

PREFACE 



The Editor desires to acknowledge the assistance received from Mr. Buchanan, of the 

 Geological Survey Department, and from the officers of the Lithographic Department, in 

 the production of the plates. 



He also wishes to say that, in all but a few instances, a marked improvement has 

 taken place in the character of the manuscript, which has greatly facilitated the printing 

 of the work. 



