206 



From Newton to Kirchoff. 



into his darkened chamber, Fraunhofer made a narrow- 

 slit, and, receiving upon his prism the slice of sunlight thus 

 obtained, he beheld a new and startling revelation. The 

 brilliant spectrum, now somewhat subdued, gave up a 

 secret. Its colors were not continuous ; thickly distributed 

 throughout its entire length were a multitude of bars of 

 darkness. Six hundred of these delicate tracings the 

 enthusiastic discoverer patiently counted, and finding that 

 each one held a definite place among the colors where it 

 could be found at all times when properly sought, he gave 

 names to several of those most plainly seen and proceeded 

 to map the spectrum with such conscientious care that in 

 the more searching examinations by means of far more 

 perfect instruments in .later times, it has not been found 

 necessary to change the position of a single line which he 

 laid down. Since his time, as methods of research have 

 been refined, a multitude of dark lines, unseen by Fraun- 

 hofer have been discovered. As clearly cut and as well 

 defined as if the delicate brush of a most skillful artist had 

 been drawn across the spectrum ? they span the colors in 

 parallel bars at intervals so minute that the dispersion of 

 several prisms followed up by the magnifying power of a 

 telescope is needed to enable the eye to see the distance 

 between them. Thirteen years before the discovery of 

 these dark lines by Fraunhofer, the celebrated Dr. Wol- 

 laston had announced the existence of two, but the pheno- 

 menon, so delicate and, as left by him, so apparently use- 

 less, was in danger of being altogether forgotten. But to 

 Wollaston and not to Fraunhofer, the dark lines of the 

 spectrum first appeared, and to scientists of a later day 

 belongs the credit of swelling the number known from 

 Fraunhofer's six hundred up to several thousands. In the 

 face of all this, the dark lines of the spectrum are univer- 

 sally known as Fraunhofer' s lines, scientists by common 

 consent bestowing this honor upon that careful observer, 



