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Show :Figure 64.-Scction across a simple fault. Figure 65.-Sinctcot lon .a cro118 a f au It with walls widely eeparato<l tlu, rvemng space filled with broken rocks. ' FAULTS. 183 of this fracture should drop down many hundreds of feet. Now, to go from the low lands to the high lands it would be necessary to climb a great wall. We must conceive this line to be a somewhat meandering one, so that the wall is turned more or less from a direct course. Again, the throw of the beds is variable, being greater or lesser here and there along the faultin some places, but two or three hundred feet, perhaps; in others, two or three thousand. For tllis reason the altitude of the cliffs is greatly variable. Again, the brink, or edge, of the irregular wall has tumbled down in many places, leaving pinnacles, towers, and crags hero and there; and below may be seen a great talus, whel'e the rocks which have tumbled down are piled against the foot of the wall. Then there are streams heading in the upper country, and running down into the lower, which have cut for themselves channels-narrow gulches, or, perhaps, in some places, narrow valleys, so that we have, not a vast, unbroken wall, but an irregular line of cliffs. Let us turn our attention to these faults, and the topographic features to which they give rise. Sometimes we find that the beds are broken by a well defined fracture, and the plane of separation between the beds which have dropped down and tho e which have remained in place is clearly marked. Figure 64 is designed to represent a section across such a fault, where the bed a, a on the left is seen to lie at a higher level than on the right. Sometimes the fault branches, and the throw, or displacement, occurs along two or more lines, so that a great step may be broken into two or more smaller ones, as represented in Figure 69, whore the bed a, a is seen in each step. In other places, the beds have fallen down without obstruction for a part of the distance, and have been caught and turned up, as in Figure 71. In many places we find no definite line of separation between the strata in place and the fallen strata, and there is a space of greater or lesser extent, sometimes several hundred feet wide, between the two series, composed of fragments of the same rocks, in some cases. thrown down promiscuously, and found much mixed, as seen in Figure 65; hut in others, preserving, in :tn irregular, broken way, the stratification, by a flexure, from the upper to the lower beds, as seen in Figure 66, wh re the rocks seem to have been torn asunder by the stretching they received in displacement. Again, we find the rocks intervening between the horizontal beds |