102 THE PRESIDENTS ADDRESS. 
analysis. What a wonderful example is presented, in this most beau- 
tiful and valuable discovery, of the progress of human knowledge! 
About two hundred years ago Sir Isaac Newton astonished the 
scientific world by the discovery of the composition of solar light, and 
for many years it was a favorite optical experiment to produce the 
spectrum by a prism, and prove the variety of the tints that are 
cowbined in what had been regarded as simply white light. Just 
sixty years have elapsed since Wollaston added to our knowledge of 
the spectrum by the discovery of the seven dark lines. The subject 
thus commenced in England was taken up by Fraunhofer who observed 
no less than 590 of these lines, and since his time the number has 
been increased by the researches of Brewster and Gladstone to about 
2000. In Kirchoff’s experiments five prisms were used, and he has 
succeeded in producing an exact map giving the distances, the breadth, 
and the degree of darkness in the lines. But this is not all. With a 
similar instrument he and Professor Bunsen examined the spectra of 
the chemical elements, and the application of this new mode of 
analysis has already resulted in the addition of three new metals. 
But the most astonishing of Kirchoff’s discoveries is the detection of 
sodium, nickel, barium and copper in the solar atmosphere. The pro- 
cess has also been applied to the fixed stars and Donati has com- 
pared the refractive powers of stellar and solar light. 
When we consider the magnitude of these sublime discoveries and the 
variety of their probable results, we cannot but look with admiration and 
with gratitude on the wondrous powers of the human intellect— that 
mighty instrument with which our Almighty creator has equipped us. 
With it we have bound the hostile elements, fire and water, in amity 
together and have yoked them in iron harness to execute our will ; 
with it we have descended into this globe of ours; classed its stratifi- 
cations ; analyzed its natural history ; investigated its age; and even 
ventured to pourtray, in ideal sketches, the principal features of the 
primeeval landscape : with it we have explored the depths of ocean and 
laid down the elevations and depressions of its bed in charts of 
submarine geography: with it we have ascended into heaven and 
mapped down the courses of the bright luminaries that stud its vault: 
with it we have brought under our cognizance the composition of the 
physical source of light, and are able to pronounce, with the certainty 
of Science, on the constituent elements of a body 95,000,000 of miles 
removed from us, through the aid of an analysis so subtle that on 
