viii PKF.FACR. 



affords the means of testing and sometimes of cor- 

 recting such statements. In a work like the present, 

 where explanation and description take the place of 

 reasoning, there is no such check. For this reason I 

 have been very careful in the accounts which I have 

 given of the subjects here dealt with. I have been 

 particularly careful not to present, as established 

 truths, such views as are at present only matters 

 of opinion. 



The essays in the present volume are taken chiefly 

 from the Contemporary Review, the Gentleman's Maga- 

 zine, the Cornhill Magazine, Belgravia, and Chambers' 

 Journal. The sixth, however, presents the substance 

 (and official report) of a lecture which I delivered 

 at the Royal Institution in May, 1870. It was then 

 that I first publicly enunciated the views respecting 

 the stellar universe which I afterwards more fully 

 stated in my " Universe of Stars." The same views 

 have also been submitted to the Paris Academy of 

 Science, as the results of his own investigations, by 

 M. Flammarion, in words which read almost like 

 translations of passages in the above-mentioned 

 essay. 



RICHARD A. PROCTOR. 



