218 KEV. J. MILNE CURRAN. 



South Wales will show what an enormous extent of country is 

 overlain by the vast sheets of lava we term basalt, and my own 

 observations go to show that these rocks are even more extensively 

 developed than the latest maps indicate. We have a considerable 

 varietv too, both in the structure and the composition of these 

 lavas, ranging from the more basic basalts to the acidic trachytes. 

 The physical aspect of much of the Colony is due to the distribu- 

 tion of basalt, and quite recently I have noted that this rock is 

 the matrix of the sapphire found so widely over the New England 

 tablelands. Having made some notes on our basalts during the 

 past few years I venture to place before the Royal Society some 

 of the results obtained. 



In this first paper I propose to deal with a basalt from Bondi, 

 near Sydney, intrusive in the Hawkesbury Sandstone. There is 

 very little of the undecomposed rock visible, but the physical 

 effects of its intrusion and its proximity to Sydney are matters 

 of interest. 



Previous Observers. 



The first reference I find to a basalt near Sydney, is contained 

 in a paper by the late Rev. W. B. Clarke, on the "Transmutation 

 of rocks in Australasia," read to the Philosophical Society of New 

 South Wales, on the 10th of May, 1865.* Mr. Clarke refers to 

 the basalt as part of a dyke which he traced " from the mouth of 

 Lane Cove, through the Greenwich isthmus, on the other side, 

 and so into a dyke of similar character at Point Piper, and into 

 the sea, very near to the occurrence of the Meriveri columnar 

 sandstone and dyke of basalt a distance of six geographical miles."f 



There can be no question as to the identity of Meriveri with 

 the locality I refer to, that is the country around the north shore 

 of Bondi Bay. The name Meriveri has dropped out of usage, 

 and I will refer to the same rocks and place as Bondi sandstone 

 and basalt. Mr. Clarke deals with the basalt merely as the agent 



* Transactions of the Philosophical Society of New South Wales, 1862. 

 - 1865, page 294. 

 f Loc. cit., page 298. 



