Aet. XI. — The Sedimentary, Metamorphic, and Igneous 

 Rocks of Ensay. 



By A. W. Howitt, F.G.S. 



[Read November 12th, 1885.] 



Section I. — Introduction. 



In describing the rock formations of Swift's Creek and 

 Noyang, I have treated of the intrusive areas which border 

 the extensive tract of the metamorphic schists of Orneo. A 

 Swift's Creek the intrusion of the plutonic rocks was at the 

 very outside verge of the metamorphic schists, so that on one 

 side the invasive igneous masses were in contact with the 

 fine-grained mica schists of the Omeo series, and on the 

 other with Silurian sediments, which are in places converted 

 into varieties of hornfels. At Noyang the case is similar. 

 The quartz-mica diorites and porphyrites of that locality are 

 on their northern limits bounded by sedimentary rocks, 

 which show metamorphic alterations approaching to mica 

 schist ; on the southern boundary of the intrusive rocks there 

 are Silurian sediments converted into hornfels ; so that, 

 although the features are not so marked as at Swift's Creek, 

 this area is clearly one of those which, as I have elsewhere 

 pointed out, border the southern and eastern margin of the 

 so-called regional metamorphic schists of the Omeo district. 



In this paper I leave the tracts exterior to the metamor- 

 phic region, and enter upon the consideration of an area 

 within it, wherein occurs a series of peculiar rocks, which not 

 only differ from those which I have described as " contact 

 schists," but which are in some respects peculiar, even when 

 compared with the so-called " regional schists " of Omeo. 



There is to be seen at the junction of the Haunted Stream 

 with the Tambo River a part of the northern contact of the 

 quartz-mica diorite group with the Silurian sediments. I 

 have already elsewhere described this, and I now only refer 

 to it as a convenient starting-point for a new departure. 



In following up the Tambo River from its junction with the 

 Haunted Stream the valley contracts between high and 

 barren mountains, whose spurs interlock so much that it is 

 equally difficult to travel, whether on the mountain sides, 



