914 
MR. W. CROOKES ON RADIANT MATTER SPECTROSCOPY: 
of the alkaline earths. The spectrum is best seen under low dispersion and not too 
narrow a slit. The accompanying cut gives an accurate map of the spectrum. I have 
given in line No. 1 the position of the principal Fraunhofer lines for comparison 
of position. Line No. 2 gives the position of the bands, and No. 3 the relative 
intensities represented by the heights of the ordinates. The numbers along the top 
refer to a scale of squared oscillation frequencies, or of the squared reciprocals of wave 
lengths. 
72. Commencing at the red end, two narrow faint bands are seen at 2245 and 
2275, followed by a stronger and broader red band extending between 2355 and 
2415. Another faint band occurs between 2577 and 2610, followed after a very 
narrow black interval by a stronger reddish-orange band extending to 2627. Another 
faint orange band occurs at about 28(JO, with edges too indistinct for measurement. 
At about 2940 a faint yellow band appears, extending to about 3025. The strong 
citron-coloured band follows closely from 3028 to 3049 ; and a little further on, 
between 3100 and 3120, a much fainter citron band is seen. Two characteristic 
green bands follow after a dark interval ; the first, very bright, extending between 
3312 and 3320, but shading off on each side ; the second somewhat fainter, but more 
sharply defined than the first, extending from 3420 to 3440; there is also a third faint 
green band, between 3460 and 3467. At 3730 is the centre of a narrow and faint 
