Ordovician Rocks at Daylesford. 171 



strains, it may often happen that a crack which once tended 

 to open again tends to close, and a slate fragment may be thus 

 pinched off from the bed. Numerous cases were noticed of slate 

 fragments isolated in sandstone, but with a crack running to a 

 neighbouring slate bed, and to the place where such a bed might 

 have been. Some of these may not unlikely be wedges, but some 

 really isolated. 



This method of mixing of slate and sandstone may take place 

 wherever the cracking of the sandstone occurs, and the slate is 

 under pressure tending to squeeze it out. It may easily occur at 

 anticlines even, if only the packing of slate is sufficiently 

 complete. Its final stages may appear completely conglomei'atic 

 in section. 



These depend essentially on the fact that one material is more 

 plastic than the other, and are likely to be more marked the 

 greater the difference ; hence the occurrence of the most conglom- 

 eratic appearance with the coarsest sandstone. But in a case 

 like that at Italian Hill, when a slate is associated with a thin 

 coarse sandstone, and all is between thicker sandstones, the 

 mixed series will retain some plasticity even after the breaking 

 up has begun, as long as slate is fairly continuous, hence the 

 squeezing of the mass into the crack in the underlying sandstone. 

 Its squeezing out between the sandstones at its south end may 

 also be partly due to this. 



In a mixed slate and sandstone series between thicker sand- 

 stones, the sandstones may be cracked across, and the slate 

 squeezing into the cracks become continuous right across the 

 sandstone. This may be seen both at Leveret's cutting (107 to 

 107i miles), and at the big Wombat cutting (lOH to 102 miles) 

 Ballarat-Daylesford Railway. 



The direction of the longer axis of slate fragments in the sand- 

 stone is variable, the cracks which contribute to their formation 

 may or may not belong to some regular series of divisional planes. 



At Bald Hills Creek near the locality of Note 12, on Quarter- 

 sheet 16 N.E., occur slates with interlaminated hard sandy beds 

 to quarter-inch thick. These can be seen as regular parallel beds, 

 then becoming variable in thickness, then as nearly or quite dis- 

 connected lenticular patches, and at places the thin beds are bent 

 into sharp folds, and the sandy beds are often interrupted, 



