REPEATING PATTERNS IN THE EARTH RELIEF 227 



the lines of drainage; for where the pattern is not completely 

 closed by the course of the stream, there is generally found either 

 a dry valley or a ravine to complete the design. If these are 

 not present, a bit of straight coast line, a visible line of frac- 

 ture, a zone of fault breccia, or the boundary line separating 

 different formations may one or more of them fill in the gaps of 

 the parallel straight drainage lines which by their intersection 

 bring out the pattern. These significant lines of landscapes 

 which reveal the hidden architecture of the rock basement are 

 described as lineaments (Fig. 82, p. 87). They are the character 

 lines of the earth's physiognomy. 



It is important to emphasize the essentially composite ex- 

 pression of the lineament. At one locality it appears as a drain- 

 age line, a little farther on it maybe a line of coast; then, again, 

 it is a series of aligned waterfalls, a visible fault trace, or a recti- 

 linear boundary between formations ; but in every case it is some 

 surface expression of a buried fracture. Hidden as they so gen- 

 erally are, the fracture lines must be searched out by every means 

 at our disposal, if we are not to be misled in accounting for the 

 positions and the attitudes of disturbed rock masses. 



As we have learned, during earthquake shocks, as at no other 

 time, the surface of the earth is so sensitized as to betray the 

 position of its buried fractures. As the boundaries of orographic 

 blocks, certain of the fractures are at such times the seats of 

 especially heavy vibrations; they are the seismotectonic lines 

 of the earthquake province. Many lineaments are identical 

 with seismotectonic lines, and they therefore afford a means of 

 to some extent determining in advance the lines of greatest daiv 

 ger from earthquake shock. 



The composite repeating patterns of the higher orders. Not 

 only do the larger joint blocks become impressed upon the earth 

 relief as repeating diaper patterns, but larger and still larger com- 

 posite units of the same type may, in favorable districts, be found 

 to present the same characters. Attention has already been 

 more than once directed to the fact that the more perfect and 

 prominent fracture planes recur among the joints of any series at 

 more or less regular intervals (Fig. 40, p. 57, and Fig. 41, p. 58). 

 Nowhere, perhaps, is this larger order of the repeating pattern 

 more perfectly exemplified than in some recent deposits in the 



