SOME EXPERIMENTS IN FOLDING 



503 



Cavities between the layers of the anticlines and the synclines 

 were most common where the folding was least intense (Fig. 6). 

 It is not certain, however, that this principle can be applied to the 

 location of such ore deposits as the saddle reefs of Bendigo, for there 

 the access of solutions and other factors doubtless play an important 

 part. Pockets of oil and gas should be more abundant where the 

 folding is very gentle. 



Competent layers between incompetent. — Experiments were per- 

 formed in which fairly competent brittle layers were inserted 

 between very plastic layers. The former were made with 4 parts of 



Fig. 9. — Original length 25 inches; compressed 8 inches. Layers i, 4 and 6 were 

 I paraffin, 12 vaseline. Layers 2, 3 and 5 were i par., i vas. Layers 2 and 3 appear as 

 one. Softer layers much distorted. Strangle folds developed. 



paraflEin to 3 of vaseline, and the latter with 3 parts of vaseline to i 

 part of paraffin. It was found that after compression had shortened 

 the models by a few inches, the competent layers folded without much 

 internal distortion, but that the plastic layers were tremendously 

 distorted, being thickened on the crests of the anticlines and in the 

 troughs of the synclines, with much stretching on the limbs (Figs. 

 9 and 10). In the early stages of folding there was a general corre- 

 spondence between the anticlines and synclines in the layers of 

 different competency, but, with further compression, the brittle 

 layers developed minor folds which were entirely at variance with 

 the surfaces of the plastic material. This was possible because of 

 the great thickening of the plastic layers whose ready yielding greatly 



