LOESS WITH HORIZONTAL SHEARING PLANES 249 
stylolitic joints or of glacial fluting. There is no doubt whatever 
in my mind that these partings represent shearing planes and that 
they have been produced by differential motion of the layers which they 
separate. 
What may have caused such shearing is a question difficult 
to answer. Local creeping appears to be the least far-fetched 
explanation. On steep and high slopes the ground sometimes 
slowly yields to gravity and moves forward and downward on an 
inclined plane. The horizontal ingredient in such motion is 
more or less vertical to the ‘‘strike’’ of the slope. Observations 
on the trend of these flutings soon brought out the fact that this 
bore no relation whatever to local or minor topographic features. 
Their direction maintains itself with only small variations for 
short distances, and at some places, apparently for miles, irre- 
spective of local topography. Thus at Council Bluffs, in Kane 
township, in Norwalk, Booner, and Neola townships, the bear- 
ings of the flutings are respectively 60°, 65°, 70°, and 75° west 
of south and east of north. At the latter place, near Neola, it 
is variable, 70°, 75°, 78° west of south and east of north having 
been noted within a distance of twenty rods in the west part of 
the village. East of the town it is 10° north of west. For the 
next five miles east this direction prevails, three points show- 
ing a trend of 8°, 5°, and 20° north of west, all in Minden town- 
ship. East of this the trend is again to the southwest, except 
at a point three miles northeast of Avoca, where it is west 45° 
north and east 45° south. On opposite sides of a hill or of a 
valley, it seems from some observations that the direction is the 
same, whether it be parallel, vertical, or at any other angle with 
the local relief contours. 
The general trend of the flutings may be said to be from the 
northeast to southwest. This generalization is based on obser: 
vations made at only fifteen localities, which are scattered over 
a territory thirty-six miles from west to east and fifteen miles 
from north to south. This seems an insecure and insufficient 
basis from which to draw the conclusion that the flutings have 
been produced by general movements of the loess in the direc- 
