Geology of Mount Macedon. 205 



gation. The Macedon solvsbergites, though resembling those of 

 Southern Norway, have not been derived from the same magma. 

 The Kristiania solvsbergites have been formed by differentiation 

 from laurdalite, a plutonic rock composed of anorthoclase, crypt- 

 operthite, elaeolite, lepidomelane, and a monoclinic pyroxene. 

 In spite of the very varied series of rocks that has been developed 

 from the laurdalit magma, it does not include any equivalent of 

 the soda-hypersthene-dacite, which is the lowest exposed rock at 

 Macedon. 



A second series of allied rocks occurs in Abyssinia. The rocks 

 have been described in a valuable paper by Mr. E. T. Prior; but 

 these rocks are said to be a dyke series, and there is no close ally 

 of the geburite-dacites. 



VII. — The Geological Structure of Mount Macedon. 



The dense forest growth that covers Mount Macedon obscures 

 the mutual relations of its rocks. Nevertheless, by piecing 

 together the evidence of many parts of the area the general 

 arrangement can be determined. 



The best idea of the structure of Mount Macedon can be 

 obtained by a traverse north and south across the ridge from the 

 township of Macedon on the south over the Camel's Hump and 

 thence through Hanging Rock to the village of Newham on the 

 north. 



In such a traverse we find the first exposures of igneous rocks 

 on the northern side of a branch of the Saltwater River and to 

 the north-east of Macedon cemetery. Here the geburite-dacites 

 rest on the Ordovicians. The igneous rocks are exposed in a 

 small quarry, in occasional hummocks in the forest, and in the 

 bed of the Turritable and Willimigongong Creeks. The dacites 

 have a well-developed fluxion structure where they rest on tlie 

 Ordovicians ; but in the main mass of the eruptive rock the 

 structure is holocyrstalline and granulitic. On the lower slopes 

 of this part of Macedon there are dykes of trachy-phonolite and 

 geburite-dacites ; but the field relations of these dykes are not 

 clearly shown. Continuing the ascent towards the main ridge 

 we pass over some agglomerate and ash traversed by dykes, and 

 then over thick effusive masses, as well as some apparently 



