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Mr. President and Fellow-Members of the American 

 Philosophical Society : — In the part which you have 

 assigned to me in this Centennial Commemoration, I find my- 

 self called upon to deal with a subject the compass of which 

 is wholly beyond my powers ; as it is all too ample for the 

 limited time available. In the eloquent address in which 

 you, Mr, President, retraced the history of this, the oldest 

 among the scientific societies of America, you found an hour 

 too brief for a review of the events of the cen+ury which 

 to-day completes itscj^cle; and now I find myself called upon, 

 in the briefer limits at my disposal, to verify the entire Book 

 of Nature, and demonstrate the faultless perfection of the 

 record. Looking back over the immeasurable ages of the 

 past, and turning to the equally incomprehendable vastness 

 of the visible universe, hours, instead of minutes, would fail, 

 in the most superficial efibrt at such a review. 



Amid the brightness of this festive commemoration, the 

 temptation is rather to leave the past unheeded, and to take 

 the wings of fancy — or, better still, the intuitions of science, — 

 and anticipate the marvels of the coming time ; those fairy tales 

 of science that surpass all the wonders of romance. But your 

 behest must be obeyed ; and it will perhaps most aptly meet 

 present requirements if I select from the manifold phases 

 which challenge our consideration two suggestive aspects of 

 the comprehensive subject, which in some sense may serve to 

 epitomize the past and the present for such brief review. 



When the fiat went forth, formulated in words that might 

 fitly constitute the motto of this, the oldest among the philo- 

 sophical fellowships of the New World: "Let there be light!" 

 the abyss flashed into cosmic brightness and beauty ; and the 

 illimitable depths of space, illumined with the splendor that 

 enkindled suns, and awoke the myriad worlds to life, traced for 



