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any forward step was made to unravel their mysteries. In the inves- 

 tigation of the laws of light and heat it has, in these latter years, made 

 marvelous advances. 



Some of the recent discoveries in this field are so wonderful, and at the 

 same time so beautiful, that I feel tempted to explain a few of them this 

 evening, very briefly however, for the benefit of those of our members 

 who may not have had time to become acquainted with them. 



Newton discovered that when a beam of light was passed through a 

 •denser medium than the air it was refracted or bent, in its passage through 

 the denser medium, out of a direct line. When the beam was passed 

 through a glass prism, he discovered that some of its rays were bent more 

 than others, and thus became separated beyond the prism, and that when 

 thus separated these rays were of different colors, and when thrown upon 

 a screen the colors were ranged in the order in which we see them in the 

 rainbow. 



The colors thus produced by the dispersion or separation of the rays 

 of a beam of sunlight, are usually known by the name of "The Solar 

 Spectrum." 



Newton found, also, that by passing these colored rays back through 

 another prism, suitably placed, they became combined again, and then 

 -appeared, as before, in a single beam of white or colorless light. 



In this alternate analysis and synthesis of light did Newton ponder. 

 •He had made the first great step in the investigation of its marvelous phe- 

 nomena, but even his giant intellect could advance no further in solving 

 its mysteries. 



The anatomy of the silken tresses which grace the brow of a rustic 

 maiden are to her no more mysterious than were those pencils of light to 

 'the mind of Newton. She may spread out her flowing wealth in the sun- 

 shine, and wonder at its lustrous beauty, but she can no more number 

 each one of its single fibres than could Newton count the threads which 

 came to him in that beam from the distant orb of day. To her the mys- 

 tery of its growth, the cunning workmanship of its roots, the delicate 

 architecture of its fairy-like chambers, and the pristine fluid that for a few 

 brief years will circulate within its tiny channels and keep the snow-flakes 

 •of age from dimming its raven sheen, are no less unknown, than were the 

 scores of fascinating truths we now possess respecting light unknown to 

 that great philospher. Yet this was the first grand step toward those 

 wonders which have culminated within the last twelve years in the aston- 

 ishing revelations of the spectroscope. 



Subsequent philosophers, investigating the solar spectrum thus spread 

 out by Newton, discovered that when the thermometer was exposed in the 

 variously-colored rays in succession, from the violet to the red, the mer- 

 cury rose gradually and attained its greatest height within the red rays. 

 Continuing still further with it in that direction, the remarkable discovery 

 was made, that the mercury rose much more rapidly beyond the red where 

 no color whatever was visible. Thus was the curious fact discovered, 

 that the sun emitted certain rays incapable of exciting vision, yet possess- 



