ON CATALOGITES OF SPECTRAL RAYS. 



55 



tiplied by 10^. Each number iu this column is accordingly the number of 

 times that the corresponding wave-length in air goes into one millimetre. 



Column 4 contains the correction for the dispersion of air of 760 millims. 

 pressure and 16° temperature, deduced from Ketteler's observations (see Phil. 

 Mag. for 1866, vol. xxxii. p. 336). 



Column 5 contains the Standard Wave-numbers, i. e. the number of waves 

 per millimetre in vacuo. 



Column 6 indicates the intensity and width of each ray as determined by 

 KirchhofF, 6 being the most intense, and g very wide, viz. about 0-15 of one 

 degree on the Scale of Standard "Wave-numbers. 



Column 7 enumerates the substances which have been found to emit bright 

 rays coincide at with solar lines, and contains some other remarks. 



Column 8. In the last column the rays are bracketed into the groups 

 which strike the eye in looking at the spectrum, and to each group is assigned 

 a number which sufficiently indicates its position upon the Standard Scale. 



