AUTHOR'S PREFACE 



TO THE 



SECOND AND THIRD EDITIONS. 



THE twofold aim of the present work (a carefully prepared 

 and executed attempt to enhance the enjoyment of Nature by 

 animated description, and at the same time to increase in 

 proportion to the state of knowledge at the time the reader's 

 insight into the harmonious and concurrent action of different 

 powers and forces of Nature) was pointed out by me nearly 

 half a century ago in the Preface to the First Edition. In 

 so doing, I alluded to the various obstacles which oppose a 

 successful treatment of the subject in the manner designed. 

 The combination of a literary and of a purely scientific 

 object, the endeavour at once to interest and occupy the 

 imagination, and to enrich the mind with new ideas by the 

 augmentation of knowledge, renders the due arrangement 

 of the separate parts, and the desired unity of composition, 

 difficult of attainment. Yet, notwithstanding these dis- 



