XVI PREFACE. 



Some few suggestions that may appear in this 

 book might, perhaps, not be sanctioned by that 

 observer ; these, however, can be but few, as 

 most of the conclusions were discussed by us 

 together, and the constant result of our dis- 

 cussions was agreement. Any facts which are 

 stated without mention of any authority were 

 observed by one or other or both of us ; while 

 facts, the knowledge of which is due to other 

 observers, are given under their authority. 



This book is, in the first place, a record of 

 observed facts, but the conclusions we have 

 arrived at may be controverted by others ; how- 

 ever, we have tried to avoid putting forward 

 anything that is not in accordance with prece- 

 dent and ascertained operations of Nature. 



Plates Nos. I. and II. were drawn by the late 

 Mr Warren, while I am indebted to my colleague 

 Mr M 'Henry for Nos. III. and IV., and to Mr 

 Nolan for the characteristic sketch of the gravel 

 terraces in the Erriff river valley. 



G. HENRY KINAHAN. 



DUBLIN, March 1874. 



