EDITOR'S PREFACE. 



THE subject to which this little volume relates is one of 

 deeper and more general interest than would be likely to 

 attach to a disquisition on any one branch of Natural 

 History, considered irrespectively of its relations to others. 



Whilst in an sesthetic point of view it recommends itself 

 to the attention of every traveller in a foreign country, and 

 indeed to all whose eyes are open to a perception of the 

 features of external .nature in their own, it connects itself, 

 at the same time, with many intricate questions concerning 

 the early history of our globe, the origin of organic beings 

 in general, the geological changes which our planet has 

 from time to time undergone, and the dependence of vege- 

 tation upon climate, altitude, and other external conditions. 



