186 Proceedings of the Royal Society of Victoria. 



rises abruptly from the broad basalt plains at its foot ; and its 

 outline stands boldly on the skyline above tlie level plains and 

 dissected plateaux, which combine with it to form the northern 

 and western rim of the great Melbourne basin. 



The interest of the appearance of Mount Macedon is heightened 

 to a geologist by the uncertainty as to its age and structure 

 expressed on the maps of the Geological Survey of Victoria. 

 The rocks are described as "Trap or Hypogene," and in the 

 official geological handbook to the State, its age is suggested 

 as probably late Palaeozoic, though on admittedly inadequate 

 grounds. 



This uncertainty is unfortunate, for a short acquaintance with 

 the geology of the Melbourne area shows that Macedon is one of 

 a series of similar igneous blocks, whose age and stratigraphical 

 relations must be determined before the volcanic history of 

 Victoria can be satisfactorily written. 



In my first visit to Mount Macedon I had the privilege of the 

 guidance and company of Mr. H. R. Hogg and Professor 

 Spencer. I have also to express my thanks for much assistance 

 in a subsequent visit to Mr. H. J. Grayson, who has prepared the 

 photographs of the rock sections, as well as the sections them- 

 selves. I am indebted to Professor Orme Masson and Mr. R. J> 

 Lewis for analyses of two Macedon Rocks ; to Mr. H. C. Jenkins, 

 A.R.S.M., for the analyses of allied rocks from the Dandenongs 

 and Blacks' Spur; and to Mr. A. Everett for some advice as to 

 the geographical nomenclature. Mr. E. T. Prior, of the Minera- 

 logical Department of the British Museum, has very kindly 

 examined some rock sections and given me the benefit of his 

 opinion on some doubtful points, which is of especial value owing 

 to his careful study of the allied rocks of Abyssinia. 



II. — The Geographical Features. 



Mount Macedon was discovered by Hume and Hovell in 

 1824. They saw it from Mount Disappointment, and named it 

 Wentworth, after the distinguished champion of Australian 

 liberty. The mountain was, however, fii'st visited by Sir 

 Thomas ^Mitchell, during his memorable journey from Sydney 

 through Australia Felix. He ascended the mountain on 30th 



