882 STUDIES FOR STUDENTS 



tion as the number of observed faults is large. It has been 

 observed in the Pomperaug valley and fully confirmed by expe- 

 rience gained subsequent to the publication of the report upon 

 that area, that a regular spacing of normal faults is as character- 

 istic of them as it is of joints. It is, therefore, often possible to 

 determine not only the shape but the size of orographic blocks 

 included between series of normal faults within a system or 

 network. 



2. Observed faults are parallel to the joint system. — In this 

 observation lies the most important evidence that the region as 

 a whole is affected by a system of normal faults genetically 

 connected with its system of joints. Not only is it to be 

 observed whether the two systems are parallel, but, if so, it is to 

 be noted whether any simple relation connects the direction of 

 the individual joint and fault series with the dimensions of the 

 orographic blocks which they have conditioned. 



3. Zigzag topography. — The study of the topographic map 

 supplemented by observation and by photographs made in the 

 field may show that the physiographic features are bounded by 

 straight elements which coincide in direction with the network 

 determined by the joints and faults. Figs. 9 and 10 represent 

 topography of this type, the one from the intricately faulted 

 Newark area near Meriden, Conn., the other from the crystalline 

 belt of Berkshire county, Mass. A good illustration also of 

 this type of topography is Monument Mountain in Berkshire 

 county, whose main mass is composed essentially of a single 

 fairly uniform formation and is believed to owe its exceptionally 

 rugged topographic development almost solely to its joint and 

 fault planes. (See Fig. 8.) 



In the paper which has here been so frequently cited for 

 illustrations of fault structures the writer has used the expression 

 "floating block topography" in reference to a very striking 

 physiographic development, by which are revealed orographic 

 blocks, generally of similar size and shape standing at different 

 altitudes and with bounding fault-planes in evidence as scarps. 

 Fig. 1 1 displays such a type of physiographic relief. It is to 

 be noted that the blocks of this type (for convenience "unit" 



