528 J. T. Jntson: 



yet much slipping does not appear to have taken place. This 

 is shown by the i*epetition of the grits and conglomerates at 

 Warrandyte, which from the general appearance of their fossil 

 contents, and their lithology indicate their connection with one 

 another. A possible line of faulting is the main dyke east of 

 the Caledonia mine, which has been traced several miles, bu^. 

 for the reasons given when treating of the cause of the hori- 

 zontal limitation of the Warrandyte field, this is probably a 

 fracture with little displacement. The general structure of the 

 country as above indicated, suggests that no important move- 

 ment has taken place along this line. 



An important fault, but belonging to a much later period 

 than the folds and fractures of the silurian rocks generally, is 

 marked on the map as the Brushy Creek Fault. This is fully 

 dealt with in the paper on the physiography of the Yarra 

 River and Dandenong Creek Basins, and need not be further 

 discussed here. 



Dykes. — The principal one is that noticed under the pi^eced- 

 ing section ; a little to the east is another one. They are indi- 

 cated on the accompanying maps so far as traced by the writer, 

 but one, accoi'ding to Mr. ^Miitelaw's geological map of part 

 of the Nillumbik Parish, runs as far as Kangaroo Ground. They 

 are about 8 or 10 feet wide and dip to the east, the more 

 westerly one at 60 deg. and the other at about 45 deg. The 

 rock is so decomposed that it cannot be determined. The dykes 

 contain thin auriferous quartz veins. Other dykes are marked 

 on Mr. Moon's Quarter Sheet, and others occur near Croydon, 

 where they have been worked for kaolin. 



Mr. A. M. Howitt (11, p. -±0) discovered when at Warrandyte 

 a basic dyke about 2 feet in width in the Caledonia Mine cut- 

 ting across a cross-course. The rock was fairly fresh, and en- 

 abled Prof. Skeats to determine it as a monchiquite. 



Joints. — These in general call for no special remarks. In 

 most cases they do not pass continuously through different rock 

 beds. Dip and strike joints are sometimes fairly well developed, 

 and in thick-bedded homogeneous shaly rocks cause great diffi- 

 culty in determining the dip. Some jx)ints of interest in con- 

 nection with joints may be noted. 



