THE RIVER SYSTEM OF CONNECTICUT 473 



the resultant of which acted in a direction normal to the axis of 

 Green Mountain folding (N. ± 8o° W.), stresses which were 

 relieved by dislocation along the planes of maximum shear, 

 approximately 45° to either side of the direction of pressure, 

 i. e., S. ± 55° W. (N. ± 55° E.) and N. ± 34° W. The remain- 

 ing common directions of fault planes (N. ±: 15° E. and N. ± 

 5° W.) could be explained by a subsequent development of 

 compressive stress acting along the initial direction ; for in a 

 region containing planes of separation at 45° to the direction of 

 pressure, there would be a resolution of the stress into compo- 

 nents acting along the planes of separation and along that diag- 

 onal of the blocks which is nearly normal to the pressure. The 

 direction N. ± 15° E. corresponds to this diagonal of the joint 

 block already formed, and the remaining direction N. ± 5"^ W. 

 is the corresponding diagonal of two such blocks in contact. To 

 explain these latter dislocations upon the same principle, it must 

 be assumed that, owing to differences between the alternate joint 

 planes of the same series, these double joint blocks acted to 

 some extent as units. The fault directions characteristic espe- 

 cially of the southern portion of the area and disclosing such 

 intimate relationships to the four generally prevalent ones, might 

 be explained either by assuming that in the later compression of 

 the jointed area composite blocks of different shapes, because 

 composed of a different number or different arrangement of unit 

 blocks, acted as units (whether due to the greater perfection of 

 their bounding fault planes over intermediate ones, to the par- 

 tial closing or healing of the intermediate faults, or to some 

 other cause). In this case the maximum shear would be along 

 the diagonal of the composite blocks, as would be the case in 

 the unit blocks themselves, and it is shown in the report under 

 review that these directions do correspond, tiot only i?i direction, 

 but also in positioti with the diagonals of important composite 

 blocks of the area. Under certain conditions, which may or may 

 not have obtained in the area, planes of dislocation having the 

 same directions might have been produced through the depres- 

 sion of the composite blocks subsequent to the jointing of the 



