TABLE 18O. 



WAVE-LENGTHS OF FRAUNHOFER LINES. 



For convenience of reference the values of the wave-lengths corresponding to the Fraunhofer lines usually designated 

 by the letters in the column headed " index letters," are here tabulated separately. The values are in ten mil- 

 lionths of a millimetre on the supposition that the D line value is 5896.156. The table is for the most part taken 

 from Rowland's table of standard wave-lengths, but when no corresponding wave-length is there given, the number 

 given by Kayser and Runge has been taken. These latter are to two places of decimals. 



* The two lines here given for A are stated by Rowland to be : the first, a line " beginning at the head of A, out- 

 side edge; " the second, a "single line beginning at the tail of A." 

 t The principal line in the head of B. 

 t Chief line in the a group. 

 Ames, " Phil. Mag." (5) vol. 30. 



II Cornu gives 3179.8, which, allowing for the different value of the standard D line, corresponds to about 3180.3. 

 IT Cornu gives 3144.7, which would correspond to about 3145.2. 



SMITHSONIAN TABLES. 



175 



