AUTHOR'S PREFACE. 



[N the late evening of an active life I offei to the German 

 public a work, whose undefined image has floated before my 

 mind for almost half a century. I have frequently looked upon 

 its completion as impracticable, but as often as I have been 

 disposed to relinquish the undertaking, I have again although 

 perhaps imprudently resumed the task. This work I now 

 present to my co temporaries, with a diffidence inspired by a 

 just mistrust of my own powers, whilst I would willingly for- 

 get that writings long expected are usually received with less 

 indulgence. 



Although the outward relations of life, and an irresistible 

 impulse towards knowledge of various kinds, have led me to 

 occupy myself for many years and apparently exclusively 

 with separate branches of science, as, for instance, with 

 descriptive botany, geognosy, chemistry, astronomical deter- 

 minations of position, and terrestrial magnetism, in order that 

 I might the better prepare myself for the extensive travels in 

 which I was desirous of engaging, the actual object of my 

 studies has nevertheless been of a higher character. The 

 principal impulse by which I was directed, was the earnest 

 endeavour to comprehend the phenomena of physical objects in 

 their general connection, and to represent nature as one great 

 whole, moved and animated by internal forces. My inter- 

 course with highly gifted men early led me to discover that 

 without an earnest striving to attain to a knowledge of special 

 branches of study, all attempts to give a grand and general 

 virw of the universe would be nothing more than a vain 

 illusion. Theoe special departments in the great domain of 



