. Campbell. 

 U. S. Geological Survey. 



'To be followed by Part II, Criteria for Determining Stream Modifications. 



