VALLEY REGION ; ORIGIN OF THE ROCKS. 141 
many reasons for the conclusion that the force in question 
came from the southeast rather than from the northwest, one 
of these reasons among many, as already said, being that 
‘the intensity of the disturbance constantly diminishes as we 
go from southeast to northwest. 
The varying degree of deformation of the strata by vary- 
ing amounts of compression can be imitated on a small 
scale and illustrated by pressing together sheets of cloth of 
clay or other plastic material. 
If we place on a table a number of sheets of flexible cloth 
piled one upon the other like the sheets in a pad of paper, 
and fixing one edge of this pad, push or slide along the table 
the opposite edge towards the fixed edge, we shall see that 
a number of wrinkles will be at once formed across the 
sheets of cloth at right angles to the direction of the com- 
pression. If we continue to press the edges of the sheets 
towards each other, the arches will rise higher and higher, 
and begin to lap over in one direction, which, in the majority 
of cases, will be the direction towards which the shoving 
force acts. In a few cases the troughs will be shoved under 
the arches and the folds will lap over in the opposite 
direction. 
Now, if we study closely the folds or wrinkles into which 
the strataof the region about which we are now writing have 
been thrown, we may easily recognize the very same arrange- 
‘ment. There are simple folds or arches, with almost equal 
slope on each side of the crest line, but these are rare; 
there are folds in which the arches have been pushed over 
towards the northwest, making the slope on that side 
steeper than on the southeast, these are very common; 
there are folds which have been pressed together so that 
the two sides are about parallel, and then lapped over to 
the northwest, these are also very common. On the other 
hand we find folds in which the troughs have been shoved 
under the arches so as to cause the steeper slope to be on 
the southeast side, and when this movement has gone on far 
enough the arches have the appearance of having been lap- 
ped together and pushed over towards the southeast by a 
force acting from the northwest; these cases are by no means 
so common as the others, yet we see in Murphree’s Valley 
