44 FIELD GEOLOGY. 



Note. These rules will not apply, unaltered, to 

 lines of apparent dip, enclosing acute angles which 

 in practice are rarely found, but to right angles and 

 all beyond they are applicable. In such cases, a 

 horizontal triangle constructed by the reverse rule, 

 i.e., on the opposite side of either line of observed 

 dip, will give the result required. (See the N.E.. 

 corner of quarry, fig. 14, as an illustration.) 



Fig. 13. 



From the preceding two rules a general one may be 

 drawn, and which as an aid to memory of the others 

 may be of service. When the apparent dips cross each 

 other, as in a (fig. 13), the dip crosses the line which 

 will be drawn by Eule A. When all run in the same- 

 direction, 6, the dip coincides with the line drawn by 

 Eule B. 



Note. When any part of the section-face shows 

 the beds in a horizontal position, the true dip (if 

 any) is of course at right angles thereto, and no> 

 further trouble need be taken. 



The quarry represented in fig. 14 may be taken as an 

 example of obtaining the true dip by these method s, 

 the operation being repeated, and in each case with the 

 same result. 



