Geolof/tj of Broadnieaduivs. 159 



the Camel's Hump. More to the west lies Mt. Blackwood, and 

 the Werribee Gortre may also be seen. To the south-west rises 

 Mt. Cotterill amongst other volcanic cones, and further on the 

 bold outstanding granite peaks of the You Yangs. 



Tlie granite hill is part of a more or less circular outcrop of 

 granite which has been cut in two by a north and south lava 

 stream, and is the nearest outcrop of a granite massif to Mel- 

 bourne, apart from granitic dykes in Melbourne itself. This 

 was no doubt one of the factors bearing on its use as a building 

 stone for the old Princes Bridge, Chief Secretary's Office, and 

 Town Hall. 



As to its geological relations, along the southern margin it is 

 represented on the map as being in contact with the sihirian, 

 but the exposures are very poor. In a small creek in Section 

 Vin. Will Will Rook, which runs down from the granite hill, 

 the Silurian sandstone and granite can be found in situ within 

 a short distance of one another. The sandstone preserves the 

 general strike, and shoAvs no alteration, but on examination is 

 found to contain pockets of shale. In Section IX., in the first 

 exposure of silurian rocks met with in following down the bed of 

 the creek, the general strike is not so Avell preserved. The 

 shale bands here show evidence of squeezing, and contain nodular 

 concretions of harder rock. One of these nodules was sectioned. 

 From another shale band which appeared to be very indurated 

 another specimen was taken and sectioned. Both these sections 

 approached the hornfels type. A specimen was also obtained 

 from a loose boulder along the approximate boundary in Sec- 

 tion YII. TTiis, when sectioned, was also found to be a hornfels. 



The evidence (though small in quantity) is therefore distinct 

 as to the slight metamorphism of the silurian sediments by the 

 intrusion of the granite. The granite is therefore post silurian, 

 and correlating with the Yictorian grano-diorites, as we are 

 justified in doing by its chemical and petrological characters, 

 we may consider it as devonian in age. 



Kaolinised Granite. 



Along the creek in Section IX., Will Will Rook, is to be found 

 a white face of kaolinised granite, exposed in a small gully about 



