258 F. H. Laliee — Metamorjphism and Geological Structure. 



Almost without exception, however, the axes of the major folds 

 trend a little east of north, thus proving that the maximum 

 deforming forces acted along approximately east-west lines. 



Relative number of folds across the Basin. — East-west sec- 

 tions across the Basin show a varying number of folds in differ- 

 ent latitudes. To illustrate this fact, sections along lines A- A, 

 B-B, and C-C (fig. 1) have been drawn, as nearly" as possible 

 perpendicular to the strike (see figs. 5 to 7). By dividing the 

 number of major folds (both anticlines and synclines) inter- 



Figs. 5, 6, 7. 



w 



, „ — T= 



=**==- 



„--. <Q^--- 



Scale in miles. 



Fig. 5. Generalized vertical section along the line A-A in fig. 1. 

 Fig. 6. Generalized vertical section along the line B-B in fig. 1. 

 Fig. 7. Generalized vertical section along the line C-C in fig. 1. 



sected by any line by the length of this line, we may estimate 

 the number of fold's per unit of length of the given line, that 

 is, per unit of width of the Basin where the line is situated. 

 In each case land and water areas are traversed. Since the 

 determination of the folding is founded upon data obtained on 

 land, we have calculated the results not only upon the total 

 lengths of the lines, but also upon the sums of their land 

 portions. An important source of error lies in the method of 

 interpreting the geological structure, and the opportunity for 

 mistake is greater in the north than in the south. To offset 

 such error we have chosen, in each case, that interpretation 

 which assumes the greatest reasonable number of folds. For 

 example, in the Cranston area, where the structure has been 

 explained by some as monoclinal and by others as consisting of 



