Geology of Mount Macedon. 189 



Brock's Monument is named Alexander's Head on Skene's^ 

 Map of Victoria and the Index map of the Geological Survey, 



III. — Geological Literature on Macedon. 



The list of geological literature on Mount Macedon is brief. 

 The first reference is that of Mitchell, according to whom the 

 mountain is formed of " syenite so whitened with the weather as 

 to resemble sandstone."^ 



The next important contribution to the geology of the moun- 

 tain is the map prepared by C. d'O. Aplin under the direction of 

 Dr. A. R. C. Selwyn (1). This map, which is on the scale of two 

 inches to the mile, shows the boundaries of the Macedon igneous 

 rocks, but gives little information as to their relations and 

 variations. The whole series is represented by one colour, and 

 is described as " trap or hypogene " ; a note on the Camel's 

 Hump states that the rock there is a porphyritic felspar trap, 

 while the rock of the south-western shoulder (the Mount 

 Macedon of the map) is said to be a non-porphyritic felspar trap. 

 The only interruption in the area of the " traps " is the occur- 

 rence of a granite dyke on the western flank of the mountain. 



After the publication of the Geological Survey Map, brief 

 descriptions of some of the Macedon rocks were given in 

 Selwyn's Catalogue (No. 19, pp. 12, 13, 65, 94, 95). The rocks 

 of the Camel's Hump, the Hanging Rock, Brock's Monument, 

 and the eastern flank of Macedon were all classed as plutonic 

 rocks and were named "felspar porphyry." The most important 

 information about the Macedon rocks given in this Catalogue is 

 an analysis of the " Camel's Hump " rock, which is returned as 

 having the high soda percentage of 10-17. The interest of this 

 determination was, however, apparently overlooked. 



In 1894 there was a proposal partially to adopt Mitchell's 

 original name for the Macedon rock ; for Cosmo Newbery, in his 

 " Descriptive Catalogue of Victorian Rocks" (15, p. 26), described 

 Brock's Monument as composed of syenite porphyry containing 

 hornblende and very glassy looking orthoclase. 



1 Everett's Edition of Skene's 8 miles to the inch Map. Surv. Geol. Vict. 



2 The determination of the rock as syenite is due to Lonsdale. Cat. Aust. Rocks in Coll. 

 Geol. Soc, Pari. Pap., Gt. Brit., 1852-3, vol xvi., p. 433. Lonsdale also determined the 

 rock at the base of the north side of the mountain as a "decomposed gneiss." 



