BY W. N. BENSON. 571 



of material, would occasion some oscillatory movement in the 

 water on the sea-floor, which might result in a sedimentary struc- 

 ture resembling current-bedding in the mass of the silt lifted 

 and redeposited at each convulsion. The specimens illustrated 

 by Text-figs. 8 and 9 may perhaps be an example of this. We 

 may compare with figure 8, the illustration of false bedding in 

 chert seen by Clements in the Pre-Cambrian rocks of Michigan, 

 which are also associated with tuflfs (22, Plate xxvii.). It 

 must be noted, however, that ripple-markings were seen among 

 these rocks by the previous authorsO). According to Hunt(23), 

 these do not necessarily indicate a very shallow sea. They may 

 form at considerable depths, as much as 188 metres in one 

 instance cited, It is not clear to the writer whether the features 

 seen in Text-fig. 8 are the result of a general rippling oscillation 

 or eddying produced as suggested above. The extremely local 

 character of the phenomena may indicate that the latter alterna- 

 tive is the more probable. 



Intrusions Of pyroclastic rock into more consolidated chert 

 would require more energetic explosions than those described 

 above, and would result in much shattering. Rocks which 

 illustrate this are very frequent along the west side of the 

 serpentine in Spring Gully, and have been found in the Nundle 

 District(17, pp. 166-7.* See also p. 575). 



The conception here advanced, of the semi-liquid nature of 

 unconsolidated fine-grained sediments, is in accord with the 

 results of Dr. Sorby's studies(34). Injection of pyroclastic 

 material into sediments with varying degrees of consolidation 

 down to that of a "creamy" {op. cit., p. 197) consistency, would 

 naturally result in an appropriate variety of intrusion-phenomena. 

 Ejection into the open water, and normal sedimentation would 

 be the limiting case. 



Another igneous complex of great interest occurs in Mr. 

 Macllveen's property (Portions 180, 175, and 162, Parish of 

 Nemingha), about two miles south of East Gap Hill. A sketch- 



* In the first part of this series of papers(i4), a diff"erent explanation of 

 the intrusive tuflfs was suggested, but experience has shown it to be un- 

 tenable, and it has been withdrawn(i7, loc. cit.). 



