The VOLCANIC NECKS of HORNSBY ani 

 NEAR SYDNEY. 

 By W. N. Benson, b.sc. 



[With Plate XXXIV.] 

 {Read before the Royal Society of N. S. Wales, November 

 Part I. General. 



Introduction. Field Geology Hornsby. Dun 

 Part II. Penological. 



Dundas : Minerals of the Plutonic Inclusions. 

 Classification of the Plutonic Incluaior 

 Structures of the Plutonic Inclusions. 

 Types of the Plutonic Inclusions. 

 Inclusions other than Plutonic. 

 The Breccia. 

 The Basalt. 



Interactions between the Basalt and th 

 Hornsby: The Breccia. The Inclusions. 

 Part III. Mineralogical Notes. 



ledgements. 



Part I. Geneal. 

 Introduction.— The volcanic necks at Hornsby and Dun- 

 das have been known to geologists for a considerable time, 

 and the latter has been frequently mentioned in literature. 

 The earliest record of Dundas is that by J. D. Dana. 1 It is 

 also mentioned by the Rev. W. B. Clarke 2 and was reported 

 upon by O. S. Wilkinson. 3 The last named recorded the 

 occurrence of numerous inclusions of foreign rock in the 



1 Report of U. S. Exploring Expedition, 1838-42, Vol. x. 



* Transmutation of Kocks in Australasia. Trans. Phil. Soc. N.S.Wales 

 \**2- IMJS, p. 292, 



* Ann. Eep. Department of Mines, N.S.W T ., 1876. 



