231 



Springs are also good indicia of reversal of dip. Take for example 

 the occurrence of a porous bed overlying an impervious bed in an anti- 

 cline. Springs will be formed one each side of the anticline at the 

 point of contact of the porous bed with the impervious one. If the 

 anticline is a symmetrical one a chain of springs may occur at about 

 the same elevation on each side of the fold. If the anticline is unsym- 

 metrical the springs may occur at a higher elevation on one side than on 

 the other. 



Springs may also indicate the reversal of dip produced by the down- 

 throw of a block along a noi-mal fault. The springs will occur on the 

 banks of depressions following the general direction of the strike and 

 on the down-dip side of the outcrop. 



Fig. 4. Shows pool of water t'oinied on surface of dipping bed. Note position of 

 water level with reference to position of bedding planes on each side of pool. 



Surface of Pools. — The surface of pools of water in inclined strata 

 furnishes a horizontal plane by means of which even slight degrees of 

 dip may be recognized. The conditions most favorable to such observa- 

 tions are the presence of inclined beds of hard rock or alternate layers 

 of hard and soft rock which have been crossed by a stream in the bed 

 of which pools have been formed. Using the surface of the water in 

 the pool as a level, even slight dips may be detected by the diflPerence 

 in the elevation of the surface of the water upon layers oh opposite sides 

 of the pool. If the water stands on the uneroded surface of a hard 

 layer it will have greater depth on the down-dip side of the pool. 



Stream Channels. — The channels of dry streams are useful in de- 

 termining the direction of dip. In the case of a stream trending in a 

 line which is, in general, parallel with the strike and cutting across 

 hard layers or beds composed of alternate hard and soft layers the 



