66 



system is the oldest, and most general, the S.W. system the most recent 

 and most marked and sudden system. 



The writer would, in conclusion, ask one further question about 

 these faults. 



Can it in anyway be determined, by examining their peculiarities, 

 by what kind of force they have been formed. 



Now there are three ways in which faults may have been made. 



1. By a force thrusting up a portion of the earth's crust. 



2. By the interior of the earth cooling down and contracting, and 

 so the surface falling in. 



3. By an undulation of the surface of the earth such as is 

 experienced in the case of the waves of earthquakes. 



Now these three classes may be easily illustrated in diagrams, 

 and it will be at once seen that the thrusting force is the one which 

 corresponds with the general rule of the miners that a fault is nearer 

 " back over." 



If faults be produced by subsidence of surface then it must (in order 

 to maintain this rule) be always accompanied by a corresponding 

 elevation beyond. 



And this may lead us to what must be at present a mere conjecture 

 as to the origin of these systems of faults, viz. — 



That West Cumberland has at different times been subject to two 

 main earth-waves. The one running N.E. and S.W. (producing the 

 N.W. system of faults) which was more general, gradual, and probably 

 older, the other running about NN.W. and SS.E., which was more 

 partial sudden and probably more modern : both however occurred 

 after the formation of the New Red Sandstone Rock. 



