Ordovlcian Rocks at Daylesford. 17^ 



strata, both anticline and syncline might crush under their load 

 as arches, and produce radial surfaces of crushing, unless the 

 packing of the argillaceous beds were sufficiently rapid to prevent 

 it. 



In the straighter portions of the folds the direction of the 

 pressure might approximate to that of the general pressure; that 

 is, these surfaces might approach the cleavage direction, or it 

 might tend to be at right angles to the beds, in which case these 

 surfaces would approach tlie direction of stratification. 



The fact of actual movement on these surfaces in many cases 

 would then be the the result of yielding by slight slipping on 

 planes of weakness already established. Their curving to the 

 slate beds, as at Creswick, would probably be due to a yielding 

 by a viscous shear along these moi-e plastic beds. At Bald Hills 

 Creek both of these have very likely taken place, and this may 

 contribute to the abnormal strike 13" east of north, though 

 further north, at a short distance, where this structure had 

 disappeared, a normal strike N. 11° W. had been resumed. 



The series of phenomena described all seem to indicate that in 

 examining the effects of folding on a mixed series of rocks of 

 different character due attention must be given to the differ- 

 ences of rigidity and probably compressibility of the different 

 beds, and their manner of yielding under the strains to which 

 they have been subjected. 



