DRAINAGE MODIFICATIONS 



66 1 



adjust themselves in a direction perpendicular to the course of the 

 small streams ; so the final result will be an arrangement of the 

 drainage similar to that which occurs when the uplift is in any 

 other position. 



[b) Unsyni)}ictncal drainage basins. — When the tilting affects a 

 territory broad enough to include several systems of greater or 

 less extent, a peculiar arrangement is produced which can be 



P'lG. II. 



easily recognized, and which shows at a glance the direction of 

 the tilt which produced it. The minor drainage lines, as just 

 described, will arrange themselves in general lines at right angles 

 to the axis of uplift, and will unite in trunk streams parallel to 

 the rising fold. Figure 1 1 represents the drainage on such a 

 broadly tilted surface. The axis is indicated by the line XF. 

 The territory is divided among the streams A B C, A D G, and 

 H I J. It is but reasonable to suppose that before the tilting 

 occurred, these streams were in about the center of their respec- 

 tive basins. As the land rose along the line X V the minor 

 branches on the right-hand side of the larger streams were 

 retarded by the uplift, whereas the branches on the left were 

 accelerated. These accelerated streams crowded the divides 

 farther and farther up the slope and at the same time extended 



