[ S91 ] 
XIV. On Radiant Matter Spectroscopy .—Part II. Samarium. 
By William Crookes, F.R.S. 
Received May 21,—Read June 18, 1885. 
[Plate 75.] 
Introduction. 
90. In the concluding sentence of the Bakerian Lecture which I had the honour to 
deliver before the Royal Society, May 31, 1883, I said that the new method of 
Radiant Matter Spectroscopy there described had given me not only spectrum indica¬ 
tions of the presence of yttrium as an almost invariable, though very minute, con¬ 
stituent of a large number of minerals, but had likewise revealed signs of another 
spectrum-yielding element. I stated that I had repeatedly seen indications of another 
very beautiful spectrum characterised by a strong red and a double orange band. 
That this second spectrum was not then new to me is shown by a paper sent to the 
Royal Society in 1881,'“ in which I described a double orange band occurring in the 
phosphorescent spectrum of an earth less frequently met with than the “ pale yellowish 
coloured earth ” (since identified as yttria) which gave me the “ red, orange, citron, and 
green bands.” 
Fig. 1. 
91. The method adopted to bring out the orange band is to treat the substance 
under examination with strong sulphuric acid, drive off excess of acid by heat, and 
finally to raise the temperature to dull redness. It is then put into a radiant matter 
tube, of the form shown in fig. 1, and the induction spark is passed through it after 
the exhaustion has been pushed to the required degree. The anhydrous sulphate thus 
* Proc. Roy. Soc., vol. xxxii. (1881), p. 206. 
