Older Basalts of Greenshoroitgk, etc. 63 



On the other hautl. tlie Mount has been well dissected on most 

 sides, and the basalt appears to be lying on the quartziie. If a 

 plug exist, it occurrence has not yet been actually demonstrated. 

 Again the. basalt on the top of the quartzite. when examined in situ, 

 if. dense and non-vesicular, in this respect in hand specimens, 

 resembling more the (ireensborough Older Basalt than the typical 

 Newer Basalt. It also occurs at such a height that if erosion had 

 proceeded so far as to remove all traces of basalt on the nortli- 

 eastern slope, the high basalt would certainly have been regarded 

 merely as another outlier of such Older Basalt of Greensborough. 

 It is for these reasons that the writer ventures to doubt tlu; correct- 

 ness of the Survey interpretation. 



In the absence of a sufficient examination of the urea since this 

 doubt arose, a definite opinion on the point cannot be (jffered, but 

 as a hint to anyone taking up the investigation, attention should 

 be paid to the low hill to the east, which may be the remains of au 

 old vent of the Newer Basalt period. If so, the occurrence of such 

 basalt above its general level might be explained, and at the same 

 time make it possible for the basalt on the top of Mt. Cooper to be 

 another outlier of the Older Basalt of Greenslxirough or perhaps the 

 plug of an old vent of such Older Basalt, l)ut there is little more 

 (if any) ground for the latter alternative than for any of the basalt 

 caps of the Greensborough area. 



Microscopical examination might thiow .some light on the ques- 

 tion, and the small patches of Newer Basalt on the eastern side of 

 the main road at Bundoora (which the writer has not seen) should 

 iiho be studied. 



The Ivanhoe High-Level Basalt. 



On several occasions some yeiirs ago, the writer endeavoured 

 to locate the " basalt boulders " marked on the Quarter-Sheet. Tlie 

 " siliceous conglomerate " was easily fixed by an outcrop on the 

 roadside, but no trace of the basalt could be found, and the matter 

 'was dismissed as a mistake of the field geologist or draftsman. Some 

 time later, however, on happening to pass that way again, several 

 holes up to about 4 ft. deep were being dug in connection with the 

 formation of a nursery, and in these holes the " basalt boulders " 

 revealed themselves, thus offering another testimony to the remark- 

 able accuracy of the early Victorian Geological Survey. The basalt 

 was close to the siliceous conglomerate, and apparently only a few 

 yards in extent. 



The "basalt boulders" consisted of rounded, semi-rounded and 

 angular blocks, having on the average a diameter of about 10 inches 



