and their Contact Zones. 



69 



the surface of the igneous rocks. Their directions of dip and 

 strike are not only not in accord with the surface of the 

 igneous rocks, but in the immediate contact the sediments 

 are broken, crumpled, and cut off. These appearances of 

 intrusion are most distinctly manifested when the contact 

 crosses the direction of the strike of the sediments ; while, 

 on the other hand, the sedimentary beds when the direction 

 of the contact and their strike coincide, are found to inter- 

 lock in their most altered condition with the marginal rock 

 masses of their intrusive neighbours. Such a contact may 

 be imagined as I have roughly sketched it, and in its fea- 



Diagram No. 4. — Representing the Contact. 



tures it agrees with the observations which I have made 

 ■as to similar contacts in other parts of Victoria. These 

 ■appearances suggest most strongly to me, not only the 

 intrusion of the plastic igneous rocks, but also as strongly 

 the absorption, so long as the conditions remained the same, 

 of portions of the invaded sediments ; and further, that these 

 processes must have been intermittent and of long duration. 

 This contact zone is, as seen at the surface, of varying width. 

 We should expect it to be so when we consider that the 

 contact surface itself must be highly irregular, so that it 

 must in places be far nearer to the present surface than else- 

 where, or extend beneath it at varying angles with the 

 horizon. From various approximate measurements, I believe 

 the width of the zone from the main intrusive mass to 

 those schists which are least altered, and wherein commences 



