AUTHOR'S PREFACE. xl 



no inconsiderable difficulties in the choice of the form under 

 which such a work must be presented, if it would aspire to 

 the honour of being regarded as a literary composition. 

 Descriptions of nature ought not to be deficient in a tone of 

 life-like truthfulness, whilst the mere enumeration of a series 

 of general results is productive of a no less wearying impres- 

 sion than the elaborate accumulation of the individual 

 data of observation. I scarcely venture to hope that I have 

 succeeded in satisfying these various requirements of compo- 

 sition, or that I have myself avoided the shoals and breakers 

 which I have known how to indicate to others. My faint 

 hope of success rests upon the special indulgence which the 

 German public have bestowed upon a small work bearing the 

 title of Ansichten der Natur, which I published soon after my 

 return from Mexico. This work treats, under general points 

 of view, of separate branches of physical geography, (such as 

 the forms of vegetation, grassy plains, and deserts.) The 

 effect produced by this small volume has doubtlessly been 

 more powerfully manifested in the influence it has exercised 

 on the sensitive minds of the young, whose imaginative facul- 

 ties are so strongly manifested, than by means of anything 

 which it could itself impart. In the work on the Cosmos on 

 which I am now engaged, I have endeavoured to show, as in 

 that intitled Ansichten der Natur, that a certain degree of 

 scientific completeness in the treatment of individual facts, is 

 not wholly incompatible with a picturesque animation of 

 style. 



Since public lectures seemed to me to present an easy and 

 efficient means of testing the more or less successful manner of 

 connecting together the detached branches of any one science, 

 I undertook, for many months consecutively, first in the French 

 language, at Paris, and afterwards in my own native German, 

 at Berlin, (almost simultaneously at two different places 

 of assembly,) to deliver a course of lectures on the physical 

 description of the universe, according to my conception. 



