xii author's preface. 



by the improvement in the instruments used, and by the coin 

 sequent expansion of the field of view opened to rational ob • 

 servation, and that those scientific works which have, to use 

 a common expression, become antiquated by the acquisition 

 of new funds of knowledge, are thus continually being con- 

 signed to oblivion as unreadable. However discouraging such 

 a prospect must be, no one who is animated by a genuine love 

 of nature, and by a sense of the dignity attached to its study, 

 can view with regret any thing which promises future addi- 

 tions and a greater degree of perfection to general knowledge. 

 Many important branches of knowledge have been based upon 

 a solid foundation which will not easily be shaken, both as re- 

 gards the phenomena in the regions of space and on the earth ; 

 while there are other portions of science in v/hich general 

 views will undoubtedly take the place of merely special : 

 where new forces will be discovered and new substances will 

 be made known, and where those which are now considered 

 as simple will be decomposed. I would, therefore, venture to 

 hope that an attempt to delineate nature in all its vivid ani- 

 mation and exalted grandeur, and to trace the stable amid the 

 vacillating, ever-recurring alternation of physical metamorph- 

 oses, will not be wholly disregarded even at a future age. 

 Pottdam, Nov., 1844. 



