VI PREFACE. 



lators, and the cause of so much unexpected delay in producing 

 this volume ; the more so as many of the subscribers to the 

 Scientific Library have expressed an interest in the subject, 

 owing, in some measure, to a controversy which arose out 

 of my previous publication of Cosmos. The translation was 

 originally entrusted to E. C. Otte, with an agreement as to 

 time, according to which I had every reason to expect that I 

 should fulfil my engagement to publish it in October last, or 

 at latest in November; but, after much of the manuscript was 

 prepared, the translator's indisposition and subsequent absence 

 from Loudon, occasioned a serious suspension. In this di- 

 lemma I found it necessary to call in aid, as well as to 

 assist personally. The result of this "co-operation of forces" 

 will no doubt prove satisfactory to the reader, inasmuch as 

 every sheet has been at least trebly revised, and it is hoped 

 projDortionably improved. In addition to the responsible 

 translator, my principal collaborateur has been Mr. R. H. 

 "Whitelocke, a gentleman well qualified for the task. 



All the measurements are calculated by the scientific friend, 

 who fulfilled this department so satisfactorily in my edition of 

 Cosmos. 



The translation of the pretty poem, The Parrot of Attires, 

 (page 189.) now first given in English, is contributed by 

 Mr. Edgar A. Bo wring. 



For the additional notes subscribed " Ed.'' I am myself, in 

 most instances, responsible. 



Much has been said, pro and con, about the sanction of the 

 Author to the several translations of his works. My answer 

 has, I believe, been generally considered satisfactory and 

 conclusive. I have now only to add, that when I wrote to 

 Baron Humboldt, more than a year and a-half ago, presenting 



