8 
Preface to the Second Edition 
district, very kindly placed liis work at my disposal. 
The geological map now added to this volume is 
therefore the joint work of Mr. Ball, Mr. Rienits, and 
the present writer. The district coloured was selected 
as being an area easily accessible to the student, and 
one in which the rocks vary considerably in age and 
character. The map facing the title page shows the 
position of a number of igneous dykes around Sydney 
of which no record has hitherto been published. 
Some friendly critics have found fault with the 
disposition of the illustrations, pointing out that the 
figures are not always on the same page as the text 
referring to them. Geological pictures of general 
interest, illustrating many principles may, I think, 
be distributed with their explanatory legend , through 
a volume such as this. 
I would express my indebtedness to Professor 
David, of the University, for reading through the 
book, making some corrections, and giving me many 
valuable suggestions which are embodied in this 
edition. For information and assistance generally I 
have to thank Mr. John Mitchell, Mr. David Wiley, 
Mr. J. M. Taylor, LL.B., Mr. A. G. Hamilton, and Mr. 
W. J. Enright. 
J. M. C. 
