the boundaries of the volcanic area can be determined by 

 a line limiting the occurrence of Eucalyptus salianaj the 

 commonest tree on the basic rock. 



Dundas. — The volcanic neck of Dundas is of much smaller 

 size than that of Hornsby but far more complex. It was 

 originally a hillock of columnar basalt outcropping through 

 Wianamatta shale;" but it has been quarried intermittently 

 for the past eighty years, and is now exposed in a quarry 

 about a hundred and sixty yards long, a hundred yards 

 , hundred feet deep. (See Fig. 2) Good 



wide, and 



beyond the excavation, the cultivation of the 



