2 Definition of Geology. 



organic and organic kingdoms of nature, together with 

 the causes of these changes, as far as they can be traced 

 by observations on the structure and mode of occurrence 

 of the mineral and organic bodies that form or are 

 found in and upon the crust of the earth. 



To place the events of this complicated history in 

 clear chronological succession is the chief business of 

 the geologist; and in doing so he unites the present 

 with past geological epochs, and discovers that the 

 physical world, as it now exists, is the result of all the 

 past changes that have taken place in it. If, therefore, 

 our knowledge were sufficient to admit of the construc- 

 tion of a complete system of physical geography, it 

 would be but a full description of a geological epoch 

 namely, that of to-day ; and a complete account of any 

 old geological epoch, would be a perfect description of 

 the physical geography of the world at that time. 



To us, the chief dwellers on the Earth, the whole 

 subject is of the greatest interest, and it is therefore 

 my intention to endeavour to show in a simple manner 

 taking our own island as an example whence the 

 materials that form the present surface of the earth 

 have been derived, why one part of a country consists 

 of rugged mountains, and another part of high table- 

 lands or of low plains ; why the rivers run in their pre- 

 sent channels ; how the lakes that diversify the surface 

 first came into being. In the course of this inquiry I 

 shall have occasion to show that Britain has been joined 

 to and severed again and again from the continent, 

 and how some of the animals that inhabited, or still 

 inhabit it, including its human races, came to occupy 

 the areas where they live. 



Assuming that I am partly addressing those who 

 have not previously studied geological subjects in detail, 



