1885.] 



On Bad/ ant Matter Spectroscoj>y. 



419 



out, the spectrum is seen to consist of three bright bands, — red, orange, 

 and green, — nearly equidistant, the orange being the brightest. With a 

 narrower slit the orange and green bands are seen to be double, and on 

 closer examination faint wings are seen, like shadows to the orange 

 and green bands. 



Preliminary experiments had shown me that lime was one of the 

 best materials to mix with samaria in order to bring out its phosphor- 

 escent spectrum, but it was by no means the only body which would 

 have the desired effect. 



The samarium spectra, modified by other metals, may be divided 

 into three groups. The first group comprises the spectra given when 

 glucinum, magnesium, zinc, cadmium, lanthanum, bismuth, or anti- 

 mony is mixed with the samarium. It consists simply of three 

 coloured bands, red, orange, and green ; as a typical illustration I will 

 select the lanthanum- samarium spectrum (fig. 1). 



The second type of spectrum gives a single red and orange and a 

 double green band. This is produced when barium, strontium, tho- 

 rium, or lead, is mixed with samarium. The lead-samarium spectrum 

 (fig. 2) illustrates this type. 



Fig. 2. 



The third kind of spectrum is given by calcium mixed with sama- 

 rium. Here the red and green are single, and the orange double. 

 Aluminium would also fall into this class were it not that the broad 

 ill- defined green band is also doubled. The calcium-samarium spec- 

 trum (fig. 3) is a good illustration of this type. 



VOL. xxxviii. 2 H 



