8 The American Geologist. July, i897 
angles to the axis of the monocline. Although the dips in 
this locality are very confusing, the fold may be readily 
traced to the northwest, leaving 9 N., 17 W., at the west line 
of section 6, south of White Oak mountain. At this place the 
strata have southward dips of 15-20 degrees. Prom this 
point westward to its western terminus the fold is parallel to 
the south face of the Boston mountains, the axis being close 
to the mountain escarpment which is very prominent every- 
where from White Oak mountain in 10 N., 18 W,. to Mulberry 
mountain in 10 N., 20 W. 
From south of White Oak mountain the monocline extends to 
the northwest to the west side of 10 N., 18 W., where in sec- 
tions 18 and 19. south and southwest dips, at some places 20 
degrees, are to be seen. The direction of the fold from the 
west sid? of 10 N., 18 W., is slightly south of west for six 
miles, the dips ranging from 10-20 degrees, southward. From 
the northwest quarter of section 30 it turns directly to the 
northwest, striking the west range line of 10 N.. 20 W., in 
section 7, from which point it continues in a direction slight- 
ly north of west to 11 N., 21 W., section 30, the southwest 
quarter, where it turns to an almost west direction which it 
continues to 11 N., 21 W., section 30, the southwest quarter, 
where the rocks dip 15-20 degrees south. Here the fold 
turns again to the southwestward around the south base of 
Mulberry mountain and has its western terminus at a distinct 
fold just south of the western end of that mountain in 10 N., 
26 W. 
The axis of this line of disturbance is, in a general way, 
parallel to the principal axes of folding in the mountains be- 
tween it and the north side of the Ouachita uplift. 
Effects upon Drainage and Topograph//. One of the most 
noticeable features of the Red River monocline is its effect 
upon the drainage and topography of the country through 
which it passes.^ Owing to the slight resistance offered to 
erosion along the line of disturbance the streams have cut out 
deep valleys parallel to it. The axis of the fold is always 
found a short distance (from one-half mile to one mile) to 
the north of the present location of the streams, which are in 
the south dipping rocks. The original course of the streams 
must have been in each case at the axis of the fold or where 
