08 



Fig. 2. — Sketch Map of the country about Adelaide, showing, 

 localities mentioned in this paper and area geologically mapped. 



of these porphyroblasts may be noted. A good example of 

 this is to be found in the creek which flows from the Lady 

 Alice Mine down past the Humbug Scrub Post Office. Micro- 

 scopical examination shows the essential similarity of these 

 rocks with the schists of Houghton. They are more highly 

 metamorphosed, and the felspar is perhaps derived from plu- 

 tonic solutions, but the augen structure is here a metamorphic 

 structure. The rocks are not crushed granite-porphyries. 



Aldr/afe. — The occurrence in this area has been described 

 at some length by Mr. Howchin.^5) Schists of a nature simi- 

 lar to those of Houghton are intru.ded by plutonic rocks 

 closely similar to those which occur at the latter locality. 

 These rocks are exposed typically at the corner of the main 

 Adelaide road about 200 yards from Aldgate Railway Sta- 

 tion ; they are here very fine in grain. On the hillside to the 

 north they are coarser, but then disappear beneath Cambrian 

 rocks, reappearing in Sections 1118 and 1133 of the Hundred 



^9) Op. cit. sup., p. 251. 



