When Kirchhoff thrust between the image of 

 the sun from the heliostat and the tinted band 

 of his spectroscope, a flame of sodium vapor, and, 

 instead of the expected brightening, saw the band 

 darkened, he left his laboratory hastily with the 

 words: " That seems to me a fundamental fact." 

 He had demonstrated that in the atmosphere of 

 the distant sun, vapor of sodium was present; he 

 had established a relation between this far-away 

 star and the Fraunhofer lines. 



WIENER, Die Eru'citcrung unserer Sinne. 



The domain of the senses, in nature, is almost 

 infinitely small in comparison with the vast re- 

 gion accessible to thought which lies beyond 

 them. From a few observations of a comet, 

 when it comes within the range of his telescope, 

 an astronomer can calculate its path in regions 

 which no telescope can reach; and in like man- 

 ner, by means of data furnished in the narrow 

 world of the senses, we make ourselves at home 

 in other and wider worlds, which are traversed 

 by the intellect alone. 



TYNDALL, On Radiant Heat. 



