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external world, cannot aspire to completeness ; the nature 

 of tilings, and the imperfection of our organs of sense, 

 are alike opposed to it. No mortal has heen permitted 

 to penetrate all the arcana of the physical universe and 

 comprehend the ' whole ; but as science advances the 

 insight must become more extensive, and even a partial 

 solution of the problem will always remain the eternal 

 and sublime aim of every investigation of Nature. Vanity 

 or self-complacency may lead some minds to believe that, 

 in their own age, humanity has reached the culminating 

 point of intellectual progress ; but such a view is at vari- 

 ance alike with history and the laws of thought. The 

 internal connection existing among all phenomena, ren- 

 ders it certain, that every discovery in science prepares 

 the way for higher conquests, and forces upon us the 

 conviction, that when thousands and thousands of years 

 have passed, untrodden paths will still be opened to the 

 scientific observer, leading him to an illimitable world of 

 thought. The regret of Alexander cannot be applied to 

 the progress of observation and intelligence ; for there is 

 no quiet resting place, no pause, except in the invariable, 

 eternal, all-comprehensive source of order, and harmony^ 

 and beauty. 



The finite nature of our faculties and the position we 

 hold in the physical world, combine to render it impos- 

 sible for man to embrace the whole of Nature in its 

 universality. Physical causes have entirely concealed 

 three^evenths of the surface of our satellite from our obser- 

 vation, and this must always remain so, under existing 

 cosmical arrangements. The zone of a few degrees in 

 breadth on all sides of the border beyond an exact hemi- 

 sphere, which is brought into view by her librations, only 



