QUARTZITE TONGUE AT REPUBLIC, MICH. 69 1 



above the neutral surface yielded to the compression, in part, by 

 slipping along the bedding planes. If for any reason such 

 movement could take place more easily along any one surface, 

 the neighboring surfaces would be relieved, and one of maximum 

 movement would result. It is readily conceivable that in the 

 same way one local maximum might relieve several neighboring 

 maxima, and so a large amount of movement might be accumu- 

 lated along a single surface. A maximum movement, starting 

 in the specular jasper would, on account of the slight upward 

 convergence of dip, necessarily tend to cut across the quartzite 

 at the contact. The quartzite might be traversed until a surface 

 of maximum movement in it was reached, which would then be 

 followed. The result would be a fault, along which the material 

 on the side towards the interior of the trough would be dis- 

 placed relatively upwards, and which, in the direction of the 

 strike, might easily pass from one rock to the other more than 

 once. The wedge of specular jasper included between the sur- 

 face of movement and the contact surface would move relatively 

 upward with the main body of quartzite, while the corre- 

 sponding wedge of quartzite above the line along which the con- 

 tact surface was traversed would remain relatively at rest with 

 the main mass of jasper. 



A break formed under such conditions, accompanied by 

 displacement sufficient to bring these two wedges together, and 

 followed by sufficient denudation, would result in the surface 

 relations that may now be observed on Republic Mountain. 



Henry Lloyd Smyth. 



Cambridge, Mass. 



