MR. W. CROOKES OK RADIANT MATTER SPECTROSCOPY. 
715 
yttria 65—the only indication that could now be found of the samarium spectrum was 
seen in the two faint green bands next to the citron line of yttria, a faint yellow band, 
and the new orange line, which shone out as brightly and sharply as ever. 
The series was continued :— 
Samaria. 
Yttria. 
30 
70 
25 
75 
20 
80 
10 
90 
5 
95 
In each case a careful map of the spectrum was taken on the — scale, and each spec¬ 
trum was found to be practically identical. Slight differences in the relative intensities 
of some of the bands were observed ; but the general character of the spectrum was 
unaltered. The yttria spectrum now shone forth with scarcely any band of samaria, 
except that, standing out beyond the other bands in sharpness and brilliancy, the 2693 
line was present in all. 
150. It will be remarked that a sudden change occurs between the two mixtures, 
samaria 45, yttria 55, and samaria 35, yttria 65 ; on one side the spectrum pertains to 
that of samaria, whilst on the other side the spectrum is that of yttria, the new orange 
line running equally across them all. 
Fig. 7. 
Fig. 8. 
151. The diagrams of some of these intermediate spectra shown in the accompany- 
mg figures illustrate how sudden is the transformation from the samarium to the 
yttrium spectrum. Fig. 7 is the spectrum of a mixture of 44 parts samaria and 56 
parts yttria, and except for the increased strength of the orange line, and a faint trace 
of the red and yellow yttria bands, it is the pure samarium spectrum. Fig. 8 is the 
